CopperSpice API  1.7.2
QSqlDatabase Class Reference

The QSqlDatabase class represents a connection to a database. More...

Public Methods

 QSqlDatabase ()
 
 QSqlDatabase (const QSqlDatabase &other)
 
 ~QSqlDatabase ()
 
void close ()
 
bool commit ()
 
QString connectionName () const
 
QString connectOptions () const
 
QString databaseName () const
 
QSqlDriverdriver () const
 
QString driverName () const
 
QSqlQuery exec (const QString &query=QString ()) const
 
QString hostName () const
 
bool isOpen () const
 
bool isOpenError () const
 
bool isValid () const
 
QSqlError lastError () const
 
QSql::NumericalPrecisionPolicy numericalPrecisionPolicy () const
 
bool open ()
 
bool open (const QString &user, const QString &password)
 
QSqlDatabase & operator= (const QSqlDatabase &other)
 
QString password () const
 
int port () const
 
QSqlIndex primaryIndex (const QString &tablename) const
 
QSqlRecord record (const QString &tablename) const
 
bool rollback ()
 
void setConnectOptions (const QString &options=QString ())
 
void setDatabaseName (const QString &name)
 
void setHostName (const QString &host)
 
void setNumericalPrecisionPolicy (QSql::NumericalPrecisionPolicy precisionPolicy)
 
void setPassword (const QString &password)
 
void setPort (int port)
 
void setUserName (const QString &name)
 
QStringList tables (QSql::TableType type=QSql::Tables) const
 
bool transaction ()
 
QString userName () const
 

Static Public Methods

static QSqlDatabase addDatabase (const QString &type, const QString &connectionName=defaultConnection)
 
static QSqlDatabase addDatabase (QSqlDriver *driver, const QString &connectionName=defaultConnection)
 
static QSqlDatabase cloneDatabase (const QSqlDatabase &other, const QString &connectionName)
 
static QStringList connectionNames ()
 
static bool contains (const QString &connectionName=defaultConnection)
 
static QSqlDatabase database (const QString &connectionName=defaultConnection, bool open=true)
 
static QStringList drivers ()
 
static bool isDriverAvailable (const QString &name)
 
static void registerSqlDriver (const QString &name, QSqlDriverCreatorBase *creator)
 
static void removeDatabase (const QString &connectionName)
 

Protected Methods

 QSqlDatabase (const QString &type)
 
 QSqlDatabase (QSqlDriver *driver)
 

Detailed Description

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 SQL Database Drivers, which inherit from QSqlDriver. Refer to SQL Drivers for a list of supported drivers.

You can inherit from QSqlDriver and write your own database driver.

To create a connection (an instance of QSqlDatabase), call one of the static addDatabase() methods. Specify a supported SQL Database Driver 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, do not 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 do not pass the connection name argument, the default connection is assumed. The following snippet shows how to create and open a default connection to a PostgreSQL database:

db.setHostName("example.com");
db.setDatabaseName("customDB");
db.setUserName("my_username");
db.setPassword("my_password");
bool 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 did not give a connection name to addDatabase(). Subsequently, you can get the default connection by calling database() without the connection name argument:

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 occurs, 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, CsSql library, Threads in SQL

Constructor & Destructor Documentation

QSqlDatabase::QSqlDatabase ( )

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

QSqlDatabase::QSqlDatabase ( const QSqlDatabase &  other)

Creates a copy of other.

QSqlDatabase::~QSqlDatabase ( )

Destroys the object and frees any allocated resources.

See also
close()
QSqlDatabase::QSqlDatabase ( const QString type)
explicitprotected

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 TypeDescription
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
QTDS Sybase Adaptive Server

Additional third party drivers, including your own custom drivers, can be loaded dynamically.

See also
SQL Drivers, registerSqlDriver(), drivers()
QSqlDatabase::QSqlDatabase ( QSqlDriver driver)
explicitprotected

Creates a database connection using the given driver.

Method Documentation

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. 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 type is not available or could not be loaded, isValid() returns false.

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().

Note
This method is thread-safe.
See also
database(), removeDatabase(), Threads in SQL
QSqlDatabase QSqlDatabase::addDatabase ( QSqlDriver driver,
const QString connectionName = defaultConnection 
)
static

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 CopperSpice 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 *con = PQconnectdb("host=server user=bart password=simpson dbname=springfield");
QPSQLDriver *drv = 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 CopperSpice SQL classes. When a driver is instantiated with a connection handle (or set of handles), CopperSpice assumes you have already opened the database connection.

Note
We assume that qtdir is the directory where CopperSpice 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.

You must link your application with the database client library.

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 CopperSpice.

DriverClass nameConstructor argumentsFile to include
QPSQLQPSQLDriverPGconn *connectionqsql_psql.cpp
QMYSQLQMYSQLDriverMYSQL *connectionqsql_mysql.cpp
QOCIQOCIDriverOCIEnv *environment, OCISvcCtx *serviceContextqsql_oci.cpp
QODBCQODBCDriverSQLHANDLE environment, SQLHANDLE connectionqsql_odbc.cpp
QDB2QDB2SQLHANDLE environment, SQLHANDLE connection qsql_db2.cpp
QTDSQTDSDriver LOGINREC *loginRecord, DBPROCESS *dbProcess, const QString &hostName qsql_tds.cpp
QSQLITEQSQLiteDriver sqlite *connection qsql_sqlite.cpp
QIBASEQIBaseDriver 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.
The SQL database takes ownership of the driver and it must not be deleted. To remove the connection, use removeDatabase().
See also
drivers()
QSqlDatabase QSqlDatabase::cloneDatabase ( const QSqlDatabase &  other,
const QString connectionName 
)
static

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().
void QSqlDatabase::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()
bool QSqlDatabase::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(), rollback()
QString QSqlDatabase::connectionName ( ) const

Returns the connection name, which may be empty. The connection name is not the database name.

See also
addDatabase()
QStringList QSqlDatabase::connectionNames ( )
static

Returns a list containing the names of all connections.

Note
This method is thread-safe.
See also
contains(), database(), Threads in SQL
QString QSqlDatabase::connectOptions ( ) const

Returns the connection options string used for this connection. The string may be empty.

See also
setConnectOptions()
bool QSqlDatabase::contains ( const QString connectionName = defaultConnection)
static

Returns true if the list of database connections contains connectionName, otherwise returns false.

Note
This method is thread-safe.
See also
connectionNames(), database(), Threads in SQL
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, an invalid connection is returned.

Note
This method is thread-safe.
See also
isOpen(), Threads in SQL
QString QSqlDatabase::databaseName ( ) const

Returns the connection's database name, which may be empty.

Note
The database name is not the connection name.
See also
setDatabaseName()
QSqlDriver * QSqlDatabase::driver ( ) const

Returns the database driver used to access the database connection.

See also
addDatabase(), drivers()
QString QSqlDatabase::driverName ( ) const

Returns the connection's driver name.

See also
addDatabase(), driver()
QStringList QSqlDatabase::drivers ( )
static

Returns a list of all the available database drivers.

See also
registerSqlDriver()
QSqlQuery QSqlDatabase::exec ( const QString query = QString()) const

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, lastError()
QString QSqlDatabase::hostName ( ) const

Returns the connection's host name; it may be empty.

See also
setHostName()
bool QSqlDatabase::isDriverAvailable ( const QString name)
static

Returns true if a driver called name is available, otherwise returns false.

See also
drivers()
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.

bool QSqlDatabase::isValid ( ) const

Returns true if the QSqlDatabase has a valid driver.

qDebug() << db.isValid(); // Returns false
db = QSqlDatabase::database("sales");
qDebug() << db.isValid(); // Returns true if "sales" connection exists
qDebug() << db.isValid(); // Returns false
QSqlError QSqlDatabase::lastError ( ) const

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, QSqlQuery::lastError()
QSql::NumericalPrecisionPolicy QSqlDatabase::numericalPrecisionPolicy ( ) const
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 lastError().

See also
lastError(), setDatabaseName(), setUserName(), setPassword(), setHostName(), setPort(), setConnectOptions()
bool QSqlDatabase::open ( const QString user,
const QString password 
)

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()
QSqlDatabase & QSqlDatabase::operator= ( const QSqlDatabase &  other)

Assigns other to this object.

QString QSqlDatabase::password ( ) const

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()
int QSqlDatabase::port ( ) const

Returns the connection's port number. The value is undefined if the port number has not been set.

See also
setPort()
QSqlIndex QSqlDatabase::primaryIndex ( const QString tablename) const

Returns the primary index for table tablename. If no primary index exists an empty QSqlIndex is returned.

See also
tables(), record()
QSqlRecord QSqlDatabase::record ( const QString tablename) const

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.

void QSqlDatabase::registerSqlDriver ( const QString name,
QSqlDriverCreatorBase creator 
)
static

Registers a new SQL driver called name. This is useful if there is a custom SQL driver and it is not a plugin.

QSqlDatabase takes ownership of the creator pointer, so you must not delete it yourself.

See also
drivers()
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.
QSqlDatabase db = QSqlDatabase::database("sales"); // incorrect
QSqlQuery query("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

This is the correct way.

{
QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db);
}
// Both "db" and "query" are destroyed because they are out of scope

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 has not been created an invalid database will be returned.

This method is thread-safe.

See also
database(), connectionName(), Threads in SQL
bool QSqlDatabase::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(), commit()
void QSqlDatabase::setConnectOptions ( const QString options = QString())

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:

ODBCMySQLPostgreSQL
  • 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
  • MYSQL_OPT_RECONNECT
  • connect_timeout
  • options
  • tty
  • requiressl
  • service
DB2OCITDS
  • SQL_ATTR_ACCESS_MODE
  • SQL_ATTR_LOGIN_TIMEOUT
  • OCI_ATTR_PREFETCH_ROWS
  • OCI_ATTR_PREFETCH_MEMORY
none
SQLiteInterbase
  • QSQLITE_BUSY_TIMEOUT
  • QSQLITE_OPEN_READONLY
  • QSQLITE_ENABLE_SHARED_CACHE
  • 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(); // do not try to set this option
...
}

Refer to the client library documentation for more information about the different options.

See also
connectOptions()
void QSqlDatabase::setDatabaseName ( const QString 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.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(), open()
void QSqlDatabase::setHostName ( const QString 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(), open()
void QSqlDatabase::setNumericalPrecisionPolicy ( QSql::NumericalPrecisionPolicy  precisionPolicy)

Sets the default numerical precision policy used by queries created on this database connection to precisionPolicy.

Note: Drivers that do not support fetching numerical values with low precision will ignore the precision policy. You can use QSqlDriver::hasFeature() to find out whether a driver supports this feature.

Note: Setting the default precision policy to precisionPolicy does not affect any currently active queries.

See also
QSql::NumericalPrecisionPolicy, numericalPrecisionPolicy(), QSqlQuery::setNumericalPrecisionPolicy(), QSqlQuery::numericalPrecisionPolicy()
void QSqlDatabase::setPassword ( const QString 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 CopperSpice. Use the open() call that takes a password as parameter to avoid this behavior.
See also
password(), setUserName(), setDatabaseName(), setHostName(), setPort(), setConnectOptions(), open()
void QSqlDatabase::setPort ( int  port)

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(), open()
void QSqlDatabase::setUserName ( const QString 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(), open()
QStringList QSqlDatabase::tables ( QSql::TableType  type = QSql::Tables) const

Returns a list of the database's tables, system tables and views, as specified by the parameter type.

See also
primaryIndex(), record()
bool QSqlDatabase::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(), rollback()
QString QSqlDatabase::userName ( ) const

Returns the connection's user name; it may be empty.

See also
setUserName()