com.trolltech.qt.sql
Class QSqlDatabase

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.sql.QSqlDatabase
All Implemented Interfaces:
QtJambiInterface, java.lang.Cloneable

public class QSqlDatabase
extends QtJambiObject
implements java.lang.Cloneable

The QSqlDatabase class represents a connection to a database. The QSqlDatabase class provides an interface for accessing a database through a connection. An instance of QSqlDatabase represents the connection. The connection provides access to the database via one of the supported database drivers, which are derived from QSqlDriver. Alternatively, you can subclass your own database driver from QSqlDriver. See How to Write Your Own Database Driver for more information.

Create a connection (i.e., an instance of QSqlDatabase) by calling one of the static addDatabase() functions, where you specify the driver or type of driver to use (i.e., what kind of database will you access?) and a connection name. A connection is known by its own name, not by the name of the database it connects to. You can have multiple connections to one database. QSqlDatabase also supports the concept of a default connection, which is the unnamed connection. To create the default connection, don't pass the connection name argument when you call addDatabase(). Subsequently, when you call any static member function that takes the connection name argument, if you don't pass the connection name argument, the default connection is assumed. The following snippet shows how to create and open a default connection to a MySQL database:

        QSqlDatabase db = QSqlDatabase.addDatabase("QPSQL");
        db.setHostName("apollo");
        db.setDatabaseName("customdb");
        db.setUserName("mojito");
        db.setPassword("J0a1m8");
        boolean ok = db.open();
    
Once the QSqlDatabase object has been created, set the connection parameters with setDatabaseName(), setUserName(), setPassword(), setHostName(), setPort(), and setConnectOptions(). Then call open() to activate the physical connection to the database. The connection is not usable until you open it.

The connection defined above will be the default connection, because we didn't give a connection name to addDatabase(). Subsequently, you can get the default connection by calling database() without the connection name argument:

        QSqlDatabase db = QSqlDatabase.database();
    
QSqlDatabase is a value class. Changes made to a database connection via one instance of QSqlDatabase will affect other instances of QSqlDatabase that represent the same connection. Use cloneDatabase() to create an independent database connection based on an existing one.

If you create multiple database connections, specify a unique connection name for each one, when you call addDatabase(). Use database() with a connection name to get that connection. Use removeDatabase() with a connection name to remove a connection. QSqlDatabase outputs a warning if you try to remove a connection referenced by other QSqlDatabase objects. Use contains() to see if a given connection name is in the list of connections.

Once a connection is established, you can call tables() to get the list of tables in the database, call primaryIndex() to get a table's primary index, and call record() to get meta-information about a table's fields (e.g., field names).

Note:QSqlDatabase::exec() is deprecated. Use QSqlQuery::exec() instead.

If the driver supports transactions, use transaction() to start a transaction, and commit() or rollback() to complete it. Use hasFeature() to ask if the driver supports transactions. Note: When using transactions, you must start the transaction before you create your query.

If an error occurrs, lastError() will return information about it.

Get the names of the available SQL drivers with drivers(). Check for the presence of a particular driver with isDriverAvailable(). If you have created your own custom driver, you must register it with registerSqlDriver().

See also:
QSqlDriver, QSqlQuery, QtSql Module, and Threads and the SQL Module.


Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
  QSqlDatabase()
          Creates an empty, invalid QSqlDatabase object.
  QSqlDatabase(QSqlDatabase other)
          Creates a copy of other.
protected QSqlDatabase(QSqlDriver driver)
          This is an overloaded member function, provided for convenience.
protected QSqlDatabase(java.lang.String type)
          This is an overloaded member function, provided for convenience.
 
Method Summary
static QSqlDatabase addDatabase(QSqlDriver driver)
          This overload is useful when you want to create a database connection with a driver you instantiated yourself.
static QSqlDatabase addDatabase(QSqlDriver driver, java.lang.String connectionName)
          This overload is useful when you want to create a database connection with a driver you instantiated yourself.
static QSqlDatabase addDatabase(java.lang.String type)
          Adds a database to the list of database connections using the driver type and the connection name connectionName.
static QSqlDatabase addDatabase(java.lang.String type, java.lang.String connectionName)
          Adds a database to the list of database connections using the driver type and the connection name connectionName.
 QSqlDatabase clone()
          This method is reimplemented for internal reasons
static QSqlDatabase cloneDatabase(QSqlDatabase other, java.lang.String connectionName)
          Clones the database connection other and and stores it as connectionName.
 void close()
          Closes the database connection, freeing any resources acquired, and invalidating any existing QSqlQuery objects that are used with the database.
 boolean commit()
          Commits a transaction to the database if the driver supports transactions and a transaction() has been started.
 java.lang.String connectionName()
          Returns the connection name, which may be empty.
static java.util.List connectionNames()
          Returns a list containing the names of all connections.
 java.lang.String connectOptions()
          Returns the connection options string used for this connection.
static boolean contains()
          Returns true if the list of database connections contains connectionName; otherwise returns false.
static boolean contains(java.lang.String connectionName)
          Returns true if the list of database connections contains connectionName; otherwise returns false.
static QSqlDatabase database()
          Returns the database connection called connectionName.
static QSqlDatabase database(java.lang.String connectionName)
          Returns the database connection called connectionName.
static QSqlDatabase database(java.lang.String connectionName, boolean open)
          Returns the database connection called connectionName.
 java.lang.String databaseName()
          Returns the connection's database name, which may be empty.
static java.lang.String defaultConnection()
          Returns this QSqlDatabase's default connection.
 QSqlDriver driver()
          Returns the database driver used to access the database connection.
 java.lang.String driverName()
          Returns the connection's driver name.
static java.util.List drivers()
          Returns a list of all the available database drivers.
 QSqlQuery exec()
          Executes a SQL statement on the database and returns a QSqlQuery object.
 QSqlQuery exec(java.lang.String query)
          Executes a SQL statement on the database and returns a QSqlQuery object.
 java.lang.String hostName()
          Returns the connection's host name; it may be empty.
static boolean isDriverAvailable(java.lang.String name)
          Returns true if a driver called name is available; otherwise returns false.
 boolean isOpen()
          Returns true if the database connection is currently open; otherwise returns false.
 boolean isOpenError()
          Returns true if there was an error opening the database connection; otherwise returns false.
 boolean isValid()
          Returns true if the QSqlDatabase has a valid driver.
 QSqlError lastError()
          Returns information about the last error that occurred on the database.
 boolean open()
          Opens the database connection using the current connection values.
 boolean open(java.lang.String user, java.lang.String password)
          This is an overloaded member function, provided for convenience.
 java.lang.String password()
          Returns the connection's password.
 int port()
          Returns the connection's port number.
 QSqlIndex primaryIndex(java.lang.String tablename)
          Returns the primary index for table tablename.
 QSqlRecord record(java.lang.String tablename)
          Returns a QSqlRecord populated with the names of all the fields in the table (or view) called tablename.
static void registerSqlDriver(java.lang.String name, QSqlDriverCreatorBase creator)
          This function registers a new SQL driver called name, within the SQL framework.
static void removeDatabase(java.lang.String connectionName)
          Removes the database connection connectionName from the list of database connections.
 boolean rollback()
          Rolls back a transaction on the database, if the driver supports transactions and a transaction() has been started.
 void setConnectOptions()
          Sets database-specific options.
 void setConnectOptions(java.lang.String options)
          Sets database-specific options.
 void setDatabaseName(java.lang.String name)
          Sets the connection's database name to name.
 void setHostName(java.lang.String host)
          Sets the connection's host name to host.
 void setPassword(java.lang.String password)
          Sets the connection's password to password.
 void setPort(int p)
          Sets the connection's port number to port.
 void setUserName(java.lang.String name)
          Sets the connection's user name to name.
 java.util.List tables()
          This is an overloaded method provided for convenience.
 java.util.List tables(QSql.TableType type)
          Returns a list of the database's tables, system tables and views, as specified by the parameter type.
 java.lang.String toString()
          Returns a string representation of the this QSqlDatabase.
 boolean transaction()
          Begins a transaction on the database if the driver supports transactions.
 java.lang.String userName()
          Returns the connection's user name; it may be empty.
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QSqlDatabase

public QSqlDatabase()
Creates an empty, invalid QSqlDatabase object. Use addDatabase(), removeDatabase(), and database() to get valid QSqlDatabase objects.


QSqlDatabase

protected QSqlDatabase(QSqlDriver driver)
This is an overloaded member function, provided for convenience.

Creates a database connection using the given driver.


QSqlDatabase

public QSqlDatabase(QSqlDatabase other)
Creates a copy of other.


QSqlDatabase

protected QSqlDatabase(java.lang.String type)
This is an overloaded member function, provided for convenience.

Creates a QSqlDatabase connection that uses the driver referred to by type. If the type is not recognized, the database connection will have no functionality.

The currently available driver types are:

Driver Type
Description
QDB2 IBM DB2
QIBASE Borland InterBase Driver
QMYSQL MySQL Driver
QOCI Oracle Call Interface Driver
QODBC ODBC Driver (includes Microsoft SQL Server)
QPSQL PostgreSQL Driver
QSQLITE SQLite version 3 or above
QSQLITE2 SQLite version 2
QTDS Sybase Adaptive Server
Additional third party drivers, including your own custom drivers, can be loaded dynamically.

See also:
SQL Database Drivers, registerSqlDriver(), and drivers().

Method Detail

close

public final void close()
Closes the database connection, freeing any resources acquired, and invalidating any existing QSqlQuery objects that are used with the database.

This will also affect copies of this QSqlDatabase object.

See also:
removeDatabase().


commit

public final boolean commit()
Commits a transaction to the database if the driver supports transactions and a transaction() has been started. Returns true if the operation succeeded. Otherwise it returns false.

Note: For some databases, the commit will fail and return false if there is an active query using the database for a SELECT. Make the query inactive before doing the commit.

Call lastError() to get information about errors.

See also:
QSqlQuery::isActive(), QSqlDriver::hasFeature(), and rollback().


connectOptions

public final java.lang.String connectOptions()
Returns the connection options string used for this connection. The string may be empty.

See also:
setConnectOptions().


connectionName

public final java.lang.String connectionName()
Returns the connection name, which may be empty. Note: The connection name is not the database name.

See also:
addDatabase().


databaseName

public final java.lang.String databaseName()
Returns the connection's database name, which may be empty. Note: The database name is not the connection name.

See also:
setDatabaseName().


driver

public final QSqlDriver driver()
Returns the database driver used to access the database connection.

See also:
addDatabase(), and drivers().


driverName

public final java.lang.String driverName()
Returns the connection's driver name.

See also:
addDatabase(), and driver().


exec

public final QSqlQuery exec()
Executes a SQL statement on the database and returns a QSqlQuery object. Use lastError() to retrieve error information. If query is empty, an empty, invalid query is returned and lastError() is not affected.

See also:
QSqlQuery, and lastError().


exec

public final QSqlQuery exec(java.lang.String query)
Executes a SQL statement on the database and returns a QSqlQuery object. Use lastError() to retrieve error information. If query is empty, an empty, invalid query is returned and lastError() is not affected.

See also:
QSqlQuery, and lastError().


hostName

public final java.lang.String hostName()
Returns the connection's host name; it may be empty.

See also:
setHostName().


isOpen

public final boolean isOpen()
Returns true if the database connection is currently open; otherwise returns false.


isOpenError

public final boolean isOpenError()
Returns true if there was an error opening the database connection; otherwise returns false. Error information can be retrieved using the lastError() function.


isValid

public final boolean isValid()
Returns true if the QSqlDatabase has a valid driver.

Example:

        QSqlDatabase db = new QSqlDatabase();
        System.out.println(db.isValid());    // Returns false

        db = QSqlDatabase.database("sales");
        System.out.println(db.isValid());    // Returns true if "sales" connection exists

        QSqlDatabase.removeDatabase("sales");
        System.out.println(db.isValid());    // Returns false


lastError

public final QSqlError lastError()
Returns information about the last error that occurred on the database.

Failures that occur in conjunction with an individual query are reported by QSqlQuery::lastError().

See also:
QSqlError, and QSqlQuery::lastError().


open

public final boolean open()
Opens the database connection using the current connection values. Returns true on success; otherwise returns false. Error information can be retrieved using lastError().

See also:
lastError(), setDatabaseName(), setUserName(), setPassword(), setHostName(), setPort(), and setConnectOptions().


open

public final boolean open(java.lang.String user,
                          java.lang.String password)
This is an overloaded member function, provided for convenience.

Opens the database connection using the given user name and password. Returns true on success; otherwise returns false. Error information can be retrieved using the lastError() function.

This function does not store the password it is given. Instead, the password is passed directly to the driver for opening the connection and it is then discarded.

See also:
lastError().


password

public final java.lang.String password()
Returns the connection's password. If the password was not set with setPassword(), and if the password was given in the open() call, or if no password was used, an empty string is returned.

See also:
setPassword().


port

public final int port()
Returns the connection's port number. The value is undefined if the port number has not been set.

See also:
setPort().


primaryIndex

public final QSqlIndex primaryIndex(java.lang.String tablename)
Returns the primary index for table tablename. If no primary index exists an empty QSqlIndex is returned.

See also:
tables(), and record().


record

public final QSqlRecord record(java.lang.String tablename)
Returns a QSqlRecord populated with the names of all the fields in the table (or view) called tablename. The order in which the fields appear in the record is undefined. If no such table (or view) exists, an empty record is returned.


rollback

public final boolean rollback()
Rolls back a transaction on the database, if the driver supports transactions and a transaction() has been started. Returns true if the operation succeeded. Otherwise it returns false.

Note: For some databases, the rollback will fail and return false if there is an active query using the database for a SELECT. Make the query inactive before doing the rollback.

Call lastError() to get information about errors.

See also:
QSqlQuery::isActive(), QSqlDriver::hasFeature(), and commit().


setConnectOptions

public final void setConnectOptions()
Sets database-specific options. This must be done before the connection is opened or it has no effect (or you can close() the connection, call this function and open() the connection again).

The format of the options string is a semicolon separated list of option names or option=value pairs. The options depend on the database client used:

ODBC
MySQL
PostgreSQL
  • SQL_ATTR_ACCESS_MODE
  • SQL_ATTR_LOGIN_TIMEOUT
  • SQL_ATTR_CONNECTION_TIMEOUT
  • SQL_ATTR_CURRENT_CATALOG
  • SQL_ATTR_METADATA_ID
  • SQL_ATTR_PACKET_SIZE
  • SQL_ATTR_TRACEFILE
  • SQL_ATTR_TRACE
  • SQL_ATTR_CONNECTION_POOLING
  • SQL_ATTR_ODBC_VERSION
  • CLIENT_COMPRESS
  • CLIENT_FOUND_ROWS
  • CLIENT_IGNORE_SPACE
  • CLIENT_SSL
  • CLIENT_ODBC
  • CLIENT_NO_SCHEMA
  • CLIENT_INTERACTIVE
  • UNIX_SOCKET
  • connect_timeout
  • options
  • tty
  • requiressl
  • service
DB2
OCI
TDS
  • SQL_ATTR_ACCESS_MODE
  • SQL_ATTR_LOGIN_TIMEOUT
  • OCI_ATTR_PREFETCH_ROWS
  • OCI_ATTR_PREFETCH_MEMORY
none
SQLite
Interbase
  • QSQLITE_BUSY_TIMEOUT
  • ISC_DPB_LC_CTYPE
  • ISC_DPB_SQL_ROLE_NAME
Examples:
    // ...
    // MySQL connection
    db.setConnectOptions("CLIENT_SSL=1;CLIENT_IGNORE_SPACE=1"); // use an SSL connection to the server
    if (!db.open()) {
        db.setConnectOptions(); // clears the connect option string
    // ...
    }
    // ...
    // PostgreSQL connection
    db.setConnectOptions("requiressl=1"); // enable PostgreSQL SSL connections
    if (!db.open()) {
        db.setConnectOptions(); // clear options
        // ...
    }
    // ...
    // ODBC connection
    db.setConnectOptions("SQL_ATTR_ACCESS_MODE=SQL_MODE_READ_ONLY;SQL_ATTR_TRACE=SQL_OPT_TRACE_ON"); // set ODBC options
    if (!db.open()) {
        db.setConnectOptions(); // don't try to set this option
        // ...
    }
Refer to the client library documentation for more information about the different options.

See also:
connectOptions().


setConnectOptions

public final void setConnectOptions(java.lang.String options)
Sets database-specific options. This must be done before the connection is opened or it has no effect (or you can close() the connection, call this function and open() the connection again).

The format of the options string is a semicolon separated list of option names or option=value pairs. The options depend on the database client used:

ODBC
MySQL
PostgreSQL
  • SQL_ATTR_ACCESS_MODE
  • SQL_ATTR_LOGIN_TIMEOUT
  • SQL_ATTR_CONNECTION_TIMEOUT
  • SQL_ATTR_CURRENT_CATALOG
  • SQL_ATTR_METADATA_ID
  • SQL_ATTR_PACKET_SIZE
  • SQL_ATTR_TRACEFILE
  • SQL_ATTR_TRACE
  • SQL_ATTR_CONNECTION_POOLING
  • SQL_ATTR_ODBC_VERSION
  • CLIENT_COMPRESS
  • CLIENT_FOUND_ROWS
  • CLIENT_IGNORE_SPACE
  • CLIENT_SSL
  • CLIENT_ODBC
  • CLIENT_NO_SCHEMA
  • CLIENT_INTERACTIVE
  • UNIX_SOCKET
  • connect_timeout
  • options
  • tty
  • requiressl
  • service
DB2
OCI
TDS
  • SQL_ATTR_ACCESS_MODE
  • SQL_ATTR_LOGIN_TIMEOUT
  • OCI_ATTR_PREFETCH_ROWS
  • OCI_ATTR_PREFETCH_MEMORY
none
SQLite
Interbase
  • QSQLITE_BUSY_TIMEOUT
  • ISC_DPB_LC_CTYPE
  • ISC_DPB_SQL_ROLE_NAME
Examples:
    // ...
    // MySQL connection
    db.setConnectOptions("CLIENT_SSL=1;CLIENT_IGNORE_SPACE=1"); // use an SSL connection to the server
    if (!db.open()) {
        db.setConnectOptions(); // clears the connect option string
    // ...
    }
    // ...
    // PostgreSQL connection
    db.setConnectOptions("requiressl=1"); // enable PostgreSQL SSL connections
    if (!db.open()) {
        db.setConnectOptions(); // clear options
        // ...
    }
    // ...
    // ODBC connection
    db.setConnectOptions("SQL_ATTR_ACCESS_MODE=SQL_MODE_READ_ONLY;SQL_ATTR_TRACE=SQL_OPT_TRACE_ON"); // set ODBC options
    if (!db.open()) {
        db.setConnectOptions(); // don't try to set this option
        // ...
    }
Refer to the client library documentation for more information about the different options.

See also:
connectOptions().


setDatabaseName

public final void setDatabaseName(java.lang.String name)
Sets the connection's database name to name. To have effect, the database name must be set before the connection is opened. Alternatively, you can close() the connection, set the database name, and call open() again. Note: The database name is not the connection name. The connection name must be passed to addDatabase() at connection object create time.

For the QOCI (Oracle) driver, the database name is the TNS Service Name.

For the QODBC driver, the name can either be a DSN, a DSN filename (in which case the file must have a .dsn extension), or a connection string.

For example, Microsoft Access users can use the following connection string to open an .mdb file directly, instead of having to create a DSN entry in the ODBC manager:

    // ...
    db = QSqlDatabase.addDatabase("QODBC");
    db.setDatabaseName("DRIVER={Microsoft Access Driver (*.mdb)};FIL={MS Access};DBQ=myaccessfile.mdb");
    if (db.open()) {
        // success!
    }
    // ...
There is no default value.

See also:
databaseName(), setUserName(), setPassword(), setHostName(), setPort(), setConnectOptions(), and open().


setHostName

public final void setHostName(java.lang.String host)
Sets the connection's host name to host. To have effect, the host name must be set before the connection is opened. Alternatively, you can close() the connection, set the host name, and call open() again.

There is no default value.

See also:
hostName(), setUserName(), setPassword(), setDatabaseName(), setPort(), setConnectOptions(), and open().


setPassword

public final void setPassword(java.lang.String password)
Sets the connection's password to password. To have effect, the password must be set before the connection is opened. Alternatively, you can close() the connection, set the password, and call open() again.

There is no default value.

Warning: This function stores the password in plain text within Qt. Use the open() call that takes a password as parameter to avoid this behavior.

See also:
password(), setUserName(), setDatabaseName(), setHostName(), setPort(), setConnectOptions(), and open().


setPort

public final void setPort(int p)
Sets the connection's port number to port. To have effect, the port number must be set before the connection is opened. Alternatively, you can close() the connection, set the port number, and call open() again..

There is no default value.

See also:
port(), setUserName(), setPassword(), setHostName(), setDatabaseName(), setConnectOptions(), and open().


setUserName

public final void setUserName(java.lang.String name)
Sets the connection's user name to name. To have effect, the user name must be set before the connection is opened. Alternatively, you can close() the connection, set the user name, and call open() again.

There is no default value.

See also:
userName(), setDatabaseName(), setPassword(), setHostName(), setPort(), setConnectOptions(), and open().


tables

public final java.util.List tables()
This is an overloaded method provided for convenience.


tables

public final java.util.List tables(QSql.TableType type)
Returns a list of the database's tables, system tables and views, as specified by the parameter type.

See also:
primaryIndex(), and record().


transaction

public final boolean transaction()
Begins a transaction on the database if the driver supports transactions. Returns true if the operation succeeded. Otherwise it returns false.

See also:
QSqlDriver::hasFeature(), commit(), and rollback().


userName

public final java.lang.String userName()
Returns the connection's user name; it may be empty.

See also:
setUserName().


addDatabase

public static QSqlDatabase addDatabase(QSqlDriver driver)
This overload is useful when you want to create a database connection with a driver you instantiated yourself. It might be your own database driver, or you might just need to instantiate one of the Qt drivers yourself. If you do this, it is recommended that you include the driver code in your application. For example, you can create a PostgreSQL connection with your own QPSQL driver like this:
        #include "qtdir/src/sql/drivers/psql/qsql_psql.cpp"

PGconn on = PQconnectdb("host=server user=bart password=simpson dbname=springfield"); QPSQLDriver rv = new QPSQLDriver(con); QSqlDatabase db = QSqlDatabase.addDatabase(drv); // becomes the new default connection QSqlQuery query; query.exec("SELECT NAME, ID FROM STAFF"); // ...
The above code sets up a PostgreSQL connection and instantiates a QPSQLDriver object. Next, addDatabase() is called to add the connection to the known connections so that it can be used by the Qt SQL classes. When a driver is instantiated with a connection handle (or set of handles), Qt assumes that you have already opened the database connection.

Note: We assume that qtdir is the directory where Qt is installed. This will pull in the code that is needed to use the PostgreSQL client library and to instantiate a QPSQLDriver object, assuming that you have the PostgreSQL headers somewhere in your include search path.

Remember that you must link your application against the database client library. Make sure the client library is in your linker's search path, and add lines like these to your .pro file:

         unix:LIBS += -lpq
     win32:LIBS += libpqdll.lib
The method described works for all the supplied drivers. The only difference will be in the driver constructor arguments. Here is a table of the drivers included with Qt, their source code files, and their constructor arguments:
Driver
Class name
Constructor arguments
File to include
QPSQL QPSQLDriver PGconn *connection qsql_psql.cpp
QMYSQL QMYSQLDriver MYSQL *connection qsql_mysql.cpp
QOCI QOCIDriver OCIEnv *environment, OCISvcCtx *serviceContext qsql_oci.cpp
QODBC QODBCDriver SQLHANDLE environment, SQLHANDLE connection qsql_odbc.cpp
QDB2 QDB2 SQLHANDLE environment, SQLHANDLE connection qsql_db2.cpp
QTDS QTDSDriver LOGINREC *loginRecord, DBPROCESS *dbProcess, const QString &hostName qsql_tds.cpp
QSQLITE QSQLiteDriver sqlite *connection qsql_sqlite.cpp
QIBASE QIBaseDriver isc_db_handle connection qsql_ibase.cpp
The host name (or service name) is needed when constructing the QTDSDriver for creating new connections for internal queries. This is to prevent blocking when several QSqlQuery objects are used simultaneously.

Warning: Adding a database connection with the same connection name as an existing connection, causes the existing connection to be replaced by the new one.

Warning: The SQL framework takes ownership of the driver. It must not be deleted. To remove the connection, use removeDatabase().

See also:
drivers().


addDatabase

public static QSqlDatabase addDatabase(QSqlDriver driver,
                                       java.lang.String connectionName)
This overload is useful when you want to create a database connection with a driver you instantiated yourself. It might be your own database driver, or you might just need to instantiate one of the Qt drivers yourself. If you do this, it is recommended that you include the driver code in your application. For example, you can create a PostgreSQL connection with your own QPSQL driver like this:
        #include "qtdir/src/sql/drivers/psql/qsql_psql.cpp"

PGconn on = PQconnectdb("host=server user=bart password=simpson dbname=springfield"); QPSQLDriver rv = new QPSQLDriver(con); QSqlDatabase db = QSqlDatabase.addDatabase(drv); // becomes the new default connection QSqlQuery query; query.exec("SELECT NAME, ID FROM STAFF"); // ...
The above code sets up a PostgreSQL connection and instantiates a QPSQLDriver object. Next, addDatabase() is called to add the connection to the known connections so that it can be used by the Qt SQL classes. When a driver is instantiated with a connection handle (or set of handles), Qt assumes that you have already opened the database connection.

Note: We assume that qtdir is the directory where Qt is installed. This will pull in the code that is needed to use the PostgreSQL client library and to instantiate a QPSQLDriver object, assuming that you have the PostgreSQL headers somewhere in your include search path.

Remember that you must link your application against the database client library. Make sure the client library is in your linker's search path, and add lines like these to your .pro file:

         unix:LIBS += -lpq
     win32:LIBS += libpqdll.lib
The method described works for all the supplied drivers. The only difference will be in the driver constructor arguments. Here is a table of the drivers included with Qt, their source code files, and their constructor arguments:
Driver
Class name
Constructor arguments
File to include
QPSQL QPSQLDriver PGconn *connection qsql_psql.cpp
QMYSQL QMYSQLDriver MYSQL *connection qsql_mysql.cpp
QOCI QOCIDriver OCIEnv *environment, OCISvcCtx *serviceContext qsql_oci.cpp
QODBC QODBCDriver SQLHANDLE environment, SQLHANDLE connection qsql_odbc.cpp
QDB2 QDB2 SQLHANDLE environment, SQLHANDLE connection qsql_db2.cpp
QTDS QTDSDriver LOGINREC *loginRecord, DBPROCESS *dbProcess, const QString &hostName qsql_tds.cpp
QSQLITE QSQLiteDriver sqlite *connection qsql_sqlite.cpp
QIBASE QIBaseDriver isc_db_handle connection qsql_ibase.cpp
The host name (or service name) is needed when constructing the QTDSDriver for creating new connections for internal queries. This is to prevent blocking when several QSqlQuery objects are used simultaneously.

Warning: Adding a database connection with the same connection name as an existing connection, causes the existing connection to be replaced by the new one.

Warning: The SQL framework takes ownership of the driver. It must not be deleted. To remove the connection, use removeDatabase().

See also:
drivers().


addDatabase

public static QSqlDatabase addDatabase(java.lang.String type)
Adds a database to the list of database connections using the driver type and the connection name connectionName. If there already exists a database connection called connectionName, that connection is removed.

The database connection is referred to by connectionName. The newly added database connection is returned.

If connectionName is not specified, the new connection becomes the default connection for the application, and subsequent calls to database() without the connection name argument will return the default connection. If a connectionName is provided here, use database(connectionName) to retrieve the connection.

Warning: If you add a connection with the same name as an existing connection, the new connection replaces the old one. If you call this function more than once without specifying connectionName, the default connection will be the one replaced.

Before using the connection, it must be initialized. e.g., call some or all of setDatabaseName(), setUserName(), setPassword(), setHostName(), setPort(), and setConnectOptions(), and, finally, open().

See also:
database(), removeDatabase(), and Threads and the SQL Module.


addDatabase

public static QSqlDatabase addDatabase(java.lang.String type,
                                       java.lang.String connectionName)
Adds a database to the list of database connections using the driver type and the connection name connectionName. If there already exists a database connection called connectionName, that connection is removed.

The database connection is referred to by connectionName. The newly added database connection is returned.

If connectionName is not specified, the new connection becomes the default connection for the application, and subsequent calls to database() without the connection name argument will return the default connection. If a connectionName is provided here, use database(connectionName) to retrieve the connection.

Warning: If you add a connection with the same name as an existing connection, the new connection replaces the old one. If you call this function more than once without specifying connectionName, the default connection will be the one replaced.

Before using the connection, it must be initialized. e.g., call some or all of setDatabaseName(), setUserName(), setPassword(), setHostName(), setPort(), and setConnectOptions(), and, finally, open().

See also:
database(), removeDatabase(), and Threads and the SQL Module.


cloneDatabase

public static QSqlDatabase cloneDatabase(QSqlDatabase other,
                                         java.lang.String connectionName)
Clones the database connection other and and stores it as connectionName. All the settings from the original database, e.g. databaseName(), hostName(), etc., are copied across. Does nothing if other is an invalid database. Returns the newly created database connection.

Note: The new connection has not been opened. Before using the new connection, you must call open().


connectionNames

public static java.util.List connectionNames()
Returns a list containing the names of all connections.

See also:
contains(), database(), and Threads and the SQL Module.


contains

public static boolean contains()
Returns true if the list of database connections contains connectionName; otherwise returns false.

See also:
connectionNames(), database(), and Threads and the SQL Module.


contains

public static boolean contains(java.lang.String connectionName)
Returns true if the list of database connections contains connectionName; otherwise returns false.

See also:
connectionNames(), database(), and Threads and the SQL Module.


database

public static QSqlDatabase database(java.lang.String connectionName)
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, an invalid connection is returned.

See also:
isOpen(), and Threads and the SQL Module.


database

public static QSqlDatabase database()
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, an invalid connection is returned.

See also:
isOpen(), and Threads and the SQL Module.


database

public static QSqlDatabase database(java.lang.String connectionName,
                                    boolean open)
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, an invalid connection is returned.

See also:
isOpen(), and Threads and the SQL Module.


drivers

public static java.util.List drivers()
Returns a list of all the available database drivers.

See also:
registerSqlDriver().


isDriverAvailable

public static boolean isDriverAvailable(java.lang.String name)
Returns true if a driver called name is available; otherwise returns false.

See also:
drivers().


registerSqlDriver

public static void registerSqlDriver(java.lang.String name,
                                     QSqlDriverCreatorBase creator)
This function registers a new SQL driver called name, within the SQL framework. This is useful if you have a custom SQL driver and don't want to compile it as a plugin.

Example:

     QSqlDatabase.registerSqlDriver("MYDRIVER",
                                     new QSqlDriverCreator<MyDatabaseDriver>);
     QSqlDatabase db = QSqlDatabase.addDatabase("MYDRIVER");
QSqlDatabase takes ownership of the creator pointer, so you mustn't delete it yourself.

See also:
drivers().


removeDatabase

public static void removeDatabase(java.lang.String connectionName)
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.

Example:

    // WRONG
    QSqlDatabase db = QSqlDatabase.database("sales");
    QSqlQuery query = new QSqlQuery("SELECT NAME, DOB FROM EMPLOYEES", db);
    QSqlDatabase.removeDatabase("sales"); // will output a warning

    // "db" is now a dangling invalid database connection,
    // "query" contains an invalid result set
The correct way to do it:
    {
        QSqlDatabase db = QSqlDatabase.database("sales");
        QSqlQuery query = new QSqlQuery("SELECT NAME, DOB FROM EMPLOYEES", db);
    }
    // Both "db" and "query" are destroyed because they are out of scope
    QSqlDatabase.removeDatabase("sales"); // correct
To remove the default connection, which may have been created with a call to addDatabase() not specifying a connection name, you can retrieve the default connection name by calling connectionName() on the database returned by database(). Note that if a default database hasn't been created an invalid database will be returned.

See also:
database(), connectionName(), and Threads and the SQL Module.


defaultConnection

public static java.lang.String defaultConnection()
Returns this QSqlDatabase's default connection.


toString

public java.lang.String toString()
Returns a string representation of the this QSqlDatabase.

Overrides:
toString in class java.lang.Object

clone

public QSqlDatabase clone()
This method is reimplemented for internal reasons

Overrides:
clone in class java.lang.Object