\section{Database classes overview}\label{odbcoverview}
\normalboxd{The more sophisticated wxODBC classes (wxDb/wxDbTable) are the
-recommended classes for doing database/ODBC work with wxWindows. These new
-classes replace the wxWindows v1.6x classes wxDatabase. Documentation for the
+recommended classes for doing database/ODBC work with wxWindows. These new
+classes replace the wxWindows v1.6x classes wxDatabase. Documentation for the
old wxDatabase class and its associated classes is still
included in the class documentation and in this overview section, but support
for these old classes has been phased out, and all future development work
\subsection{Different ODBC Class Libraries in wxWindows}
-Following is detailed overview of how to use the wxWindows ODBC classes - \helpref{wxDb}{wxdb}
-and \helpref{wxDbTable}{wxdbtable} and their associated functions. These are
+Following is a detailed overview of how to use the wxWindows ODBC classes - \helpref{wxDb}{wxdb}
+and \helpref{wxDbTable}{wxdbtable} and their associated functions. These are
the ODBC classes donated by Remstar International, and are collectively
-referred to herein as the wxODBC classes. Since their initial inclusion with
+referred to herein as the wxODBC classes. Since their initial inclusion with
wxWindows v2.x, they have become the recommended wxWindows classes for database
access.
An older version of some classes ported over from wxWindows v1.68 still exist
(see \helpref{wxDatabase}{wxdatabase} in odbc.cpp), but are now deprecated in favor of the more
-robust and comprehensive wxDb/wxDbTable classes. All current and future
+robust and comprehensive wxDb/wxDbTable classes. All current and future
feature development, as well as active debugging, are only being done on
-the wxODBC classes. Documentation for the older classes is still provided
-in this manual. The \helpref{wxDatabase overview}{wxdatabaseoverview} of the
+the wxODBC classes. Documentation for the older classes is still provided
+in this manual. The \helpref{wxDatabase overview}{wxdatabaseoverview} of the
older classes follows the overview of the new classes.
\subsection{wxDb/wxDbTable wxODBC Overview}\label{wxodbcoverview}
Classes: \helpref{wxDb}{wxdb}, \helpref{wxDbTable}{wxdbtable}
-The wxODBC classes were designed for database independence. Although SQL and
+The wxODBC classes were designed for database independence. Although SQL and
ODBC both have standards which define the minimum requirements they must
support to be in compliance with specifications, different database vendors
-may implement things slightly different. One example of this is that Oracle
+may implement things slightly differently. One example of this is that Oracle
requires all user names for the datasources to be supplied in uppercase
-characters. In situations like this, the wxODBC classes have been written
+characters. In situations like this, the wxODBC classes have been written
to make this transparent to the programmer when using functions that require
-database specific syntax.
+database-specific syntax.
Currently several major databases, along with other widely used databases,
-have been tested and supported through the wxODBC classes. The list of
+have been tested and supported through the wxODBC classes. The list of
supported databases is certain to grow as more users start implementing
software with these classes, but at the time of the writing of this document,
users have successfully used the classes with the following datasources:
\helpref{wxDBMS}{wxdbenumeratedtypes} in db.h.
**dBase is not truly an ODBC datasource, but there are drivers which can
-emulate much of the functionality of an ODBC connection to a dBase table.
+emulate much of the functionality of an ODBC connection to a dBase table.
See the \helpref{wxODBC Known Issues}{wxodbcknownissues} section of this
overview for details.
\subsection{wxODBC Where To Start}\label{wxodbcwheretostart}
First, if you are not familiar with SQL and ODBC, go to your local bookstore
-and pick up a good book on each. This documentation is not meant to teach
+and pick up a good book on each. This documentation is not meant to teach
you many details about SQL or ODBC, though you may learn some just from
immersion in the subject.
If you have worked with non-SQL/ODBC datasources before, there are some
-things you will need to un-learn. First some terminology as these phrases will
+things you will need to un-learn. First some terminology as these phrases will
be used heavily in this section of the manual.
\begin{twocollist}\itemsep=0pt
commands sent by your application and converts them to the SQL format expected
by the target datasource.}
\twocolitem{Datasource connection}{An open pipe between your application and
-the ODBC driver which in turn has a connection to the target datasource.
+the ODBC driver which in turn has a connection to the target datasource.
Datasource connections can have a virtually unlimited number of wxDbTable
-instances using the same connect (dependent on the ODBC driver). A separate
+instances using the same connect (dependent on the ODBC driver). A separate
connection is not needed for each table (the exception is for isolating
commits/rollbacks on different tables from affecting more than the desired
-table. See the class documentation on
+table. See the class documentation on
\helpref{wxDb::CommitTrans}{wxdbcommittrans} and
-\helpref{wxDb::RollbackTrans}{wxdbrollbacktrans}.}
+\helpref{wxDb::RollbackTrans}{wxdbrollbacktrans}.)}
\twocolitem{Rows}{Similar to records in old relational databases, a row is a
collection of one instance of each column of the data table that are all
associated with each other.}
\twocolitem{Columns}{Individual fields associated with each row of a data
table.}
\twocolitem{Query}{Request from the client to the datasource asking for
-the data that matches the requirements specified in the users request. When
+the data that matches the requirements specified in the users request. When
a query is performed, the datasource performs the lookup of the rows with
satisfy the query, and creates a result set.}
\twocolitem{Result set}{The data which matches the requirements specified
-in a query sent to the datasource. Dependent on drivers, a result set
+in a query sent to the datasource. Dependent on drivers, a result set
typically remains at the datasource (no data is transmitted to the ODBC driver)
until the client actually instructs the ODBC driver to retrieve it.}
-\twocolitem{Cursor}{a logical pointer into the result set that a query
+\twocolitem{Cursor}{A logical pointer into the result set that a query
generates, indicating the next record that will be returned to the client
when a request for the next record is made.}
\twocolitem{Scrolling cursors}{Scrolling refers to the movement of cursors
-through the result set. Cursors can always scroll forward sequentially in
-the result set (FORWARD ONLY scrolling cursors). With Forward only scrolling
+through the result set. Cursors can always scroll forward sequentially in
+the result set (FORWARD ONLY scrolling cursors). With Forward only scrolling
cursors, once a row in the result set has been returned to the ODBC driver
and on to the client, there is no way to have the cursor move backward in
the result set to look at the row that is previous to the current row in
-the result set. If BACKWARD scrolling cursors are supported by both the
+the result set. If BACKWARD scrolling cursors are supported by both the
ODBC driver and the datasource that are being used, then backward
scrolling cursor functions may be used (
\helpref{wxDbTable::GetPrev}{wxdbtablegetprev},
\helpref{wxDbTable::GetFirst}{wxdbtablegetfirst}, and
-\helpref{wxDbTable::GetLast}{wxdbtablegetlast}). If the datasource or the
+\helpref{wxDbTable::GetLast}{wxdbtablegetlast}). If the datasource or the
ODBC driver only support forward scrolling cursors, your program and logic
must take this in to account.}
\twocolitem{Commit/Rollback}{Commit will physically save
insertions/deletions/updates, while rollback basically does an undo of
everything done against the datasource connection that has not been
-previously committed. Note that Commit and Rollbacks are done on a
-connection, not on individual tables. All tables which use a shared
+previously committed. Note that Commit and Rollbacks are done on a
+connection, not on individual tables. All tables which use a shared
connection to the datasource are all committed/rolled back at the same
time when a call to
\helpref{wxDb::CommitTrans}{wxdbcommittrans} or
\helpref{wxDb::RollbackTrans}{wxdbrollbacktrans} is made.}
-\twocolitem{Index}{Indexes are datasource maintained lookup structures
+\twocolitem{Index}{Indexes are datasource-maintained lookup structures
that allow the datasource to quickly locate data rows based on the values
-of certain columns. Without indexes, the datasource would need to do a
-sequential search of a table every time a query request is made. Proper
+of certain columns. Without indexes, the datasource would need to do a
+sequential search of a table every time a query request is made. Proper
unique key index construction can make datasource queries nearly instantaneous.}
\end{twocollist}
Before you are able to read data from a data table in a datasource, you must
-have a connection to the datasource. Each datasource connection may be used
+have a connection to the datasource. Each datasource connection may be used
to open multiple tables all on the same connection (number of tables open are
dependent on the driver, datasource configuration and the amount of memory on
-the client workstation). Multiple connections can be opened to the same
+the client workstation). Multiple connections can be opened to the same
datasource by the same client (number of concurrent connections is dependent
on the driver and datasource configuration).
When a query is performed, the client passes the query to the ODBC driver,
-and the driver then translates it and passes it along to the datasource. The
+and the driver then translates it and passes it along to the datasource. The
database engine (in most cases - exceptions are text and dBase files) running
on the machine hosting the database does all the work of performing the search
-for the requested data. The client simply waits for a status to come back
-through the ODBC driver from the datasource.
+for the requested data. The client simply waits for a status to come back
+through the ODBC driver from the datasource.
Depending on the ODBC driver, the result set either remains "queued" on the
database server side, or is transferred to the machine that the driver is
-queued on. The client does not receive this data. The client must request
+queued on. The client does not receive this data. The client must request
some or all of the result set to be returned before any data rows are
returned to the client application.
Result sets do not need to include all columns of every row matching the
-query. In fact, result sets can actually be joinings of columns from two
+query. In fact, result sets can actually be joinings of columns from two
or more data tables, may have derived column values, or calculated values
returned.
For each result set, a cursor is maintained (typically by the database)
-which keeps track of where in the result set the user currently is.
+which keeps track of where in the result set the user currently is.
Depending on the database, ODBC driver, and how you configured the
wxWindows ODBC settings in setup.h (see \helpref{wxODBC - Compiling}{wxodbccompiling}), cursors can be
-either forward or backward scrolling. At a minim, cursors must scroll
-forward. For example, if a query resulted in a result set with 100 rows,
+either forward or backward scrolling. At a minimum, cursors must scroll
+forward. For example, if a query resulted in a result set with 100 rows,
as the data is read by the client application, it will read row 1, then 2,
-then 3, etc, etc. With forward only cursors, once the cursor has moved to
+then 3, etc. With forward only cursors, once the cursor has moved to
the next row, the previous row cannot be accessed again without re-querying
-the datasource for the result set over again. Backward scrolling cursors
+the datasource for the result set over again. Backward scrolling cursors
allow you to request the previous row from the result set, actually
scrolling the cursor backward.
Backward scrolling cursors are not supported on all database/driver
-combinations. For this reason, forward-only cursors are the default in
-the wxODBC classes. If your datasource does support backward scrolling
+combinations. For this reason, forward-only cursors are the default in
+the wxODBC classes. If your datasource does support backward scrolling
cursors and you wish to use them, make the appropriate changes in setup.h
-to enable them (see \helpref{wxODBC - Compiling}{wxodbccompiling}). For greatest portability between
+to enable them (see \helpref{wxODBC - Compiling}{wxodbccompiling}). For greatest portability between
datasources, writing your program in such a way that it only requires
-forward scrolling cursors is your best bet. On the other hand, if you are
+forward scrolling cursors is your best bet. On the other hand, if you are
focusing on using only datasources that support backward scrolling cursors,
potentially large performance benefits can be gained from using them.
There is a limit to the number of cursors that can be open on each connection
to the datasource, and usually a maximum number of cursors for the datasource
-itself. This is all dependent on the database. Each connection that is
-opened (each instance of a wxDb) opens a minimum of 5 cursors for on creation
-that are required for things such as updates/deletions/rollbacks/queries.
+itself. This is all dependent on the database. Each connection that is
+opened (each instance of a wxDb) opens a minimum of 5 cursors on creation
+that are required for things such as updates/deletions/rollbacks/queries.
Cursors are a limited resource, so use care in creating large numbers of
cursors.
Additional cursors can be created if necessary with the
-\helpref{wxDbTable::GetNewCursor}{wxdbtablegetnewcursor} function. One example
-use for additional cursors are to track multiple scroll points in result
-sets. By creating a new cursor, a program could request a second result set
+\helpref{wxDbTable::GetNewCursor}{wxdbtablegetnewcursor} function. One example
+use for additional cursors is to track multiple scroll points in result
+sets. By creating a new cursor, a program could request a second result set
from the datasource while still maintaining the original cursor position in
the first result set.
insertion, deletion, or update (or other SQL functions like altering
tables, etc) through ODBC, the program must issue a "commit" to the
datasource to tell the datasource that the action(s) it has been told to
-perform are to be recorded as permanent. Until a commit is performed,
+perform are to be recorded as permanent. Until a commit is performed,
any other programs that query the datasource will not see the changes that
have been made (although there are databases that can be configured to
-auto-commit). NOTE: With most all datasources, until the commit is
+auto-commit). NOTE: With most datasources, until the commit is
performed, any cursor that is open on that same datasource connection
-will be able to see the changes that are uncommitted. Check your
-database's documentation/configuration to verify this before counting on it
+will be able to see the changes that are uncommitted. Check your
+database's documentation/configuration to verify this before relying on it
though.
-A rollback is basically an UNDO command on the datasource connection. When
+A rollback is basically an UNDO command on the datasource connection. When
a rollback is issued, the datasource will flush all commands it has been told
to do since the last commit that was performed.
NOTE: Commits/Rollbacks are done on datasource connections (wxDb instances)
-not on the wxDbTable instances. This means that if more than one table
+not on the wxDbTable instances. This means that if more than one table
shares the same connection, and a commit or rollback is done on that
connection, all pending changes for ALL tables using that connection are
committed/rolled back.
-
-
\subsection{wxODBC - Configuring your system for ODBC use}\label{wxodbcconfiguringyoursystem}
Before you are able to access a datasource, you must have installed and
-configured an ODBC driver. Doing this is system specific, so it will not be
-covered in detail here. But here are a few details to get you started.
+configured an ODBC driver. Doing this is system specific, so it will not be
+covered in detail here. But here are a few details to get you started.
Most database vendors provide at least a minimal ODBC driver with their
-database product. In practice, many of these drivers have proven to be slow
-and/or incomplete. Rumor has it that this is because the vendors do not want
-you using the ODBC interface to their products, they want you to use their
-applications to access the data.
-
-Whatever the reason, for database intensive applications, you may want to
-think of using a third-party ODBC driver for your needs. One example of a
-third party set of ODBC drivers that has been heavily tested and used is
-Rogue Wave's drivers. Rogue Wave has drivers available for many different
+database product. In practice, many of these drivers have proven to be slow
+and/or incomplete. Rumour has it that this is because the vendors do not want
+you using the ODBC interface to their products; they want you to use their
+applications to access the data.
+
+Whatever the reason, for database-intensive applications, you may want to
+consider using a third-party ODBC driver for your needs. One example of a
+third-party set of ODBC drivers that has been heavily tested and used is
+Rogue Wave's drivers. Rogue Wave has drivers available for many different
platforms and databases.
-Under Microsoft Windows, install the ODBC driver you are planning to use. You
+Under Microsoft Windows, install the ODBC driver you are planning to use. You
will then use the ODBC Administrator in the Control Panel to configure an
-instance of the driver for your intended datasource. Note that with all
+instance of the driver for your intended datasource. Note that with all
flavors of NT, this configuration can be set up as a System or User DSN
-(datasource name). Configuring it as a system resource will make it
+(datasource name). Configuring it as a system resource will make it
available to all users (if you are logged in as 'administrator'), otherwise
-the datasource will only be available to the who configured the DSN.
+the datasource will only be available to the user who configured the DSN.
-Under Unix, iODBC is used for implementation of the ODBC API. To compile the
-wxODBC classes, you must first obtain (http://www.iodbc.org) and install iODBC.
-Then you must create the file "~/.odbc.ini" (or optionally create
-"/etc/odbc.ini" for access for all users on the system). This file contains
-the settings for your system/datasource. Below is an example section of a
+Under Unix, iODBC is used for implementation of the ODBC API. To compile the
+wxODBC classes, you must first obtain iODBC from \urlref{http://www.iodbc.org}{www.iodbc.org} and install it.
+(Note: wxWindows currently includes a version of iODBC.) Then you must create the file "~/.odbc.ini" (or optionally create
+"/etc/odbc.ini" for access for all users on the system). This file contains
+the settings for your system/datasource. Below is an example section of a
odbc.ini file for use with the "samples/db" sample program using MySQL:
\begin{verbatim}
PORT = 3306
\end{verbatim}
-
-
\subsection{wxODBC - Compiling}\label{wxodbccompiling}
The wxWindows setup.h file has several settings in it pertaining to compiling
\begin{twocollist}\itemsep=0pt
\twocolitem{wxUSE\_ODBC}{This must be set to 1 in order for the compiler to
-compile the wxODBC classes. Without setting this to 1, there will be no
-access to any of the wxODBC classes. The default is 0.}
+compile the wxODBC classes. Without setting this to 1, there will be no
+access to any of the wxODBC classes. The default is 0.}
\twocolitem{wxODBC\_FWD\_ONLY\_CURSORS}{When a new database connection is
requested, this setting controls the default of whether the connection allows
only forward scrolling cursors, or forward and backward scrolling cursors
(see the section in "WHERE TO START" on cursors for more information on
-cursors). This default can be overridden by passing a second parameter to
+cursors). This default can be overridden by passing a second parameter to
either the \helpref{wxDbGetConnection}{wxdbfunctions} or
-\helpref{wxDb constructor}{wxdbconstr}. The default is 1.}
+\helpref{wxDb constructor}{wxdbconstr}. The default is 1.}
\twocolitem{wxODBC\_BACKWARD\_COMPATABILITY}{Between v2.0 and 2.2, massive
renaming efforts were done to the ODBC classes to get naming conventions
similar to those used throughout wxWindows, as well as to preface all wxODBC
-classes names and functions with a wxDb preface. Because this renaming would
+classes names and functions with a wxDb preface. Because this renaming would
affect applications written using the v2.0 names, this compile-time directive
was added to allow those programs written for v2.0 to still compile using the
-old naming conventions. These deprecated names are all #define'd to their
+old naming conventions. These deprecated names are all {\tt\#}define'd to their
corresponding new function names at the end of the db.cpp/dbtable.cpp source
-files. These deprecated class/function names should not be used in future
-development, as at some point in the future they will be removed. The default
+files. These deprecated class/function names should not be used in future
+development, as at some point in the future they will be removed. The default
is 0.}
\end{twocollist}
{\it Under MS Windows}
You are required to include the "odbc32.lib" provided by your compiler vendor
-in the list of external libraries to be linked in. If using the makefiles
+in the list of external libraries to be linked in. If using the makefiles
supplied with wxWindows, this library should already be included for use with
makefile.b32, makefile.vc, and makefile.g95.
\normalbox{MORE TO COME}
-
-
\subsection{wxODBC - Basic Step-By-Step Guide}\label{wxodbcstepbystep}
To use the classes in an application, there are eight basic steps:
Following each of these steps is detailed to explain the step, and to
hopefully mention as many of the pitfalls that beginning users fall in
-to when first starting to use the classes. Throughout the steps, small
-snippets of code are shown to show the syntax of performing the step. A
+to when first starting to use the classes. Throughout the steps, small
+snippets of code are provided to show the syntax of performing the step. A
complete code snippet is provided at the end of this overview that shows a
complete working flow of all these steps (see
-\helpref{wxODBC - Sample Code #1}{wxodbcsamplecode1}).
-
+\helpref{wxODBC - Sample Code {\tt\#}1}{wxodbcsamplecode1}).
{\bf Define datasource connection information}
To be able to connect to a datasource through the ODBC driver, a program must
supply a minimum of three pieces of information: Datasource name, User ID, and
-Authorization string (password). A fourth piece of information, a default
+Authorization string (password). A fourth piece of information, a default
directory indicating where the data file is stored, is required for Text and
dBase drivers for ODBC.
values, plus some others that may be desired.
The 'Henv' member is the environment handle used to access memory for use by the
-ODBC driver. Use of this member is described below in the "Getting a Connection
+ODBC driver. Use of this member is described below in the "Getting a Connection
to the Datasource" section.
The 'Dsn' must exactly match the datasource name used to configure the ODBC
datasource (in the ODBC Administrator (MSW only) or in the .odbc.ini file).
-The 'Uid' is the User ID that is to be used to log in to the datasource. This
+The 'Uid' is the User ID that is to be used to log in to the datasource. This
User ID must already have been created and assigned rights within the
-datasource to which you are connecting. The user that the connection is
+datasource to which you are connecting. The user that the connection is
establish by will determine what rights and privileges the datasource
connection will allow the program to have when using the connection that
-this connection information was used to establish. Some datasources are
+this connection information was used to establish. Some datasources are
case sensitive for User IDs, and though the wxODBC classes attempt to hide
this from you by manipulating whatever data you pass in to match the
datasource's needs, it is always best to pass the 'Uid' in the case that
the datasource requires.
-The 'AuthStr' is the password for the User ID specified in the 'Uid' member.
-As with the 'Uid', some datasources are case sensitive (in fact most are).
-The wxODBC classes do NOT try to manage the case of the 'AuthStr' at all.
+The 'AuthStr' is the password for the User ID specified in the 'Uid' member.
+As with the 'Uid', some datasources are case sensitive (in fact most are).
+The wxODBC classes do NOT try to manage the case of the 'AuthStr' at all.
It is passed verbatim to the datasource, so you must use the case that the
datasource is expecting.
The 'defaultDir' member is used with file based datasources (i.e. dBase,
-FoxPro, text files). It contains a full path to the location where the
-data table or file is located. When setting this value, use forward
+FoxPro, text files). It contains a full path to the location where the
+data table or file is located. When setting this value, use forward
slashes '/' rather than backslashes '\' to avoid compatibility differences
between ODBC drivers.
-The other fields are currently unused. The intent of these fields are that
+The other fields are currently unused. The intent of these fields are that
they will be used to write our own ODBC Administrator type program that will
-work on both MSW and Un*x systems, regardless of the datasource. Very little
+work on both MSW and Un*x systems, regardless of the datasource. Very little
work has been done on this to date.
-
{\bf Get a Datasource Connection}
-There are two methods of establishing a connection to a datasource. You
+There are two methods of establishing a connection to a datasource. You
may either manually create your own wxDb instance and open the connection,
or you may use the caching functions provided with the wxODBC classes to
create/maintain/delete the connections.
Regardless of which method you use, you must first have a fully populated
-wxDbConnectInf object. In the wxDbConnectInf instance, provide a valid
-Dns, Uid, and AuthStr (along with a 'defaultDir' if necessary). Before
+wxDbConnectInf object. In the wxDbConnectInf instance, provide a valid
+Dns, Uid, and AuthStr (along with a 'defaultDir' if necessary). Before
using this though, you must allocate an environment handle to the 'Henv'
member.
\end{verbatim}
When the wxDbConnectInf::AllocHenv() function is called successfully, a
-value of TRUE will be returned. A value of FALSE means allocation failed,
+value of TRUE will be returned. A value of FALSE means allocation failed,
and the handle will be undefined.
A shorter form of doing the above steps is encapsulated into the
This shorthand form of initializing the constructor passes a NULL for the SQL
environment handle, telling the constructor to allocate a handle during
-construction. This handle is also managed for the life of wxDbConnectInf
+construction. This handle is also managed for the life of wxDbConnectInf
instance, and is freed automatically upon destruction of the instance.
Once the wxDbConnectInf instance is initialized, you are ready to
\end{verbatim}
The first line does the house keeping needed to initialize all
-the members of the wxDb class. The second line actually sends the request
+the members of the wxDb class. The second line actually sends the request
to the ODBC driver to open a connection to its associated datasource using
the parameters supplied in the call to \helpref{wxDb::Open}{wxdbopen}.
-A more advanced form of opening a connection is to used the connection
-caching functions that are included with the wxODBC classes. The caching
-mechanisms do the same functions are the manual approach to opening a
+A more advanced form of opening a connection is to use the connection
+caching functions that are included with the wxODBC classes. The caching
+mechanisms perform the same functions as the manual approach to opening a
connection, but they also manage each connection they have created,
re-using them and cleaning them up when they are closed, without you
-programmatically needing to do the coding.
+needing to do the coding.
To use the caching function \helpref{wxDbGetConnection}{wxdbfunctions} to get
a connection to a datasource, simply call it with a single parameter of the
db = wxDbGetConnection(DbConnectInf);
\end{verbatim}
-The wxDb pointer that is returned is both initialized and opened. If
+The wxDb pointer that is returned is both initialized and opened. If
something failed in creating or opening the connection, the return value
from \helpref{wxDbGetConnection}{wxdbfunctions} will be NULL.
The connection that is returned is either a new connection, or it is a
"free" connection from the cache of connections that the class maintains
-that was no longer in use. Any wxDb instance created with a call to
-\helpref{wxDbGetConnection}{wxdbfunctions} is kept track of in a linked list of established
-connections. When a program is done with a connection, a call to
+that was no longer in use. Any wxDb instance created with a call to
+\helpref{wxDbGetConnection}{wxdbfunctions} is recorded in a linked list of established
+connections. When a program is finished with a connection, a call to
\helpref{wxDbFreeConnection}{wxdbfunctions} is made, and the datasource
connection will then be tagged as FREE, making it available for the next
call to \helpref{wxDbGetConnection}{wxdbfunctions} that needs a connection
-using the same connection information (Dsn, Uid, AuthStr). The cached
+using the same connection information (Dsn, Uid, AuthStr). The cached
connections remain cached until a call to \helpref{wxDbCloseConnections}{wxdbfunctions} is made,
at which time all cached connections are closed and deleted.
Besides the obvious advantage of using the single command caching routine to
obtain a datasource connection, using cached connections can be quite a
-performance boost as well. Each time that a new connection is created
+performance boost as well. Each time that a new connection is created
(not retrieved from the cache of free connections), the wxODBC classes
perform many queries against the datasource to determine the datasource's
-datatypes and other fundamental behaviors. Depending on the hardware,
+datatypes and other fundamental behaviours. Depending on the hardware,
network bandwidth, and datasource speed, this can in some cases take a
-few seconds to establish the new connection (with well balanced systems,
-it should only be a fraction of a second). Re-using already established
+few seconds to establish the new connection (with well-balanced systems,
+it should only be a fraction of a second). Re-using already established
datasource connections rather than creating/deleting, creating/deleting
-connections can be quite a time saver.
+connections can be quite a time-saver.
-Another time saver is the "copy connection" features of both
-\helpref{wxDb::Open}{wxdbopen} and \helpref{wxDbGetConnection}{wxdbfunctions}.
+Another time-saver is the "copy connection" features of both
+\helpref{wxDb::Open}{wxdbopen} and \helpref{wxDbGetConnection}{wxdbfunctions}.
If manually creating a wxDb instance and opening it, you must pass an existing
connection to the \helpref{wxDb::Open}{wxdbopen} function yourself to gain the performance
-benefit of copying existing connection settings. The
+benefit of copying existing connection settings. The
\helpref{wxDbGetConnection}{wxdbfunctions} function automatically does this
for you, checking the Dsn, Uid, and AuthStr parameters when you request
-a connection for any existing connections that use those same settings.
+a connection for any existing connections that use those same settings.
If one is found, \helpref{wxDbGetConnection}{wxdbfunctions} copies the datasource settings for
datatypes and other datasource specific information that was previously
queried, rather than re-querying the datasource for all those same settings.
-One final note on creating a connection. When a connection is created, it
+One final note on creating a connection. When a connection is created, it
will default to only allowing cursor scrolling to be either forward only,
-or both backward and forward scrolling cursors. The default behavior is
+or both backward and forward scrolling. The default behavior is
determined by the setting {\tt wxODBC\_FWD\_ONLY\_CURSORS} in setup.h when you
-compile the wxWindows library. The library default is to only support
+compile the wxWindows library. The library default is to only support
forward scrolling cursors only, though this can be overridden by parameters
for wxDb() constructor or the \helpref{wxDbGetConnection}{wxdbfunctions}
-function. All datasources and ODBC drivers must support forward scrolling
-cursors. Many datasources support backward scrolling cursors, and many
-ODBC drivers support backward scrolling cursors. Before planning on using
+function. All datasources and ODBC drivers must support forward scrolling
+cursors. Many datasources support backward scrolling cursors, and many
+ODBC drivers support backward scrolling cursors. Before planning on using
backward scrolling cursors, you must be certain that both your datasource
-and ODBC driver fully support backward scrolling cursors. See the small
+and ODBC driver fully support backward scrolling cursors. See the small
blurb about "Scrolling cursors" in the definitions at the beginning of
this overview, or other details of setting the cursor behavior in the wxDb
class documentation.
-
{\bf Create Table Definition}
Data can be accessed in a datasource's tables directly through various
-functions of the wxDb class (see \helpref{wxDb::GetData}{wxdbgetdata}). But to make life much
+functions of the wxDb class (see \helpref{wxDb::GetData}{wxdbgetdata}). But to make life much
simpler, the wxDbTable class encapsulates all of the SQL specific API calls
that would be necessary to do this, wrapping it in an intuitive class of APIs.
Each of the above parameters are described in detail in the wxDbTable
class' description, but one special note here about the fifth
-parameter - queryOnly setting. If a wxDbTable instance is created as
-{\tt wxDB\_QUERY\_ONLY}, then no inserts/deletes/updates are able to be performed
-using this instance of the wxDbTable. Any calls to \helpref{wxDb::CommitTrans}{wxdbcommittrans}
+parameter - the queryOnly setting. If a wxDbTable instance is created as
+{\tt wxDB\_QUERY\_ONLY}, then no inserts/deletes/updates can be performed
+using this instance of the wxDbTable. Any calls to \helpref{wxDb::CommitTrans}{wxdbcommittrans}
or \helpref{wxDb::RollbackTrans}{wxdbrollbacktrans} against the datasource
-connection used by this wxDbTable instance are ignored by this instance. If
+connection used by this wxDbTable instance are ignored by this instance. If
the wxDbTable instance is created with {\tt !wxDB\_QUERY\_ONLY} as shown above,
then all the cursors and other overhead associated with being able to
insert/update/delete data in the table are created, and thereby those
only be read from, not written to, there is a performance benefit (not as
many cursors need to be maintained/updated, hence speeding up access times),
as well as a resource savings due to fewer cursors being created for the
-wxDbTable instance. Also, with some datasources, the number of
-simultaneous cursors is limited.
+wxDbTable instance. Also, with some datasources, the number of
+simultaneous cursors is limited.
When defining the columns to be retrievable by the wxDbTable instance, you
-can specify anywhere from one column up to all columns in the table.
+can specify anywhere from one column up to all columns in the table.
\begin{verbatim}
table->SetColDefs(0, "FIRST_NAME", DB_DATA_TYPE_VARCHAR, FirstName,
(in this example, two columns - one with index 0, one with index 1).
The above lines of code "bind" the datasource columns specified to the
-memory variables in the client application. So when the application
+memory variables in the client application. So when the application
makes a call to \helpref{wxDbTable::GetNext}{wxdbtablegetnext} (or any other function that retrieves
data from the result set), the variables that are bound to the columns will
-have the column value stored into them. See the
+have the column value stored into them. See the
\helpref{wxDbTable::SetColDefs}{wxdbtablesetcoldefs}
class documentation for more details on all the parameters for this function.
The bound memory variables have undefined data in them until a call to a
function that retrieves data from a result set is made
(e.g. \helpref{wxDbTable::GetNext}{wxdbtablegetnext},
-\helpref{wxDbTable::GetPrev}{wxdbtablegetprev}, etc). The variables are not
+\helpref{wxDbTable::GetPrev}{wxdbtablegetprev}, etc). The variables are not
initialized to any data by the wxODBC classes, and they still contain
-undefined data after a call to \helpref{wxDbTable::Query}{wxdbtablequery}. Only
+undefined data after a call to \helpref{wxDbTable::Query}{wxdbtablequery}. Only
after a successful call to one of the ::GetXxxx() functions is made do the
variables contain valid data.
It is not necessary to define column definitions for columns whose data is
-not going to be returned to the client. For example, if you want to query
+not going to be returned to the client. For example, if you want to query
the datasource for all users with a first name of 'GEORGE', but you only want
the list of last names associated with those rows (why return the FIRST\_NAME
column every time when you already know it is 'GEORGE'), you would only have
needed to define one column above.
You may have as many wxDbTable instances accessing the same table using the
-same wxDb instance as you desire. There is no limit imposed by the classes
-on this. All datasources supported (so far) also have no limitations on this.
-
+same wxDb instance as you desire. There is no limit imposed by the classes
+on this. All datasources supported (so far) also have no limitations on this.
{\bf Open the table}
-Opening the table technically is not doing anything with the datasource
-itself. Calling \helpref{wxDbTable::Open}{wxdbtableopen} simply does all the
-house keeping of checking that the specified table exists, that the current
+Opening the table is not technically doing anything with the datasource
+itself. Calling \helpref{wxDbTable::Open}{wxdbtableopen} simply does all the
+housekeeping of checking that the specified table exists, that the current
connected user has at least SELECT privileges for accessing the table,
-setting up the requisite cursors, binding columns and cursors, and
+setting up the requisite cursors, binding columns and cursors, and
constructing the default INSERT statement that is used when a new row is
inserted into the table (non-wxDB\_QUERY\_ONLY tables only).
}
\end{verbatim}
-The only reason that a call to \helpref{wxDbTable::Open}{wxdbtableopen} will likely fail is if the
-user has insufficient privileges to even SELECT the table. Other problems
+The only reason that a call to \helpref{wxDbTable::Open}{wxdbtableopen} is likely to fail is if the
+user has insufficient privileges to even SELECT the table. Other problems
could occur, such as being unable to bind columns, but these other reason
-point to some lack of resource (like memory). Any errors generated
+point to some lack of resource (like memory). Any errors generated
internally in the \helpref{wxDbTable::Open}{wxdbtableopen} function are logged to the error log
if SQL logging is turned on for the classes.
-
{\bf Use the table}
To use the table and the definitions that are now set up, we must first
Specifying a blank ORDERBY clause means that the datasource will return
the result set in whatever sequence it encounters rows which match the
-selection criteria. What this sequence is can be hard to determine.
+selection criteria. What this sequence is can be hard to determine.
Typically it depends on the index that the datasource used to find the
-rows which match the WHERE criteria. BEWARE - relying on the datasource
+rows which match the WHERE criteria. BEWARE - relying on the datasource
to return data in a certain sequence when you have not provided an ORDERBY
-clause will eventually cause a problem for your program. Databases can be
+clause will eventually cause a problem for your program. Databases can be
tuned to be COST-based, SPEED-based, or some other basis for how it gets
-your result set. In short, if you need your result set returned in a
+your result set. In short, if you need your result set returned in a
specific sequence, ask for it that way by providing an ORDERBY clause.
Using an ORDERBY clause can be a performance hit, as the database must
-sort the items before making the result set available to the client.
+sort the items before making the result set available to the client.
Creating efficient indexes that cause the data to be "found" in the correct
-ORDERBY sequence can be a big performance benefit. Also, in the large
+ORDERBY sequence can be a big performance benefit. Also, in the large
majority of cases, the database will be able to sort the records faster
than your application can read all the records in (unsorted) and then sort
-them. Let the database do the work for you!
+them. Let the database do the work for you!
Notice in the example above, a column that is not included in the bound
data columns ('AGE') will be used to sub-sort the result set.
The FROM clause in this example is blanked, as we are not going to be
-performing any table joins with this simple query. When the FROM clause
+performing any table joins with this simple query. When the FROM clause
is blank, it is assumed that all columns referenced are coming from
the default table for the wxDbTable instance.
\end{verbatim}
Typically, when an error occurs when calling \helpref{wxDbTable::Query}{wxdbtablequery}, it is a
-syntax problem in the WHERE clause that was specified. The exact SQL
-(datasource specific) reason for what caused the failure of \helpref{wxDbTable::Query}{wxdbtablequery}
+syntax problem in the WHERE clause that was specified. The exact SQL
+(datasource-specific) reason for what caused the failure of \helpref{wxDbTable::Query}{wxdbtablequery}
(and all other operations against the datasource can be found by
parsing the table's database connection's "errorList[]" array member for
the stored text of the error.
When the \helpref{wxDbTable::Query}{wxdbtablequery} returns TRUE, the
database was able to successfully complete the requested query using the
-provided criteria. This does not mean that there are any rows in the
+provided criteria. This does not mean that there are any rows in the
result set, it just mean that the query was successful.
\normalbox{IMPORTANT: The result created by the call to
-\helpref{wxDbTable::Query}{wxdbtablequery} can be one of two forms. It is
+\helpref{wxDbTable::Query}{wxdbtablequery} can take one of two forms. It is
either a snapshot of the data at the exact moment that the database
determined the record matched the search criteria, or it is a pointer to
-the row that matched the selection criteria. Which form of behavior is
-datasource dependent. If it is a snapshot, the data may have changed
+the row that matched the selection criteria. Which form of behavior is
+datasource dependent. If it is a snapshot, the data may have changed
since the result set was constructed, so beware if your datasource
-uses snapshots and call \helpref{wxDbTable::Refresh}{wxdbtablerefresh}. Most larger brand databases
+uses snapshots and call \helpref{wxDbTable::Refresh}{wxdbtablerefresh}. Most larger brand databases
do not use snapshots, but it is important to mention so that your application
-can handle it properly if your datasource does. }
+can handle it properly if your datasource does.}
To retrieve the data, one of the data fetching routines must be used to
request a row from the result set, and to store the data from the result
-set into the bound memory variables. After \helpref{wxDbTable::Query}{wxdbtablequery}
+set into the bound memory variables. After \helpref{wxDbTable::Query}{wxdbtablequery}
has completed successfully, the default/current cursor is placed so it
-is pointing just before the first record in the result set. If the
+is pointing just before the first record in the result set. If the
result set is empty (no rows matched the criteria), then any calls to
retrieve data from the result set will return FALSE.
\end{verbatim}
The sample code above will read the next record in the result set repeatedly
-until the end of the result set has been reached. The first time that
+until the end of the result set has been reached. The first time that
\helpref{wxDbTable::GetNext}{wxdbtablegetnext} is called right after the successful
call to \helpref{wxDbTable::Query}{wxdbtablequery}, it actually returns the first record
in the result set.
\helpref{wxDbTable::GetNext}{wxdbtablegetnext} (as well as all the other
wxDbTable::GetXxxxx() functions) will return FALSE.
-
{\bf Close the table}
When the program is done using a wxDbTable instance, it is as simple as
deleting the table pointer (or if declared statically, letting the
-variable go out of scope). Typically the default destructor will take
+variable go out of scope). Typically the default destructor will take
care of all that is required for cleaning up the wxDbTable instance.
\begin{verbatim}
table (but not the environment handle used by the datasource connection
that the wxDbTable instance was using).
-
-
{\bf Close the datasource connection}
After all tables that have been using a datasource connection have been
-closed (this can be checked by calling \helpref{wxDb::GetTableCount}{wxdbgettablecount}
+closed (this can be verified by calling \helpref{wxDb::GetTableCount}{wxdbgettablecount}
and checking that it returns 0), then you may close the datasource
-connection. The method of doing this is dependent on whether the
+connection. The method of doing this is dependent on whether the
non-caching or caching method was used to obtain the datasource connection.
If the datasource connection was created manually (non-cached), closing the
\end{verbatim}
Note that the above code just frees the connection so that it can be
-re-used on the next call the \helpref{wxDbGetConnection}{wxdbfunctions}. To actually dispose
+re-used on the next call the \helpref{wxDbGetConnection}{wxdbfunctions}. To actually dispose
of the connection, releasing all of its resources (other than the
environment handle), do the following:
wxDbCloseConnections();
\end{verbatim}
-
{\bf Release the ODBC environment handle}
Once all of the connections that used the ODBC environment handle (in
\normalbox{Remember to never release this environment handle if there are any
connections still using the handle.}
-
\subsection{wxODBC - Known Issues}\label{wxodbcknownissues}
As with creating wxWindows, writing the wxODBC classes was not the simple
-task of writing an application to run on a single type of computer system.
+task of writing an application to run on a single type of computer system.
The classes need to be cross-platform for different operating systems, and
they also needed to take in to account different database manufacturers and
-different ODBC driver manufacturers. Because of all the possible combinations
+different ODBC driver manufacturers. Because of all the possible combinations
of OS/database/drivers, it is impossible to say that these classes will work
-perfectly with datasource ABC, ODBC driver XYZ, on platform LMN. You may run
+perfectly with datasource ABC, ODBC driver XYZ, on platform LMN. You may run
in to some incompatibilities or unsupported features when moving your
-application from one environment to another. But that is what makes
-cross-platform programming fun. It is also pinpoints one of the great
-things about open source software. It can evolve!
+application from one environment to another. But that is what makes
+cross-platform programming fun. It is also pinpoints one of the great
+things about open source software. It can evolve!
The most common difference between different database/ODBC driver
manufacturers in regards to these wxODBC classes is the lack of
-standard error codes being returned to the calling program. Sometimes
+standard error codes being returned to the calling program. Sometimes
manufacturers have even changed the error codes between versions of
-their databases/drivers.
+their databases/drivers.
In all the tested databases, every effort has been made to determine
the correct error codes and handle them in the class members that need
to check for specific error codes (such as TABLE DOES NOT EXIST when
-you try to open a table that has not been created yet). Adding support
+you try to open a table that has not been created yet). Adding support
for additional databases in the future requires adding an entry for the
database in the \helpref{wxDb::Dbms}{wxdbdbms} function, and then handling any error codes
returned by the datasource that do not match the expected values.
-
{\bf Databases}
Following is a list of known issues and incompatibilities that the
-wxODBC classes have between different datasources. An up to date
+wxODBC classes have between different datasources. An up to date
listing of known issues can be seen in the comments of the source
for \helpref{wxDb::Dbms}{wxdbdbms}.
{\it DBASE}
-NOTE: dBase is not a true ODBC datasource. You only have access to as much
+NOTE: dBase is not a true ODBC datasource. You only have access to as much
functionality as the driver can emulate.
\begin{itemize}\itemsep=0pt
\item Does not support the SQL\_TIMESTAMP structure
\item Supports only one cursor and one connect (apparently? with Microsoft driver only?)
-\item Does not automatically create the primary index if the 'keyField' param of SetColDef is TRUE. The user must create ALL indexes from their program with calls to \helpref{wxDbTable::CreateIndex}{wxdbtablecreateindex}
+\item Does not automatically create the primary index if the 'keyField' param of SetColDef is TRUE. The user must create ALL indexes from their program with calls to \helpref{wxDbTable::CreateIndex}{wxdbtablecreateindex}
\item Table names can only be 8 characters long
\item Column names can only be 10 characters long
\item Currently cannot CREATE a dBase table - bug or limitation of the drivers used??
{\it SYBASE (all)}
\begin{itemize}\itemsep=0pt
\item To lock a record during QUERY functions, the reserved word 'HOLDLOCK' must be added after every table name involved in the query/join if that table's matching record(s) are to be locked
-\item Ignores the keywords 'FOR UPDATE'. Use the HOLDLOCK functionality described above
+\item Ignores the keywords 'FOR UPDATE'. Use the HOLDLOCK functionality described above
\end{itemize}
{\it SYBASE (Enterprise)}
{\it mySQL}
\begin{itemize}\itemsep=0pt
\item If a column is part of the Primary Key, the column cannot be NULL.
-\item Cannot support selecting for update [\helpref{wxDbTable::CanSelectForUpdate}{wxdbtablecanselectforupdate}]. Always returns FALSE.
-\item Columns that are part of primary or secondary keys must be defined as being NOT NULL when they are created. Some code is added in \helpref{wxDbTable::CreateIndex}{wxdbtablecreateindex} to try to adjust the column definition if it is not defined correctly, but it is experimental (as of wxWindows v2.2.1)
+\item Cannot support selecting for update [\helpref{wxDbTable::CanSelectForUpdate}{wxdbtablecanselectforupdate}]. Always returns FALSE.
+\item Columns that are part of primary or secondary keys must be defined as being NOT NULL when they are created. Some code is added in \helpref{wxDbTable::CreateIndex}{wxdbtablecreateindex} to try to adjust the column definition if it is not defined correctly, but it is experimental (as of wxWindows v2.2.1)
\item Does not support sub-queries in SQL statements
\end{itemize}
\item Columns which are part of a primary key must be declared as NOT NULL
\end{itemize}
-
{\bf UNICODE with wxODBC classes}
The ODBC classes support for Unicode is yet in early experimental stage and
hasn't been tested extensively. It might work for you or it might not: please
report the bugs/problems you have encountered in the latter case.
-\subsection{wxODBC - Sample Code #1}\label{wxodbcsamplecode1}
+\subsection{wxODBC - Sample Code {\tt\#}1}\label{wxodbcsamplecode1}
Simplest example of establishing/opening a connection to an ODBC datasource,
binding variables to the columns for read/write usage, opening an
!wxDB_QUERY_ONLY, "");
//
-// Bind the columns that you wish to retrieve. Note that there must be
+// Bind the columns that you wish to retrieve. Note that there must be
// 'numTableColumns' calls to SetColDefs(), to match the wxDbTable definition
//
// Not all columns need to be bound, only columns whose values are to be
\rtfsp\helpref{wxQueryField}{wxqueryfield}
\normalboxd{The more sophisticated wxODBC classes (wxDb/wxDbTable) are the
-recommended classes for doing database/ODBC work with wxWindows. These new
+recommended classes for doing database/ODBC work with wxWindows. These new
classes replace the wxWindows v1.6x classes wxDatabase.
Documentation for the old wxDatabase class and its associated classes is still
Use \helpref{wxDb}{wxdb} and \helpref{wxDbTable}{wxdbtable} instead.
-
Each wxRecordSet represents a database query. You can make multiple queries
at a time by using multiple wxRecordSets with a wxDatabase or you can make
your queries in sequential order using the same wxRecordSet.
Examples:
-\tt{SELECT * FROM Book}
+{\tt SELECT * FROM Book}
Selects all rows and columns from table Book.
-\tt{SELECT Title, RetailPriceAmount FROM Book WHERE RetailPriceAmount > 20.0}
+{\tt SELECT Title, RetailPriceAmount FROM Book WHERE RetailPriceAmount > 20.0}
Selects columns Title and RetailPriceAmount from table Book, returning only
the rows that match the WHERE clause.
-\tt{SELECT * FROM Book WHERE CatCode = 'LL' OR CatCode = 'RR'}
+{\tt SELECT * FROM Book WHERE CatCode = 'LL' OR CatCode = 'RR'}
Selects all columns from table Book, returning only
the rows that match the WHERE clause.
-\tt{SELECT * FROM Book WHERE CatCode IS NULL}
+{\tt SELECT * FROM Book WHERE CatCode IS NULL}
Selects all columns from table Book, returning only rows where the CatCode column
is NULL.
-\tt{SELECT * FROM Book ORDER BY Title}
+{\tt SELECT * FROM Book ORDER BY Title}
Selects all columns from table Book, ordering by Title, in ascending order. To specify
descending order, add DESC after the ORDER BY Title clause.
-\tt{SELECT Title FROM Book WHERE RetailPriceAmount >= 20.0 AND RetailPriceAmount <= 35.0}
+{\tt SELECT Title FROM Book WHERE RetailPriceAmount >= 20.0 AND RetailPriceAmount <= 35.0}
Selects records where RetailPriceAmount conforms to the WHERE expression.
Example:
-\tt{UPDATE Incident SET X = 123 WHERE ASSET = 'BD34'}
+{\tt UPDATE Incident SET X = 123 WHERE ASSET = 'BD34'}
This example sets a field in column `X' to the number 123, for the record
where the column ASSET has the value `BD34'.
-
-
projects / wxWidgets.git / blobdiff