The QSqlDatabase class is used to create SQL database
connections and provide transaction handling.
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Detailed Description
The QSqlDatabase class is used to create SQL database
connections and provide transaction handling.
This class is used to create connections to SQL databases. It also
provides transaction handling functions for those database drivers
that support transactions.
The QSqlDatabase class itself provides an abstract interface for
accessing many types of database backend. Database-specific drivers
are used internally to actually access and manipulate data, (see
QSqlDriver). Result set objects provide the interface for executing
and manipulating SQL queries (see QSqlQuery).
See also Database Classes.
Member Function Documentation
QSqlDatabase::QSqlDatabase ( const QString & driver, const QString & name, QObject * parent = 0, const char * objname = 0 ) [protected]
Creates a QSqlDatabase connection called name that uses the
driver referred to by driver, with the parent parent and the
object name objname. If the driver is not recognized, the
database connection will have no functionality.
The currently available drivers are:
- QODBC3 - ODBC (Open Database Connectivity) Driver
- QOCI8 - Oracle Call Interface Driver
- QPSQL7 - PostgreSQL v6.x and v7.x Driver
- QTDS7 - Sybase Adaptive Server and Microsoft SQL Server Driver
- QMYSQL3 - MySQL Driver
Note that additional 3rd party drivers can be loaded
dynamically.
QSqlDatabase::~QSqlDatabase ()
Destroys the object and frees any allocated resources.
QSqlDatabase * QSqlDatabase::addDatabase ( const QString & type, const QString & connectionName = defaultConnection ) [static]
Adds a database to the list of database connections using the
driver type and the connection name connectionName.
The database connection is referred to by connectionName. The
newly added database connection is returned. This pointer is owned
by QSqlDatabase and will be deleted on program exit or when
removeDatabase() is called. If connectionName is not specified,
the newly added database connection becomes the default database
connection for the application, and subsequent calls to database()
(without a database name parameter) will return a pointer to it.
See also database() and removeDatabase().
Examples: sql/overview/connect1/main.cpp, sql/overview/connection.cpp and sql/sqltable/main.cpp.
void QSqlDatabase::close ()
Closes the database connection, freeing any resources acquired.
bool QSqlDatabase::commit ()
Commits a transaction to the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature() and rollback().
bool QSqlDatabase::contains ( const QString & connectionName = defaultConnection ) [static]
Returns TRUE if the list of database connections contains connectionName; otherwise returns FALSE.
QSqlDatabase * QSqlDatabase::database ( const QString & connectionName = defaultConnection, bool open = TRUE ) [static]
Returns the database connection called connectionName. The
database connection must have been previously added with
database(). If open is TRUE (the default) and the database
connection is not already open it is opened now. If no connectionName is specified the default connection is used. If connectionName does not exist in the list of databases, 0 is
returned. The pointer returned is owned by QSqlDatabase and should
not be deleted.
Examples: sql/overview/basicbrowsing/main.cpp and sql/overview/create_connections/main.cpp.
QString QSqlDatabase::databaseName () const
Returns the name of the database.
See the "databaseName" property for details.
QSqlDriver * QSqlDatabase::driver () const
Returns the database driver used to access the database
connection.
QString QSqlDatabase::driverName () const
Returns the name of the driver used by the database connection.
QStringList QSqlDatabase::drivers () [static]
Returns a list of all available database drivers.
Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
QStringList list = myDatabase.drivers();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
QSqlQuery QSqlDatabase::exec ( const QString & query = QString::null ) const
Executes a SQL statement (e.g. an INSERT, UPDATE or DELETE
statement) on the database, and returns a QSqlQuery object. Use
lastError() to retrieve error information. If query is
QString::null, an empty, invalid query is returned and lastError()
is not affected.
See also QSqlQuery and lastError().
QString QSqlDatabase::hostName () const
Returns the host name where the database resides.
See the "hostName" property for details.
bool QSqlDatabase::isOpen () const
Returns TRUE if the database connection is currently open;
otherwise returns FALSE.
bool QSqlDatabase::isOpenError () const
Returns TRUE if there was an error opening the database
connection; otherwise returns FALSE. Error information can be
retrieved using the lastError() function.
QSqlError QSqlDatabase::lastError () const
Returns information about the last error that occurred on the
database. See QSqlError for more information.
Examples: sql/overview/connection.cpp and sql/sqltable/main.cpp.
bool QSqlDatabase::open ()
Opens the database connection using the current connection values.
Returns TRUE on success; otherwise returns FALSE. Error
information can be retrieved using the lastError() function.
See also lastError().
Examples: sql/overview/connect1/main.cpp, sql/overview/connection.cpp and sql/sqltable/main.cpp.
bool QSqlDatabase::open ( const QString & user, const QString & password )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Opens the database connection using user name and password.
Returns TRUE on success; otherwise returns FALSE. Error
information can be retrieved using the lastError() function.
See also lastError().
QString QSqlDatabase::password () const
Returns the password used to connect to the database.
See the "password" property for details.
int QSqlDatabase::port () const
Returns the port used to connect to the database.
See the "port" property for details.
QSqlIndex QSqlDatabase::primaryIndex ( const QString & tablename ) const
Returns the primary index for table tablename. If no primary
index exists an empty QSqlIndex will be returned.
QSqlRecord QSqlDatabase::record ( const QString & tablename ) const
Returns a QSqlRecord populated with the names of all the fields in
the table (or view) named tablename. The order in which the
fields are returned is undefined. If no such table (or view)
exists, an empty record is returned.
See also recordInfo().
QSqlRecord QSqlDatabase::record ( const QSqlQuery & query ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns a QSqlRecord populated with the names of all the fields
used in the SQL query. If the query is a "SELECT *" the order
in which fields are returned is undefined.
See also recordInfo().
QSqlRecordInfo QSqlDatabase::recordInfo ( const QString & tablename ) const
Returns a QSqlRecordInfo populated with meta data about the table
or view tablename. If no such table or view exists, an empty
record is returned.
See also QSqlRecordInfo, QSqlFieldInfo and record().
QSqlRecordInfo QSqlDatabase::recordInfo ( const QSqlQuery & query ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns a QSqlRecordInfo object with meta data for the QSqlQuery
query. Note that this overloaded function may return less
information than the recordInfo() function which takes the name of
a table as parameter.
See also QSqlRecordInfo, QSqlFieldInfo and record().
void QSqlDatabase::removeDatabase ( const QString & connectionName ) [static]
Removes the database connection connectionName from the list of
database connections.
Warning: There should be no open queries on the database
connection when this function is called, otherwise a resource leak
will occur.
bool QSqlDatabase::rollback ()
Rolls a transaction back on the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature(), commit() and transaction().
void QSqlDatabase::setDatabaseName ( const QString & name ) [virtual]
Sets the name of the database to name.
See the "databaseName" property for details.
void QSqlDatabase::setHostName ( const QString & host ) [virtual]
Sets the host name where the database resides to host.
See the "hostName" property for details.
void QSqlDatabase::setPassword ( const QString & password ) [virtual]
Sets the password used to connect to the database to password.
See the "password" property for details.
void QSqlDatabase::setPort ( int p ) [virtual]
Sets the port used to connect to the database to p.
See the "port" property for details.
void QSqlDatabase::setUserName ( const QString & name ) [virtual]
Sets the user name connected to the database to name.
See the "userName" property for details.
QStringList QSqlDatabase::tables () const
Returns a list of tables in the database.
Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
QStringList list = myDatabase.tables();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
bool QSqlDatabase::transaction ()
Begins a transaction on the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature(), commit() and rollback().
QString QSqlDatabase::userName () const
Returns the user name connected to the database.
See the "userName" property for details.
Property Documentation
This property holds the name of the database.
Note that the database name is the TNS Service Name for the QOCI8
(Oracle) driver, and the DSN or DSN filename for the QODBC3
driver. If a DSN filename is used, the file have to have a .dsn
extension.
There is no default value.
Set this property's value with setDatabaseName() and get this property's value with databaseName().
This property holds the host name where the database resides.
There is no default value.
Set this property's value with setHostName() and get this property's value with hostName().
This property holds the password used to connect to the database.
There is no default value.
Set this property's value with setPassword() and get this property's value with password().
int port
This property holds the port used to connect to the database.
There is no default value.
Set this property's value with setPort() and get this property's value with port().
This property holds the user name connected to the database.
There is no default value.
Set this property's value with setUserName() and get this property's value with userName().
This file is part of the Qt toolkit.
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