QSqlDatabase(3qt)QSqlDatabase(3qt)NAMEQSqlDatabase - Used to create SQL database connections and to provide
transaction handling
SYNOPSIS
#include <qsqldatabase.h>
Inherits QObject.
Public Members
~QSqlDatabase ()
bool open ()
bool open ( const QString & user, const QString & password )
void close ()
bool isOpen () const
bool isOpenError () const
QStringList tables () const
QStringList tables ( QSql::TableType type ) const
QSqlIndex primaryIndex ( const QString & tablename ) const
QSqlRecord record ( const QString & tablename ) const
QSqlRecord record ( const QSqlQuery & query ) const
QSqlRecordInfo recordInfo ( const QString & tablename ) const
QSqlRecordInfo recordInfo ( const QSqlQuery & query ) const
QSqlQuery exec ( const QString & query = QString::null ) const
QSqlError lastError () const
bool transaction ()
bool commit ()
bool rollback ()
virtual void setDatabaseName ( const QString & name )
virtual void setUserName ( const QString & name )
virtual void setPassword ( const QString & password )
virtual void setHostName ( const QString & host )
virtual void setPort ( int p )
void setConnectOptions ( const QString & options = QString::null )
QString databaseName () const
QString userName () const
QString password () const
QString hostName () const
QString driverName () const
int port () const
QString connectOptions () const
QSqlDriver * driver () const
Static Public Members
QSqlDatabase * addDatabase ( const QString & type, const QString &
connectionName = defaultConnection )
QSqlDatabase * addDatabase ( QSqlDriver * driver, const QString &
connectionName = defaultConnection )
QSqlDatabase * database ( const QString & connectionName =
defaultConnection, bool open = TRUE )
void removeDatabase ( const QString & connectionName )
void removeDatabase ( QSqlDatabase * db )
bool contains ( const QString & connectionName = defaultConnection )
QStringList drivers ()
void registerSqlDriver ( const QString & name, const
QSqlDriverCreatorBase * creator )
bool isDriverAvailable ( const QString & name )
Properties
QString connectOptions - the database connect options
QString databaseName - the name of the database
QString hostName - the host name where the database resides
QString password - the password used to connect to the database
int port - the port used to connect to the database
QString userName - the user name connected to the database
Protected Members
QSqlDatabase ( const QString & type, const QString & name, QObject *
parent = 0, const char * objname = 0 )
QSqlDatabase ( QSqlDriver * driver, QObject * parent = 0, const char *
objname = 0 )
DESCRIPTION
The QSqlDatabase class is used to create SQL database connections and
to provide transaction handling.
Note that transaction handling is not supported by every SQL database.
You can find out whether transactions are supported using
QSqlDriver::hasFeature().
The QSqlDatabase class provides an abstract interface for accessing
many types of database backends. Database-specific drivers are used
internally to actually access and manipulate data, (see QSqlDriver).
Result set objects provide the interface for executing and manipulating
SQL queries (see QSqlQuery).
See also Database Classes.
MEMBER FUNCTION DOCUMENTATIONQSqlDatabase::QSqlDatabase ( const QString & type, const QString & name,
QObject * parent = 0, const char * objname = 0 ) [protected]
Creates a QSqlDatabase connection called name that uses the driver
referred to by type, with the parent parent and the object name
objname. If the type is not recognized, the database connection will
have no functionality.
The currently available drivers are:
<center>.nf
</center>
Additional third party drivers, including your own custom drivers, can
be loaded dynamically.
See also registerSqlDriver().
QSqlDatabase::QSqlDatabase ( QSqlDriver * driver, QObject * parent = 0, const
char * objname = 0 ) [protected]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Creates a database connection using the driver driver, with the parent
parent and the object name objname.
Warning: The framework takes ownership of the driver pointer, so it
should not be deleted.
QSqlDatabase::~QSqlDatabase ()
Destroys the object and frees any allocated resources.
QSqlDatabase * QSqlDatabase::addDatabase ( const QString & type, const QString
& connectionName = defaultConnection ) [static]
Adds a database to the list of database connections using the driver
type and the connection name connectionName.
The database connection is referred to by connectionName. The newly
added database connection is returned. This pointer is owned by
QSqlDatabase and will be deleted on program exit or when
removeDatabase() is called.
If connectionName is not specified, the newly added database connection
becomes the default database connection for the application, and
subsequent calls to database() (without a database name parameter) will
return a pointer to it. If connectionName is given, use
database(connectionName) to retrieve a pointer to the database
connection.
Warning: If you add a database with the same name as an existing
database, the new database will replace the old one. This will happen
automatically if you call this function more than once without
specifying connectionName.
See also database() and removeDatabase().
Examples:
QSqlDatabase * QSqlDatabase::addDatabase ( QSqlDriver * driver, const QString
& connectionName = defaultConnection ) [static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
This function is useful if you need to set up the database connection
and instantiate the driver yourself. If you do this, it is recommended
that you include the driver code in your own application. For example,
setting up a custom PostgreSQL connection and instantiating the QPSQL7
driver can be done the following way:
#include "qtdir/src/sql/drivers/psql/qsql_psql.cpp"
(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.
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 q;
q.exec( "SELECT * FROM people" );
...
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.
Remember that you must link your application against the database
client library as well. The simplest way to do this is to add lines
like those below to your .pro file:
unix:LIBS += -lpq
win32:LIBS += libpqdll.lib
You will need to have the client library in your linker's search path.
The method described above will work for all the drivers, the only
difference is the arguments the driver constructors take. Below is an
overview of the drivers and their constructor arguments.
<center>.nf
</center>
Note: The host name (or service name) is needed when constructing the
QTDSDriver for creating new connections for internal queries. This is
to prevent the simultaneous usage of several QSqlQuery/QSqlCursor
objects from blocking each other.
Warning: The SQL framework takes ownership of the driver pointer, and
it should not be deleted. The returned QSqlDatabase object is owned by
the framework and must not be deleted. If you want to explicitly remove
the connection, use removeDatabase()
See also drivers().
void QSqlDatabase::close ()
Closes the database connection, freeing any resources acquired.
See also removeDatabase().
bool QSqlDatabase::commit ()
Commits a transaction to the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature() and rollback().
QString QSqlDatabase::connectOptions () const
Returns the database connect options. See the "connectOptions" property
for details.
bool QSqlDatabase::contains ( const QString & connectionName =
defaultConnection ) [static]
Returns TRUE if the list of database connections contains
connectionName; otherwise returns FALSE.
QSqlDatabase * QSqlDatabase::database ( const QString & connectionName =
defaultConnection, bool open = TRUE ) [static]
Returns the database connection called connectionName. The database
connection must have been previously added with addDatabase(). If open
is TRUE (the default) and the database connection is not already open
it is opened now. If no connectionName is specified the default
connection is used. If connectionName does not exist in the list of
databases, 0 is returned. The pointer returned is owned by QSqlDatabase
and should not be deleted.
Warning: There are restrictions on the use of database connections in
threaded applications. Please see the Thread Support in Qt document for
more information about threading and SQL databases.
Examples:
QString QSqlDatabase::databaseName () const
Returns the name of the database. See the "databaseName" property for
details.
QSqlDriver * QSqlDatabase::driver () const
Returns the database driver used to access the database connection.
QString QSqlDatabase::driverName () const
Returns the name of the driver used by the database connection.
QStringList QSqlDatabase::drivers () [static]
Returns a list of all the available database drivers.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = QSqlDatabase::drivers();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
QSqlQuery QSqlDatabase::exec ( const QString & query = QString::null ) const
Executes a SQL statement (e.g. an INSERT, UPDATE or DELETE statement)
on the database, and returns a QSqlQuery object. Use lastError() to
retrieve error information. If query is QString::null, an empty,
invalid query is returned and lastError() is not affected.
See also QSqlQuery and lastError().
QString QSqlDatabase::hostName () const
Returns the host name where the database resides. See the "hostName"
property for details.
bool QSqlDatabase::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.
QSqlError QSqlDatabase::lastError () const
Returns information about the last error that occurred on the database.
See QSqlError for more information.
Examples:
bool QSqlDatabase::open ()
Opens the database connection using the current connection values.
Returns TRUE on success; otherwise returns FALSE. Error information can
be retrieved using the lastError() function.
See also lastError().
Examples:
bool QSqlDatabase::open ( const QString & user, const QString & password )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Opens the database connection using 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 a connection and
is then discarded.
See also lastError().
QString QSqlDatabase::password () const
Returns the password used to connect to the database. See the
"password" property for details.
int QSqlDatabase::port () const
Returns the port used to connect to the database. See the "port"
property for details.
QSqlIndex QSqlDatabase::primaryIndex ( const QString & tablename ) const
Returns the primary index for table tablename. If no primary index
exists an empty QSqlIndex will be returned.
QSqlRecord QSqlDatabase::record ( const QString & tablename ) const
Returns a QSqlRecord populated with the names of all the fields in the
table (or view) 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.
See also recordInfo().
QSqlRecord QSqlDatabase::record ( const QSqlQuery & query ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a QSqlRecord populated with the names of all the fields used in
the SQL query. If the query is a "SELECT *" the order in which fields
appear in the record is undefined.
See also recordInfo().
QSqlRecordInfo QSqlDatabase::recordInfo ( const QString & tablename ) const
Returns a QSqlRecordInfo populated with meta data about the table or
view tablename. If no such table (or view) exists, an empty record is
returned.
See also QSqlRecordInfo, QSqlFieldInfo, and record().
QSqlRecordInfo QSqlDatabase::recordInfo ( const QSqlQuery & query ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a QSqlRecordInfo object with meta data for the QSqlQuery query.
Note that this overloaded function may return less information than the
recordInfo() function which takes the name of a table as parameter.
See also QSqlRecordInfo, QSqlFieldInfo, and record().
void QSqlDatabase::registerSqlDriver ( const QString & name, const
QSqlDriverCreatorBase * creator ) [static]
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 usage:
QSqlDatabase::registerSqlDriver( "MYDRIVER", new QSqlDriverCreator<MyDatabaseDriver> );
QSqlDatabase* db = QSqlDatabase::addDatabase( "MYDRIVER" );
...
Warning: The framework takes ownership of the creator pointer, so it
should not be deleted.
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.
void QSqlDatabase::removeDatabase ( QSqlDatabase * db ) [static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Removes the database connection db from the list of database
connections. The QSqlDatabase object is destroyed when it is removed
from the list.
Warning: The db pointer is not valid after this function has been
called. There should be no open queries on the database connection when
this function is called, otherwise a resource leak will occur.
bool QSqlDatabase::rollback ()
Rolls a transaction back on the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature(), commit(), and transaction().
void QSqlDatabase::setConnectOptions ( const QString & options = QString::null
)
Sets the database connect options to options. See the "connectOptions"
property for details.
void QSqlDatabase::setDatabaseName ( const QString & name ) [virtual]
Sets the name of the database to name. See the "databaseName" property
for details.
void QSqlDatabase::setHostName ( const QString & host ) [virtual]
Sets the host name where the database resides to host. See the
"hostName" property for details.
void QSqlDatabase::setPassword ( const QString & password ) [virtual]
Sets the password used to connect to the database to password. See the
"password" property for details.
void QSqlDatabase::setPort ( int p ) [virtual]
Sets the port used to connect to the database to p. See the "port"
property for details.
void QSqlDatabase::setUserName ( const QString & name ) [virtual]
Sets the user name connected to the database to name. See the
"userName" property for details.
QStringList QSqlDatabase::tables ( QSql::TableType type ) const
Returns a list of the database's tables, system tables and views, as
specified by the parameter type.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myDatabase.tables( QSql::Tables | QSql::Views );
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
Example: sql/sqltable/main.cpp.
QStringList QSqlDatabase::tables () const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a list of the database's tables that are visible to the user.
To include views or system tables, use the version of this function
that takes a table type parameter.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myDatabase.tables();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
bool QSqlDatabase::transaction ()
Begins a transaction on the database if the driver supports
transactions. Returns TRUE if the operation succeeded; otherwise
returns FALSE.
See also QSqlDriver::hasFeature(), commit(), and rollback().
QString QSqlDatabase::userName () const
Returns the user name connected to the database. See the "userName"
property for details.
Property Documentation
QString connectOptions
This property holds the database connect options.
The format of the options string is a semi-colon separated list of
option names or option = value pairs. The options depend on the
database client used:
<center>.nf
</center>
Example of usage:
...
// MySQL connection
db->setConnectOptions( "CLIENT_SSL;CLIENT_IGNORE_SPACE" ); // 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
...
}
Please refer to the client library documentation for more information
about the different options. The options will be set prior to opening
the database connection. Setting new options without re-opening the
connection does nothing.
See also
Set this property's value with setConnectOptions() and get this
property's value with connectOptions().
QString databaseName
This property holds the name of the database.
Note that the database name is the TNS Service Name for the QOCI8
(Oracle) driver.
For the QODBC3 driver it can either be a DSN, a DSN filename (the file
must have a .dsn extension), or a connection string. MS Access users
can for example use the following connection string to open a .mdb file
directly, instead of having to create a DSN entry in the ODBC manager:
...
db = QSqlDatabase::addDatabase( "QODBC3" );
db->setDatabaseName( "DRIVER={Microsoft Access Driver (*.mdb)};FIL={MS Access};DBQ=myaccessfile.mdb" );
if ( db->open() ) {
// success!
}
...
("FIL" is the required spelling in Microsoft's API.)
There is no default value.
Set this property's value with setDatabaseName() and get this
property's value with databaseName().
QString hostName
This property holds the host name where the database resides.
There is no default value.
Set this property's value with setHostName() and get this property's
value with hostName().
QString password
This property holds the password used to connect to the database.
There is no default value.
Warning: This function stores the password in plain text within Qt. Use
the open() call that takes a password as parameter to avoid this
behaviour.
See also open().
Set this property's value with setPassword() and get this property's
value with password().
int port
This property holds the port used to connect to the database.
There is no default value.
Set this property's value with setPort() and get this property's value
with port().
QString userName
This property holds the user name connected to the database.
There is no default value.
Set this property's value with setUserName() and get this property's
value with userName().
SEE ALSO
http://doc.trolltech.com/qsqldatabase.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qsqldatabase.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QSqlDatabase(3qt)
