QSqlDriver Class ReferenceThe QSqlDriver class is an abstract base class for accessing specific SQL databases. Далее... #include <QSqlDriver> Унаследован от: QObject. Открытые типы
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Подробное описаниеThe QSqlDriver class is an abstract base class for accessing specific SQL databases. This class should not be used directly. Use QSqlDatabase instead. If you want to create your own SQL drivers, you can subclass this class and reimplement its pure virtual functions and those virtual functions that you need. See How to Write Your Own Database Driver for more information. See also QSqlDatabase and QSqlResult. Описание типов-членовenum QSqlDriver::DriverFeatureThis enum contains a list of features a driver might support. Use hasFeature() to query whether a feature is supported or not.
More information about supported features can be found in the Qt SQL driver documentation. Смотрите также hasFeature(). enum QSqlDriver::IdentifierTypeThis enum contains a list of SQL identifier types.
enum QSqlDriver::StatementTypeThis enum contains a list of SQL statement (or clause) types the driver can create.
See also sqlStatement(). Описание функций-членовQSqlDriver::QSqlDriver ( QObject * parent = 0 )Constructs a new driver with the given parent. QSqlDriver::~QSqlDriver ()Удаляет объект и освобождает все выделенные ему ресурсы. bool QSqlDriver::beginTransaction () [virtual]This function is called to begin a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false. See also commitTransaction() and rollbackTransaction(). void QSqlDriver::close () [pure virtual]Derived classes must reimplement this pure virtual function in order to close the database connection. Return true on success, false on failure. See also open() and setOpen(). bool QSqlDriver::commitTransaction () [virtual]This function is called to commit a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false. See also beginTransaction() and rollbackTransaction(). QSqlResult * QSqlDriver::createResult () const [pure virtual]Creates an empty SQL result on the database. Derived classes must reimplement this function and return a QSqlResult object appropriate for their database to the caller. QString QSqlDriver::escapeIdentifier ( const QString & identifier, IdentifierType type ) const [virtual]Returns the identifier escaped according to the database rules. identifier can either be a table name or field name, dependent on type. Реализация по умолчанию ничего не делает. See also isIdentifierEscaped(). 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:
See also QVariant::toString(). QVariant QSqlDriver::handle () const [virtual]Returns the low-level database handle wrapped in a QVariant or an invalid variant if there is no handle. Warning: Use this with uttermost care and only if you know what you're doing. Warning: The handle returned here can become a stale pointer if the connection is modified (for example, if you close the connection). Warning: The handle can be NULL if the connection is not open yet. The handle returned here is database-dependent, you should query the type name of the variant before accessing it. This example retrieves the handle for a connection to sqlite: QSqlDatabase db = ...; QVariant v = db.driver()->handle(); if (v.isValid() && qstrcmp(v.typeName(), "sqlite3*")==0) { // v.data() returns a pointer to the handle sqlite3 *handle = *static_cast<sqlite3 **>(v.data()); if (handle != 0) { // check that it is not NULL ... } } This snippet returns the handle for PostgreSQL or MySQL: if (v.typeName() == "PGconn*") { PGconn *handle = *static_cast<PGconn **>(v.data()); if (handle != 0) ... } if (v.typeName() == "MYSQL*") { MYSQL *handle = *static_cast<MYSQL **>(v.data()); if (handle != 0) ... } See also QSqlResult::handle(). bool QSqlDriver::hasFeature ( DriverFeature feature ) const [pure virtual]Returns true if the driver supports feature feature; otherwise returns false. Note that some databases need to be open() before this can be determined. See also DriverFeature. bool QSqlDriver::isIdentifierEscaped ( const QString & identifier, IdentifierType type ) constReturns whether identifier is escaped according to the database rules. identifier can either be a table name or field name, dependent on type. Warning: Because of binary compatibility constraints, this function is not virtual. If you want to provide your own implementation in your QSqlDriver subclass, reimplement the isIdentifierEscapedImplementation() slot in your subclass instead. The isIdentifierEscapedFunction() will dynamically detect the slot and call it. See also stripDelimiters() and escapeIdentifier(). bool QSqlDriver::isIdentifierEscapedImplementation ( const QString & identifier, IdentifierType type ) const [protected slot]This slot returns whether identifier is escaped according to the database rules. identifier can either be a table name or field name, dependent on type. Because of binary compatibility constraints, isIdentifierEscaped() function (introduced in Qt 4.5) is not virtual. Instead, isIdentifierEscaped() will dynamically detect and call this slot. The default implementation assumes the escape/delimiter character is a double quote. Reimplement this slot in your own QSqlDriver if your database engine uses a different delimiter character. Эта функция была введена в Qt 4.6. See also isIdentifierEscaped(). bool QSqlDriver::isOpen () const [virtual]Returns true if the database connection is open; otherwise returns false. bool QSqlDriver::isOpenError () constReturns true if the there was an error opening the database connection; otherwise returns false. QSqlError QSqlDriver::lastError () constReturns a QSqlError object which contains information about the last error that occurred on the database. See also setLastError(). void QSqlDriver::notification ( const QString & name ) [signal]This signal is emitted when the database posts an event notification that the driver subscribes to. name identifies the event notification. Эта функция была введена в Qt 4.4. See also subscribeToNotification(). QSql::NumericalPrecisionPolicy QSqlDriver::numericalPrecisionPolicy () constВозвращает текущую политику точности по умолчанию для соединения с базой данных. Эта функция была введена в Qt 4.6. Смотрите также QSql::NumericalPrecisionPolicy, setNumericalPrecisionPolicy(), QSqlQuery::numericalPrecisionPolicy() и QSqlQuery::setNumericalPrecisionPolicy(). bool QSqlDriver::open ( const QString & db, const QString & user = QString(), const QString & password = QString(), const QString & host = QString(), int port = -1, const QString & options = QString() ) [pure virtual]Derived classes must reimplement this pure virtual function to open a database connection on database db, using user name user, password password, host host, port port and connection options options. The function must return 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. bool QSqlDriver::rollbackTransaction () [virtual]This function is called to rollback a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false. See also beginTransaction() and commitTransaction(). void QSqlDriver::setLastError ( const QSqlError & error ) [virtual protected]This function is used to set the value of the last error, error, that occurred on the database. Смотрите также lastError(). void QSqlDriver::setNumericalPrecisionPolicy ( QSql::NumericalPrecisionPolicy precisionPolicy )Sets the default numerical precision policy used by queries created by this driver to precisionPolicy. Замачание: Установка политики точности по умолчанию равной precisionPolicy не влияет на активные в данный момент запросы. Эта функция была введена в Qt 4.6. Смотрите также QSql::NumericalPrecisionPolicy, numericalPrecisionPolicy(), QSqlQuery::setNumericalPrecisionPolicy() и QSqlQuery::numericalPrecisionPolicy(). void QSqlDriver::setOpen ( bool open ) [virtual protected]This function sets the open state of the database to open. Derived classes can use this function to report the status of open(). See also open() and setOpenError(). void QSqlDriver::setOpenError ( bool error ) [virtual protected]This function sets the open error state of the database to error. Derived classes can use this function to report the status of open(). Note that if error is true the open state of the database is set to closed (i.e., isOpen() returns false). See also isOpenError(), open(), and setOpen(). QString QSqlDriver::sqlStatement ( StatementType type, const QString & tableName, const QSqlRecord & rec, bool preparedStatement ) const [virtual]Returns a SQL statement of type type for the table tableName with the values from rec. If preparedStatement is true, the string will contain placeholders instead of values. This method can be used to manipulate tables without having to worry about database-dependent SQL dialects. For non-prepared statements, the values will be properly escaped. QString QSqlDriver::stripDelimiters ( const QString & identifier, IdentifierType type ) constReturns the identifier with the leading and trailing delimiters removed, identifier can either be a table name or field name, dependent on type. If identifier does not have leading and trailing delimiter characters, identifier is returned without modification. Warning: Because of binary compatibility constraints, this function is not virtual, If you want to provide your own implementation in your QSqlDriver subclass, reimplement the stripDelimitersImplementation() slot in your subclass instead. The stripDelimiters() function will dynamically detect the slot and call it. Эта функция была введена в Qt 4.5. See also isIdentifierEscaped(). QString QSqlDriver::stripDelimitersImplementation ( const QString & identifier, IdentifierType type ) const [protected slot]This slot returns identifier with the leading and trailing delimiters removed, identifier can either be a tablename or field name, dependent on type. If identifier does not have leading and trailing delimiter characters, identifier is returned without modification. Because of binary compatibility constraints, the stripDelimiters() function (introduced in Qt 4.5) is not virtual. Instead, stripDelimiters() will dynamically detect and call this slot. It generally unnecessary to reimplement this slot. Эта функция была введена в Qt 4.6. See also stripDelimiters(). bool QSqlDriver::subscribeToNotification ( const QString & name )This function is called to subscribe to event notifications from the database. name identifies the event notification. If successful, return true, otherwise return false. The database must be open when this function is called. When the database is closed by calling close() all subscribed event notifications are automatically unsubscribed. Note that calling open() on an already open database may implicitly cause close() to be called, which will cause the driver to unsubscribe from all event notifications. When an event notification identified by name is posted by the database the notification() signal is emitted. Warning: Because of binary compatibility constraints, this function is not virtual. If you want to provide event notification support in your own QSqlDriver subclass, reimplement the subscribeToNotificationImplementation() slot in your subclass instead. The subscribeToNotification() function will dynamically detect the slot and call it. Эта функция была введена в Qt 4.4. See also unsubscribeFromNotification(), subscribedToNotifications(), and QSqlDriver::hasFeature(). bool QSqlDriver::subscribeToNotificationImplementation ( const QString & name ) [protected slot]This slot is called to subscribe to event notifications from the database. name identifies the event notification. If successful, return true, otherwise return false. The database must be open when this slot is called. When the database is closed by calling close() all subscribed event notifications are automatically unsubscribed. Note that calling open() on an already open database may implicitly cause close() to be called, which will cause the driver to unsubscribe from all event notifications. When an event notification identified by name is posted by the database the notification() signal is emitted. Reimplement this slot to provide your own QSqlDriver subclass with event notification support; because of binary compatibility constraints, the subscribeToNotification() function (introduced in Qt 4.4) is not virtual. Instead, subscribeToNotification() will dynamically detect and call this slot. The default implementation does nothing and returns false. Эта функция была введена в Qt 4.4. See also subscribeToNotification(). QStringList QSqlDriver::subscribedToNotifications () constReturns a list of the names of the event notifications that are currently subscribed to. Warning: Because of binary compatibility constraints, this function is not virtual. If you want to provide event notification support in your own QSqlDriver subclass, reimplement the subscribedToNotificationsImplementation() slot in your subclass instead. The subscribedToNotifications() function will dynamically detect the slot and call it. Эта функция была введена в Qt 4.4. See also subscribeToNotification() and unsubscribeFromNotification(). QStringList QSqlDriver::subscribedToNotificationsImplementation () const [protected slot]Returns a list of the names of the event notifications that are currently subscribed to. Reimplement this slot to provide your own QSqlDriver subclass with event notification support; because of binary compatibility constraints, the subscribedToNotifications() function (introduced in Qt 4.4) is not virtual. Instead, subscribedToNotifications() will dynamically detect and call this slot. The default implementation simply returns an empty QStringList. Эта функция была введена в Qt 4.4. See also subscribedToNotifications(). QStringList QSqlDriver::tables ( QSql::TableType tableType ) const [virtual]Returns a list of the names of the 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 backward compatibility. bool QSqlDriver::unsubscribeFromNotification ( const QString & name )This function is called to unsubscribe from event notifications from the database. name identifies the event notification. If successful, return true, otherwise return false. The database must be open when this function is called. All subscribed event notifications are automatically unsubscribed from when the close() function is called. After calling this function the notification() signal will no longer be emitted when an event notification identified by name is posted by the database. Warning: Because of binary compatibility constraints, this function is not virtual. If you want to provide event notification support in your own QSqlDriver subclass, reimplement the unsubscribeFromNotificationImplementation() slot in your subclass instead. The unsubscribeFromNotification() function will dynamically detect the slot and call it. Эта функция была введена в Qt 4.4. See also subscribeToNotification() and subscribedToNotifications(). bool QSqlDriver::unsubscribeFromNotificationImplementation ( const QString & name ) [protected slot]This slot is called to unsubscribe from event notifications from the database. name identifies the event notification. If successful, return true, otherwise return false. The database must be open when this slot is called. All subscribed event notifications are automatically unsubscribed from when the close() function is called. After calling this slot the notification() signal will no longer be emitted when an event notification identified by name is posted by the database. Reimplement this slot to provide your own QSqlDriver subclass with event notification support; because of binary compatibility constraints, the unsubscribeFromNotification() function (introduced in Qt 4.4) is not virtual. Instead, unsubscribeFromNotification() will dynamically detect and call this slot. The default implementation does nothing and returns false. Эта функция была введена в Qt 4.4. See also unsubscribeFromNotification(). |
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