class QSqlDatabase

The QSqlDatabase class handles a connection to a database. More…

Synopsis

Properties

Methods

Static functions

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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. A QSqlDatabase instance must only be accessed by the thread it was created in. Therefore you have to make sure to create them in the correct context. Alternatively you can change the context with moveToThread() .

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 (depending on the type of database) 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, the default connection will be assumed if you call any static member function without specifying the connection name. The following snippet shows how to create and open a default connection to a PostgreSQL database:

db = QSqlDatabase.addDatabase("QPSQL")
db.setHostName("acidalia")
db.setDatabaseName("customdb")
db.setUserName("mojito")
db.setPassword("J0a1m8")
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:

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.

Warning

It is highly recommended that you do not keep a copy of the QSqlDatabase around as a member of a class, as this will prevent the instance from being correctly cleaned up on shutdown. If you need to access an existing QSqlDatabase , it should be accessed with database() . If you chose to have a QSqlDatabase member variable, this needs to be deleted before the QCoreApplication instance is deleted, otherwise it may lead to undefined behavior.

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.

Some utility methods:

tables()

returns the list of tables

primaryIndex()

returns a table’s primary index

record()

returns meta-information about a table’s fields

transaction()

starts a transaction

commit()

saves and completes a transaction

rollback()

cancels a transaction

hasFeature()

checks if a driver supports transactions

lastError()

returns information about the last error

drivers()

returns the names of the available SQL drivers

isDriverAvailable()

checks if a particular driver is available

registerSqlDriver()

registers a custom-made driver

Note

When using transactions, you must start the transaction before you create your query.

See also

QSqlDriver QSqlQuery Qt SQL Threads and the SQL Module

Note

Properties can be used directly when from __feature__ import true_property is used or via accessor functions otherwise.

property numericalPrecisionPolicyᅟ: QSql.NumericalPrecisionPolicy

This property holds the default numerical precision policy used by queries created on this database connection.

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

Note: Setting the default precision policy to precisionPolicy doesn’t affect any currently active queries.

Access functions:
PySide6.QtSql.QSqlDatabase.defaultConnection
__init__()

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

__init__(driver)
Parameters:

driver – QSqlDriver

This is an overloaded function.

Creates a database connection using the given driver.

__init__(other)
Parameters:

other – QSqlDatabase

Creates a copy of other.

__init__(type)
Parameters:

type – str

This is an overloaded function.

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

QMIMER

Mimer SQL 11 or above

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

static addDatabase(driver[, connectionName=QLatin1StringView(QSqlDatabase.defaultConnection)])
Parameters:
Return type:

QSqlDatabase

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This is an overloaded function.

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:

con = PQconnectdb("host=server user=bart password=simpson dbname=springfield")
drv = QPSQLDriver(con)
db = QSqlDatabase.addDatabase(drv) # becomes the default() connection()
query = QSqlQuery()
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

QSQLITE

QSQLiteDriver

sqlite *connection

qsql_sqlite.cpp

QMIMER

QMimerSQLDriver

MimerSession *connection

qsql_mimer.cpp

QIBASE

QIBaseDriver

isc_db_handle connection

qsql_ibase.cpp

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()

static addDatabase(type[, connectionName=QLatin1StringView(QSqlDatabase.defaultConnection)])
Parameters:

  • type – str

  • connectionName – str

Return type:

QSqlDatabase

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() .

See also

database() removeDatabase() Threads and the SQL Module

static cloneDatabase(other, connectionName)
Parameters:
Return type:

QSqlDatabase

Clones the database connection other 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() .

static cloneDatabase(other, connectionName)
Parameters:

  • other – str

  • connectionName – str

Return type:

QSqlDatabase

This is an overloaded function.

Clones the database connection other 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() .

This overload is useful when cloning the database in another thread to the one that is used by the database represented by other.

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()
Return type:

bool

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.

connectOptions()
Return type:

str

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

connectionName()
Return type:

str

Returns the connection name, which may be empty.

Note

The connection name is not the database name .

See also

addDatabase()

static connectionNames()
Return type:

list of strings

Returns a list containing the names of all connections.

See also

contains() database() Threads and the SQL Module

static contains([connectionName=QLatin1StringView(QSqlDatabase.defaultConnection)])
Parameters:

connectionName – str

Return type:

bool

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

See also

connectionNames() database() Threads and the SQL Module

static database([connectionName=QLatin1StringView(QSqlDatabase.defaultConnection)[, open=true]])
Parameters:

  • connectionName – str

  • open – bool

Return type:

QSqlDatabase

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() Threads and the SQL Module

databaseName()
Return type:

str

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

Note

The database name is not the connection name.

See also

setDatabaseName()

driver()
Return type:

QSqlDriver

Returns the database driver used to access the database connection.

driverName()
Return type:

str

Returns the connection’s driver name.

static drivers()
Return type:

list of strings

Returns a list of all the available database drivers.

exec([query=""])
Parameters:

query – str

Return type:

QSqlQuery

Note

This function is deprecated.

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.

Use exec() instead.

exec_([query=""])
Parameters:

query – str

Return type:

QSqlQuery

hostName()
Return type:

str

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

See also

setHostName()

static isDriverAvailable(name)
Parameters:

name – str

Return type:

bool

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

See also

drivers()

isOpen()
Return type:

bool

Returns true if the database connection is currently open; otherwise returns false.

isOpenError()
Return type:

bool

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

isValid()
Return type:

bool

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Returns true if the QSqlDatabase has a valid driver.

Example:

db = QSqlDatabase()
print(db.isValid() ) # Returns false
db = QSqlDatabase.database("sales")
print(db.isValid() # Returns \c true if "sales" connection exists)
QSqlDatabase.removeDatabase("sales")
print(db.isValid() ) # Returns false
lastError()
Return type:

QSqlError

Returns information about the last error that occurred on the database.

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

moveToThread(targetThread)
Parameters:

targetThread – QThread

Return type:

bool

Changes the thread affinity for QSqlDatabase and its associated driver. This function returns true when the function succeeds. Event processing will continue in the targetThread.

During this operation you have to make sure that there is no QSqlQuery bound to this instance otherwise the QSqlDatabase will not be moved to the given thread and the function returns false.

Since the associated driver is derived from QObject, all constraints for moving a QObject to another thread also apply to this function.

See also

moveToThread()Threads and the SQL Module

numericalPrecisionPolicy()
Return type:

NumericalPrecisionPolicy

Returns the numericalPrecisionPolicy.

Getter of property numericalPrecisionPolicyᅟ .

open()
Return type:

bool

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

open(user, password)
Parameters:

  • user – str

  • password – str

Return type:

bool

This is an overloaded 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 the connection and it is then discarded.

See also

lastError()

password()
Return type:

str

Returns the connection’s password. An empty string will be returned if the password was not set with setPassword() , and if the password was given in the open() call, or if no password was used.

See also

setPassword()

port()
Return type:

int

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

See also

setPort()

primaryIndex(tablename)
Parameters:

tablename – str

Return type:

QSqlIndex

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

Note

Some drivers, such as the QPSQL driver, may may require you to pass tablename in lower case if the table was not quoted when created. See the Qt SQL driver documentation for more information.

See also

tables() record()

record(tablename)
Parameters:

tablename – str

Return type:

QSqlRecord

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.

Note

Some drivers, such as the QPSQL driver, may may require you to pass tablename in lower case if the table was not quoted when created. See the Qt SQL driver documentation for more information.

static registerSqlDriver(name, creator)
Parameters:

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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", QSqlDriverCreator()<QSqlDriver>)
QVERIFY(QSqlDatabase.drivers().contains("MYDRIVER"))
db = QSqlDatabase.addDatabase("MYDRIVER")
QVERIFY(db.isValid())

QSqlDatabase takes ownership of the creator pointer, so you mustn’t delete it yourself.

See also

drivers()

static removeDatabase(connectionName)
Parameters:

connectionName – str

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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
db = QSqlDatabase.database("sales")
query = 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:

    db = QSqlDatabase.database("sales")
    query = 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() Threads and the SQL Module

rollback()
Return type:

bool

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.

setConnectOptions([options=""])
Parameters:

options – str

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Sets database-specific options. This must be done before the connection is opened, otherwise it has no effect. Another possibility is to close the connection, call QSqlDatabase::setConnectOptions(), 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 and are described for each plugin in the SQL Database Drivers page.

Examples:

db.setConnectOptions("SSL_KEY=client-key.pemSSL_CERT=client-cert.pem;SSL_CA=ca-cert.pem;CLIENT_IGNORE_SPACE=1"); # use an SSL connection to the server
if not db.open():
    db.setConnectOptions() # clears the connect option string
    # ...

# ...
# PostgreSQL connection
db.setConnectOptions("requiressl=1") # enable PostgreSQL SSL connections
if not db.open():
    db.setConnectOptions() # clear options
    # ...

# ...
# ODBC connection
db.setConnectOptions("SQL_ATTR_ACCESS_MODE=SQL_MODE_READ_ONLYSQL_ATTR_TRACE=SQL_OPT_TRACE_ON"); # set ODBC options
if not 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(name)
Parameters:

name – str

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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 QSQLITE driver, if the database name specified does not exist, then it will create the file for you unless the QSQLITE_OPEN_READONLY option is set.

Additionally, name can be set to ":memory:" which will create a temporary database which is only available for the lifetime of the application.

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, *.accdb)};FIL={MS Access};DBQ=myaccessfile.mdb")
if db.open():
    # success!

# ...

There is no default value.

setHostName(host)
Parameters:

host – str

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.

setNumericalPrecisionPolicy(precisionPolicy)
Parameters:

precisionPolicy – NumericalPrecisionPolicy

Sets numericalPrecisionPolicy to precisionPolicy.

Setter of property numericalPrecisionPolicyᅟ .

setPassword(password)
Parameters:

password – str

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() open()

setPort(p)
Parameters:

p – int

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.

setUserName(name)
Parameters:

name – str

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.

tables([type=QSql.Tables])
Parameters:

type – TableType

Return type:

list of strings

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

thread()
Return type:

QThread

Returns a pointer to the associated QThread instance.

transaction()
Return type:

bool

Begins a transaction on the database if the driver supports transactions. Returns true if the operation succeeded. Otherwise it returns false.

userName()
Return type:

str

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

See also

setUserName()