QSqlDatabase Class

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# QSqlDatabase Class Reference
[sql module]

The QSqlDatabase class is used to create SQL database connections and provide transaction handling. More...

`#include <qsqldatabase.h>`

Inherits QObject.

List of all member functions.

## Public Members

- ~QSqlDatabase ()
- bool open ()
- bool open ( const QString & user, const QString & password )
- void close ()
- bool isOpen () const
- bool isOpenError () const
- QStringList tables () const
- QSqlIndex primaryIndex ( const QString & tablename ) const
- QSqlRecord record ( const QString & tablename ) const
- QSqlRecord record ( const QSqlQuery & query ) const
- QSqlRecordInfo recordInfo ( const QString & tablename ) const
- QSqlRecordInfo recordInfo ( const QSqlQuery & query ) const
- QSqlQuery exec ( const QString & query = QString::null ) const
- QSqlError lastError () const
- bool transaction ()
- bool commit ()
- bool rollback ()
- virtual void setDatabaseName ( const QString & name )
- virtual void setUserName ( const QString & name )
- virtual void setPassword ( const QString & password )
- virtual void setHostName ( const QString & host )
- virtual void setPort ( int p )
- QString databaseName () const
- QString userName () const
- QString password () const
- QString hostName () const
- QString driverName () const
- int port () const
- QSqlDriver * driver () const

## Static Public Members

- QSqlDatabase * addDatabase ( const QString & type, const QString & connectionName = defaultConnection )
- QSqlDatabase * database ( const QString & connectionName = defaultConnection, bool open = TRUE )
- void removeDatabase ( const QString & connectionName )
- bool contains ( const QString & connectionName = defaultConnection )
- QStringList drivers ()

## Properties

- QString databaseName - the name of the database
- QString hostName - the host name where the database resides
- QString password - the password used to connect to the database
- int port - the port used to connect to the database
- QString userName - the user name connected to the database

## Protected Members

- QSqlDatabase ( const QString & driver, const QString & name, QObject * parent = 0, const char * objname = 0 )

## 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 addDatabase(). 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 = QSqlDatabase::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

### QString databaseName

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().

### QString hostName

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().

### QString password

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().

### QString userName

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().

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