source: trunk/doc/src/sql-programming/sql-driver.qdoc@ 762

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/*!
    \page sql-driver.html
    \title SQL Database Drivers
    \brief How to configure and install QtSql drivers for supported databases.

    \ingroup best-practices

    The QtSql module uses driver \l{How to Create Qt
    Plugins}{plugins} to communicate with the different database
    APIs. Since Qt's SQL Module API is database-independent, all
    database-specific code is contained within these drivers. Several
    drivers are supplied with Qt and other drivers can be added. The
    driver source code is supplied and can be used as a model for
    \l{#development}{writing your own drivers}.

    \tableofcontents

    \section1 Supported Databases

    The table below lists the drivers included with Qt. Due to
    license incompatibilities with the GPL, not all of the plugins
    are provided with Open Source Versions of Qt.

    \table
    \header \o Driver name \o DBMS
    \row \o \link #QDB2 QDB2\endlink \o IBM DB2 (version 7.1 and above)
    \row \o \link #QIBASE QIBASE\endlink \o Borland InterBase
    \row \o \link #QMYSQL QMYSQL\endlink \o MySQL
    \row \o \link #QOCI QOCI\endlink \o Oracle Call Interface Driver
    \row \o \link #QODBC QODBC\endlink
         \o Open Database Connectivity (ODBC) - Microsoft SQL Server and other
            ODBC-compliant databases
    \row \o \link #QPSQL QPSQL\endlink \o PostgreSQL (versions 7.3 and above)
    \row \o \link #QSQLITE2 QSQLITE2\endlink \o SQLite version 2
    \row \o \link #QSQLITE QSQLITE\endlink \o SQLite version 3
    \row \o \link #QTDS QTDS\endlink \o Sybase Adaptive Server
    \endtable

    SQLite is the in-process database system with the best test coverage
    and support on all platforms. Oracle via OCI, and PostreSQL and MySQL
    through either ODBC or a native driver are well-tested on Windows and
    Linux. The completeness of the support for other systems depends on the
    availability and quality of client libraries.

    \bold{Note:} To build a driver plugin you need to have the appropriate
    client library for your Database Management System (DBMS). This provides
    access to the API exposed by the DBMS, and is typically shipped with it.
    Most installation programs also allow you to install "development
    libraries", and these are what you need. These libraries are responsible
    for the low-level communication with the DBMS.

    \target building
    \section1 Building the Drivers Using Configure

    On Unix and Mac OS X, the Qt \c configure script tries to
    automatically detect the available client libraries on your
    machine. Run \c{configure -help} to see what drivers can be
    built. You should get an output similar to this:

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 0

    The \c configure script cannot detect the neccessary libraries
    and include files if they are not in the standard paths, so it
    may be necessary to specify these paths using the \c -I and \c -L
    command-line options. For example, if your MySQL include files
    are installed in \c /usr/local/mysql (or in \c{C:\mysql\include}
    on Windows), then pass the following parameter to configure: \c
    -I/usr/local/mysql (or \c{-I C:\mysql\include} for Windows).

    On Windows the \c -I parameter doesn't accept spaces in
    filenames, so use the 8.3 name instead; for example, use
    \c{C:\progra~1\mysql} instead of \c{C:\Program Files\mysql}.

    Use the \c{-qt-sql-<driver>} parameter to build the database driver
    statically into your Qt library or \c{-plugin-sql-<driver>} to build
    the driver as a plugin. Look at the sections that follow for
    additional information about required libraries.

    \target buildingmanually
    \section1 Building the Plugins Manually

    \target QMYSQL
    \section2 QMYSQL for MySQL 4 and higher

    \section3 QMYSQL Stored Procedure Support

    MySQL 5 introduces stored procedure support at the SQL level, but no
    API to control IN, OUT and INOUT parameters. Therefore, parameters
    have to be set and read using SQL commands instead of QSqlQuery::bindValue().

    Example stored procedure:

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 1

    Source code to access the OUT values:

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 2

    \bold{Note:} \c{@outval1} and \c{@outval2} are variables local to the current
    connection and will not be affected by queries sent from another host
    or connection.

    \section3 Embedded MySQL Server

    The MySQL embedded server is a drop-in replacement for the normal
    client library. With the embedded MySQL server, a MySQL server is
    not required to use MySQL functionality.

    To use the embedded MySQL server, simply link the Qt plugin to \c
    libmysqld instead of libmysqlclient. This can be done by replacing
    \c -lmysqlclient_r by \c -lmysqld in the \c qmake command in the
    section below.

    Please refer to the MySQL documentation, chapter "libmysqld, the Embedded
    MySQL Server Library" for more information about the MySQL embedded server.

    \section3 How to Build the QMYSQL Plugin on Unix and Mac OS X

    You need the MySQL header files and as well as the shared library
    \c{libmysqlclient.so}. Depending on your Linux distribution you may
    need to install a package which is usually called "mysql-devel".

    Tell \l qmake where to find the MySQL header files and shared
    libraries (here it is assumed that MySQL is installed in
    \c{/usr/local}) and run \c{make}:

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 3

    After installing Qt, as described in the \l{Installing Qt on X11
    Platforms} document, you also need to install the plugin in the
    standard location:

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 4

    \section3 How to Build the QMYSQL Plugin on Windows

    You need to get the MySQL installation files. Run \c SETUP.EXE and
    choose "Custom Install". Install the "Libs & Include Files" Module.
    Build the plugin as follows (here it is assumed that MySQL is
    installed in \c{C:\MySQL}):

    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 5

    If you are not using a Microsoft compiler, replace \c nmake with \c
    make in the line above.

    \note This database plugin is not supported for Windows CE.

    \note Including \c{"-o Makefile"} as an argument to \l qmake to
    tell it where to build the makefile can cause the plugin to be
    built in release mode only. If you are expecting a debug version
    to be built as well, don't use the \c{"-o Makefile"} option.

    \target QOCI
    \section2 QOCI for the Oracle Call Interface (OCI)

    \section3 General Information about the OCI plugin

    The Qt OCI plugin supports Oracle 9i, 10g and higher. After
    connecting to the Oracle server, the plugin will auto-detect the
    database version and enable features accordingly.

    It's possible to connect to a Oracle database without a tnsnames.ora file.
    This requires that the database SID is passed to the driver as the database
    name and that a hostname is given.

    \section3 OCI User Authentication

    The Qt OCI plugin supports authentication using
    external credentials (OCI_CRED_EXT). Usually, this means that the database
    server will use the user authentication provided by the operating system
    instead of its own authentication mechanism.

    Leave the username and password empty when opening a connection with
    QSqlDatabase to use the external credentials authentication.

    \section3 OCI BLOB/LOB Support

    Binary Large Objects (BLOBs) can be read and written, but be aware
    that this process may require a lot of memory. You should use a forward
    only query to select LOB fields (see QSqlQuery::setForwardOnly()).

    Inserting BLOBs should be done using either a prepared query where the
    BLOBs are bound to placeholders or QSqlTableModel, which uses a prepared
    query to do this internally.

    \section3 How to Build the OCI Plugin on Unix and Mac OS X

    For Oracle 10g, all you need is the "Instant Client Package - Basic" and
    "Instant Client Package - SDK". For Oracle prior to 10g, you require
    the standard Oracle client and the SDK packages.

    Oracle library files required to build the driver:

    \list
    \i \c libclntsh.so (all versions)
    \i \c libwtc9.so (only Oracle 9)
    \endlist

    Tell \c qmake where to find the Oracle header files and shared
    libraries and run make:

    For Oracle version 9:
    \snippet doc/src/snippets/code/doc_src_sql-driver.qdoc 6