sql-driver.html

QT 下载资料仅供参考

qmake -o Makefile "INCLUDEPATH+=$ORACLE_HOME/rdbms/public $ORACLE_HOME/rdbms/demo" "LIBS+=-L$ORACLE_HOME/lib -lclntsh -lwtc9" oci.pro
make
</pre>
 
<p> <h4> How to build the plugin on Windows
</h4>
<a name="3-2-5"></a><p> Choosing the option "Programmer" in the Oracle Client Installer from
the Oracle Client Installation CD is sufficient to build the plugin.
<p> Build the plugin as follows (here it is assumed that Oracle Client is
installed in C:\oracle):
<p> <pre>
set INCLUDE=%INCLUDE%;c:\oracle\oci\include
set LIB=%LIB%;c:\oracle\oci\lib\msvc
cd %QTDIR%\plugins\src\sqldrivers\oci
qmake -o Makefile oci.pro
nmake
</pre>
 
<p> When you run your application you will also need to add the oci.dll
path to your PATH environment variable:
<p> <pre>
set PATH=%PATH%;c:\oracle\bin
</pre>
 
<p> If you are not using a Microsoft compiler, replace "nmake" with "make"
in the statement above.
<p> <a name="QODBC3"></a>
<h3> QODBC3 - Open Database Connectivity (ODBC)
</h3>
<a name="3-3"></a><p> <!-- index QODBC3 --><a name="QODBC3"></a>
<p> <h4> General information
</h4>
<a name="3-3-1"></a><p> ODBC is a general interface that allows you to connect to multiple
DBMS using a common interface. The QODBC3 driver allows you to connect
to an ODBC driver manager and access the available data sources. Note
that you also need to install and configure ODBC drivers for the ODBC
driver manager that is installed on your system. The QODBC3 plugin
then allows you to use these data sources in your Qt project.
<p> On Windows systems after 95 an ODBC driver manager should be installed
by default, for Unix systems there are some implementations which have to
be installed first. Note that every client that uses your application
is required to have an ODBC driver manager installed, otherwise the
QODBC3 plugin will not work.
<p> Be aware that when connecting to an ODBC datasource you must pass in
the name of the ODBC datasource to the <a href="qsqldatabase.html#setDatabaseName">QSqlDatabase::setDatabaseName</a>()
function - not the actual database name.
<p> The QODBC3 Plugin needs an ODBC compliant driver manager version 2.0 or
greater to work. Some ODBC drivers claim to be version 2.0 compliant,
but do not offer all needed functionality. The QODBC3 plugin therefore
checks whether the data source can be used after a connection has been
established and refuses to work if the check fails. If you don't
like this behaviour, you can remove the <tt>#define ODBC_CHECK_DRIVER</tt>
line from the file <tt>qsql_odbc.cpp</tt>. Do this at your own risk!
<p> Note that some DBMSs, like Microsoft Access, does not return the
primary index for a table through ODBC. You can still use the QODBC3
driver, but you will have to manage table indices yourself (through
<a href="qsqlcursor.html#setPrimaryIndex">QSqlCursor::setPrimaryIndex</a>()), otherwise INSERT, UPDATE and DELETE
operations will fail in data-aware Qt widgets. You will have to
comment out the <tt>#define ODBC_CHECK_DRIVER</tt> line and recompile the
driver, otherwise you will not be able to connect to a Microsoft
Access database.
<p> <h4> How to build the plugin on Unix/Linux
</h4>
<a name="3-3-2"></a><p> It is recommended that you use unixODBC. You can find the newest
version and ODBC drivers at <a href="http://www.unixodbc.org">http://www.unixodbc.org</a>.
You need the unixODBC header files and shared libraries.
<p> Tell qmake where to find the unixODBC header files and shared libraries
(here it is assumed that unixODBC is installed in /usr/local/unixODBC)
and run make:
<p> <pre>
cd $QTDIR/plugins/src/sqldrivers/odbc
qmake "INCLUDEPATH+=/usr/local/unixODBC/include" "LIBS+=-L/usr/local/unixODBC/lib -lodbc"
make
</pre>
 
<p> <h4> How to build the plugin on Windows
</h4>
<a name="3-3-3"></a><p> The ODBC header and include files should already be installed in the
right directories. You just have to build the plugin as follows:
<p> <pre>
cd %QTDIR%\plugins\src\sqldrivers\odbc
qmake -o Makefile odbc.pro
nmake
</pre>
 
<p> If you are not using a Microsoft compiler, replace "nmake" with "make" in the
statement above.
<p> <a name="QPSQL7"></a>
<h3> QPSQL7 - PostgreSQL version 6 and 7
</h3>
<a name="3-4"></a><p> <!-- index QPSQL7 --><a name="QPSQL7"></a>
<p> <h4> General information
</h4>
<a name="3-4-1"></a><p> The QPSQL7 driver supports both version 6 and 7 of PostgreSQL. We
recommend compiling the plugin with a recent version of the PostgreSQL
Client API (libpq) because it is more stable and still downward
compatible.
<p> If you want to link the plugin against the libpq shipped with version
6 we recomment a recent version like PostgreSQL 6.5.3, otherwise a
connection to a version 7 server may not work.
<p> The driver auto-detects the server version of PostgreSQL after a
connection was successful. If the server is too old or the version
information cannot be determined a warning is issued.
<p> For more information about PostgreSQL visit <a href="http://www.postgresql.org">http://www.postgresql.org</a>.
<p> <h4> Unicode support
</h4>
<a name="3-4-2"></a><p> The QPSQL7 driver automatically detects whether the PostgreSQL
database you are connecting to supports Unicode or not. Unicode is
automatically used if the server supports it. Note that the driver
only supports the UTF-8 encoding. If your database uses any other
encoding, the server has to be compiled with Unicode conversion
support.
<p> Unicode support was introduced in PostgreSQL version 7.1 and it will
only work if both the server and the client library have been compiled
with multibyte support. More information about how to set up a
multibyte enabled PostgreSQL server can be found in the PostgreSQL
Administrator Guide, Chapter 5.
<p> <h4> BLOB support
</h4>
<a name="3-4-3"></a><p> Binary Large Objects can be fetched but not inserted. Please use the
PostgreSQL command lo_import to insert binary data into the database.
<p> <h4> How to build the plugin on Unix/Linux
</h4>
<a name="3-4-4"></a><p> Just installing "libpq.so" and the corresponding header files is
unfortunately not sufficient. You have to get the whole source
distribution and run the configure script once (there is no need to
build it if you have already installed a binary distribution).
<p> Tell qmake where to find the PostgreSQL header files and shared
libraries (here it is assumed that you extracted the PostgreSQL source
code in /usr/src/psql and the shared library is installed in /usr/lib)
and run make:
<p> <pre>
cd $QTDIR/plugins/src/sqldrivers/psql
qmake -o Makefile "INCLUDEPATH+=/usr/src/psql/src/include /usr/src/psql/src/interfaces/libpq" "LIBS+=-L/usr/lib -lpq" psql.pro
make
</pre>
 
<p> <a name="QTDS7"></a>
<h3> QTDS7 - Sybase Adaptive Server and Microsoft SQL Server
</h3>
<a name="3-5"></a><p> <!-- index QTDS7 --><a name="QTDS7"></a>
<p> <h4> How to build the plugin on Unix/Linux
</h4>
<a name="3-5-1"></a><p> Under Unix, two libraries are available which support the TDS protocol:
<p> - FreeTDS, a free implementation of the TDS protocol ( <a href="http://www.freetds.org">http://www.freetds.org</a> ).
Note that FreeTDS is not yet stable, so some functionality may not work
as expected.
<p> - Sybase Open Client, available from <a href="http://www.sybase.com">http://www.sybase.com</a>
Note for Linux users: Get the Open Client RPM from <a href="http://linux.sybase.com">http://linux.sybase.com</a>
<p> Regardless of which library you use, the shared object file
"libsybdb.so" is needed. Set the SYBASE environment variable to point
to the directory where you installed the client library and execute
qmake:
<p> <pre>
cd $QTDIR/plugins/src/sqldrivers/tds
qmake -o Makefile "INCLUDEPATH=$SYBASE/include" "LIBS=-L$SYBASE/lib -lsybdb"
make
</pre>
 
<p> <h4> How to build the plugin on Windows
</h4>
<a name="3-5-2"></a><p> You can either use the DB-Library supplied by Microsoft or the Sybase Open Client
( <a href="http://www.sybase.com">http://www.sybase.com</a> ). You have to include NTWDBLIB.LIB
to build the plugin:
<p> <pre>
cd %QTDIR%\plugins\src\sqldrivers\tds
qmake -o Makefile "LIBS+=NTWDBLIB.LIB" tds.pro
nmake
</pre>
 
<p> By default the Microsoft library is used on Windows, if you want to force
the use of the Sybase Open Client, you have to define
Q_USE_SYBASE in %QTDIR%\src\sql\drivers\tds\qsql_tds.cpp.
<p> <a name="troubleshooting"></a>
<h2> Troubleshooting
</h2>
<a name="4"></a><p> You should always use client libraries that have been compiled with
the same compiler as you are using for your project. If you cannot get
a source distibution to compile the client libraries yourself, you
have to make sure that the pre-compiled library is compatible with
your compiler, otherwise you will get a lot of "undefined symbols"
errors. Some compilers have tools to convert libraries, e.g. Borland
ships the tool <tt>COFF2OMF.EXE</tt> to convert libraries that have been
generated with Microsoft Visual C++.
<p> If the compilation of a plugin succeeds but it cannot be loaded,
make sure that the following requirements are met:
<p> <ul>
<li> Make sure you are using a shared Qt library, you cannot use the
plugins with a static build.
<li> Make sure that the environment variable QTDIR points to the right
directory. Go to the $QTDIR/plugins/sqldrivers directory and make sure
that the plugin exists in that directory.
<li> Make sure that the client libraries of the DBMS are available on the 
system. On Unix, run the command <tt>ldd</tt> and pass the name of the
plugin as parameter, for example <tt>ldd libqsqlmysql.so</tt>. You will
get a warning if any of the client libraries couldn't be found. 
On Windows, you can use the dependency walker of Visual Studio.
</ul>
<p> <a name="development"></a>
<h2> How to write your own database driver
</h2>
<a name="5"></a><p> <a href="qsqldatabase.html">QSqlDatabase</a> is responsible for loading and managing database driver
plugins.  When a database is added (see <a href="qsqldatabase.html#addDatabase">QSqlDatabase::addDatabase</a>()),
the appropriate driver plugin is loaded (using <a href="qsqldriverplugin.html">QSqlDriverPlugin</a>).
QSqlDatabase relies on the driver plugin to provide interfaces for
<a href="qsqldriver.html">QSqlDriver</a> and <a href="qsqlresult.html">QSqlResult</a>.
<p> QSqlDriver is an abstract base class which defines the functionality
of a SQL database driver.  This includes functions such as
<a href="qsqldriver.html#open">QSqlDriver::open</a>() and <a href="qsqldriver.html#close">QSqlDriver::close</a>().  QSqlDriver is responsible
for connecting to a database, establish the proper environment, etc.
In addition, QSqlDriver can create <a href="qsqlquery.html">QSqlQuery</a> objects appropriate for
the particular database API.  QSqlDatabase forwards many of its
function calls directly to QSqlDriver which provides the concrete
implementation.
<p> QSqlResult is an abstract base class which defines the functionality
of a SQL database query.  This includes statements such as SELECT,
UPDATE, or ALTER TABLE.  QSqlResult contains functions such as
QSqlResult::next() and QSqlResult::value().  QSqlResult is responsible
for sending queries to the database, returning result data, etc.
QSqlQuery forwards many of its function calls directly to <a href="qsqlresult.html">QSqlResult</a>
which provides the concrete implementation.
<p> <a href="qsqldriver.html">QSqlDriver</a> and QSqlResult are closely connected.  When implementing a
Qt SQL driver, both of these classes must to be subclassed and the
abstract virtual methods in each class must be implemented.  
<p> To implement a Qt SQL driver as a plugin (so that it is recognized and
loaded by the Qt library at runtime), the driver must use the
Q_EXPORT_PLUGIN macro. Please read the <a href="plugins-howto.html">Qt
Plugin</a> documentation for more information on this. You can
also check out how this is done in the SQL plugins that is provided
with Qt in <tt>QTDIR/plugins/src/sqldrivers</tt> and <tt>QTDIR/src/sql/drivers</tt>.
<p> 
<!-- eof -->
<p><address><hr><div align=center>
<table width=100% cellspacing=0 border=0><tr>
<td>Copyright &copy; 2002 
<a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
<td align=right><div align=right>Qt version 3.0.5</div>
</table></div></address></body>
</html>