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# QSqlDriver Class Reference
[sql module]

The QSqlDriver class is an abstract base class for accessing SQL databases. More...

`#include <qsqldriver.h>`

Inherits QObject.

List of all member functions.

## Public Members

- enum DriverFeature { Transactions, QuerySize, BLOB, Unicode, PreparedQueries, NamedPlaceholders, PositionalPlaceholders }
- QSqlDriver ( QObject * parent = 0, const char * name = 0 )
- ~QSqlDriver ()
- bool isOpen () const
- bool isOpenError () const
- virtual bool beginTransaction ()
- virtual bool commitTransaction ()
- virtual bool rollbackTransaction ()
- virtual QStringList tables ( const QString & tableType ) const
- virtual QSqlIndex primaryIndex ( const QString & tableName ) const
- virtual QSqlRecord record ( const QString & tableName ) const
- virtual QSqlRecord record ( const QSqlQuery & query ) const
- virtual QSqlRecordInfo recordInfo ( const QString & tablename ) const
- virtual QSqlRecordInfo recordInfo ( const QSqlQuery & query ) const
- virtual QString nullText () const
- virtual QString formatValue ( const QSqlField * field, bool trimStrings = FALSE ) const
- QSqlError lastError () const
- virtual bool hasFeature ( DriverFeature f ) const = 0
- virtual bool open ( const QString & db, const QString & user = QString::null, const QString & password = QString::null, const QString & host = QString::null, int port = -1 ) = 0
- virtual void close () = 0
- virtual QSqlQuery createQuery () const = 0
- bool open ( const QString & db, const QString & user, const QString & password, const QString & host, int port, const QString & connOpts )

## Protected Members

- virtual void setOpen ( bool o )
- virtual void setOpenError ( bool e )
- virtual void setLastError ( const QSqlError & e )

## Detailed Description

The QSqlDriver class is an abstract base class for accessing SQL databases.

This class should not be used directly. Use QSqlDatabase instead.

See also Database Classes.

## Member Type Documentation

### QSqlDriver::DriverFeature

This enum contains a list of features a driver may support. Use hasFeature() to query whether a feature is supported or not.

- `QSqlDriver::Transactions` - whether the driver supports SQL transactions
- `QSqlDriver::QuerySize` - whether the database is capable of reporting the size of a query. Note that some databases do not support returning the size (i.e. number of rows returned) of a query, in which case QSqlQuery::size() will return -1
- `QSqlDriver::BLOB` - whether the driver supports Binary Large Object fields
- `QSqlDriver::Unicode` - whether the driver supports Unicode strings if the database server does
- `QSqlDriver::PreparedQueries` - whether the driver supports prepared query execution
- `QSqlDriver::NamedPlaceholders` - whether the driver supports usage of named placeholders
- `QSqlDriver::PositionalPlaceholders` - whether the driver supports usage of positional placeholders

More information about supported features can be found in the Qt SQL driver documentation.

See also hasFeature().

## Member Function Documentation

### QSqlDriver::QSqlDriver ( QObject * parent = 0, const char * name = 0 )

Default constructor. Creates a new driver with parent parent, called name.

### QSqlDriver::~QSqlDriver ()

Destroys the object and frees any allocated resources.

### bool QSqlDriver::beginTransaction ()`[virtual]`

Protected function which derived classes can reimplement to begin a transaction. If successful, return TRUE, otherwise return FALSE. The default implementation returns FALSE.

See also commitTransaction() and rollbackTransaction().

### void QSqlDriver::close ()`[pure virtual]`

Derived classes must reimplement this abstract virtual function in order to close the database connection. Return TRUE on success, FALSE on failure.

See also setOpen().

### bool QSqlDriver::commitTransaction ()`[virtual]`

Protected function which derived classes can reimplement to commit a transaction. If successful, return TRUE, otherwise return FALSE. The default implementation returns FALSE.

See also beginTransaction() and rollbackTransaction().

### QSqlQuery QSqlDriver::createQuery () const`[pure virtual]`

Creates an empty SQL result on the database. Derived classes must reimplement this function and return a QSqlQuery object appropriate for their database to the caller.

### QString QSqlDriver::formatValue ( const QSqlField * field, bool trimStrings = FALSE ) const`[virtual]`

Returns a string representation of the field value for the database. This is used, for example, when constructing INSERT and UPDATE statements.

The default implementation returns the value formatted as a string according to the following rules:

- If field is NULL, nullText() is returned.

- If field is character data, the value is returned enclosed in single quotation marks, which is appropriate for many SQL databases. Any embedded single-quote characters are escaped (replaced with two single-quote characters). If trimStrings is TRUE (the default is FALSE), all trailing whitespace is trimmed from the field.

- If field is date/time data, the value is formatted in ISO format and enclosed in single quotation marks. If the date/time data is invalid, nullText() is returned.

- If field is bytearray data, and the driver can edit binary fields, the value is formatted as a hexadecimal string.

- For any other field type toString() will be called on its value and the result returned.

See also QVariant::toString().

### bool QSqlDriver::hasFeature ( DriverFeature f ) const`[pure virtual]`

Returns TRUE if the driver supports feature f; otherwise returns FALSE.

Note that some databases need to be open() before this can be determined.

See also DriverFeature.

### bool QSqlDriver::isOpen () const

Returns TRUE if the database connection is open; otherwise returns FALSE.

### bool QSqlDriver::isOpenError () const

Returns TRUE if the there was an error opening the database connection; otherwise returns FALSE.

### QSqlError QSqlDriver::lastError () const

Returns a QSqlError object which contains information about the last error that occurred on the database.

### QString QSqlDriver::nullText () const`[virtual]`

Returns a string representation of the NULL value for the database. This is used, for example, when constructing INSERT and UPDATE statements. The default implementation returns the string "NULL".

### bool QSqlDriver::open ( const QString & db, const QString & user = QString::null, const QString & password = QString::null, const QString & host = QString::null, int port = -1 )`[pure virtual]`

Derived classes must reimplement this abstract virtual function in order to open a database connection on database db, using user name user, password password, host host and port port.

The function must return TRUE on success and FALSE on failure.

See also setOpen().

### bool QSqlDriver::open ( const QString & db, const QString & user, const QString & password, const QString & host, int port, const QString & connOpts )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Open a database connection on database db, using user name user, password password, host host, port port and connection options connOpts.

Returns TRUE on success and FALSE on failure.

See also setOpen().

### QSqlIndex QSqlDriver::primaryIndex ( const QString & tableName ) const`[virtual]`

Returns the primary index for table tableName. Returns an empty QSqlIndex if the table doesn't have a primary index. The default implementation returns an empty index.

### QSqlRecord QSqlDriver::record ( const QString & tableName ) const`[virtual]`

Returns a QSqlRecord populated with the names of the fields in table tableName. If no such table exists, an empty record is returned. The default implementation returns an empty record.

### QSqlRecord QSqlDriver::record ( const QSqlQuery & query ) const`[virtual]`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Returns a QSqlRecord populated with the names of the fields in the SQL query. The default implementation returns an empty record.

### QSqlRecordInfo QSqlDriver::recordInfo ( const QString & tablename ) const`[virtual]`

Returns a QSqlRecordInfo object with meta data about the table tablename.

### QSqlRecordInfo QSqlDriver::recordInfo ( const QSqlQuery & query ) const`[virtual]`

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.

### bool QSqlDriver::rollbackTransaction ()`[virtual]`

Protected function which derived classes can reimplement to rollback a transaction. If successful, return TRUE, otherwise return FALSE. The default implementation returns FALSE.

See also beginTransaction() and commitTransaction().

### void QSqlDriver::setLastError ( const QSqlError & e )`[virtual protected]`

Protected function which allows derived classes to set the value of the last error, e, that occurred on the database.

See also lastError().

### void QSqlDriver::setOpen ( bool o )`[virtual protected]`

Protected function which sets the open state of the database to o. Derived classes can use this function to report the status of open().

See also open() and setOpenError().

### void QSqlDriver::setOpenError ( bool e )`[virtual protected]`

Protected function which sets the open error state of the database to e. Derived classes can use this function to report the status of open(). Note that if e is TRUE the open state of the database is set to closed (i.e. isOpen() returns FALSE).

See also open().

### QStringList QSqlDriver::tables ( const QString & tableType ) const`[virtual]`

Returns a list of tables in the database. The default implementation returns an empty list.

The tableType argument describes what types of tables should be returned. Due to binary compatibility, the string contains the value of the enum QSql::TableTypes as text. An empty string should be treated as QSql::Tables for downward compatibility.

See also QSql::TableType.

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