class QSqlDriver#

The QSqlDriver class is an abstract base class for accessing specific SQL databases. More…

Inheritance diagram of PySide6.QtSql.QSqlDriver

Synopsis#

Methods#

Virtual methods#

Signals#

Note

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Detailed Description#

This class should not be used directly. Use QSqlDatabase instead.

If you want to create your own SQL drivers, you can subclass this class and reimplement its pure virtual functions and those virtual functions that you need. See How to Write Your Own Database Driver for more information.

class DriverFeature#

This enum contains a list of features a driver might support. Use hasFeature() to query whether a feature is supported or not.

Constant

Description

QSqlDriver.Transactions

Whether the driver supports SQL transactions.

QSqlDriver.QuerySize

Whether the database is capable of reporting the size of a query. Note that some databases do not support returning the size (i.e. number of rows returned) of a query, in which case size() will return -1.

QSqlDriver.BLOB

Whether the driver supports Binary Large Object fields.

QSqlDriver.Unicode

Whether the driver supports Unicode strings if the database server does.

QSqlDriver.PreparedQueries

Whether the driver supports prepared query execution.

QSqlDriver.NamedPlaceholders

Whether the driver supports the use of named placeholders.

QSqlDriver.PositionalPlaceholders

Whether the driver supports the use of positional placeholders.

QSqlDriver.LastInsertId

Whether the driver supports returning the Id of the last touched row.

QSqlDriver.BatchOperations

Whether the driver supports batched operations, see execBatch()

QSqlDriver.SimpleLocking

Whether the driver disallows a write lock on a table while other queries have a read lock on it.

QSqlDriver.LowPrecisionNumbers

Whether the driver allows fetching numerical values with low precision.

QSqlDriver.EventNotifications

Whether the driver supports database event notifications.

QSqlDriver.FinishQuery

Whether the driver can do any low-level resource cleanup when finish() is called.

QSqlDriver.MultipleResultSets

Whether the driver can access multiple result sets returned from batched statements or stored procedures.

QSqlDriver.CancelQuery

Whether the driver allows cancelling a running query.

More information about supported features can be found in the Qt SQL driver documentation.

See also

hasFeature()

class StatementType#

This enum contains a list of SQL statement (or clause) types the driver can create.

Constant

Description

QSqlDriver.WhereStatement

An SQL WHERE statement (e.g., WHERE f = 5).

QSqlDriver.SelectStatement

An SQL SELECT statement (e.g., SELECT f FROM t).

QSqlDriver.UpdateStatement

An SQL UPDATE statement (e.g., UPDATE TABLE t set f = 1).

QSqlDriver.InsertStatement

An SQL INSERT statement (e.g., INSERT INTO t (f) values (1)).

QSqlDriver.DeleteStatement

An SQL DELETE statement (e.g., DELETE FROM t).

See also

sqlStatement()

class IdentifierType#

This enum contains a list of SQL identifier types.

Constant

Description

QSqlDriver.FieldName

A SQL field name

QSqlDriver.TableName

A SQL table name
class NotificationSource#

This enum contains a list of SQL notification sources.

Constant

Description

QSqlDriver.UnknownSource

The notification source is unknown

QSqlDriver.SelfSource

The notification source is this connection

QSqlDriver.OtherSource

The notification source is another connection
class DbmsType#
__init__([parent=None])#
Parameters:

parent – QObject

Constructs a new driver with the given parent.

beginTransaction()#
Return type:

bool

This function is called to begin a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false.

cancelQuery()#
Return type:

bool

abstract close()#

Derived classes must reimplement this pure virtual function in order to close the database connection. Return true on success, false on failure.

See also

open() setOpen()

commitTransaction()#
Return type:

bool

This function is called to commit a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false.

abstract createResult()#
Return type:

QSqlResult

Creates an empty SQL result on the database. Derived classes must reimplement this function and return a QSqlResult object appropriate for their database to the caller.

dbmsType()#
Return type:

DbmsType

escapeIdentifier(identifier, type)#
Parameters:
Return type:

str

Returns the identifier escaped according to the database rules. identifier can either be a table name or field name, dependent on type.

The default implementation does nothing.

formatValue(field[, trimStrings=false])#
Parameters:
Return type:

str

Returns a string representation of the field value for the database. This is used, for example, when constructing INSERT and UPDATE statements.

The default implementation returns the value formatted as a string according to the following rules:

  • If field is character data, the value is returned enclosed in single quotation marks, which is appropriate for many SQL databases. Any embedded single-quote characters are escaped (replaced with two single-quote characters). If trimStrings is true (the default is false), all trailing whitespace is trimmed from the field.

  • If field is date/time data, the value is formatted in ISO format and enclosed in single quotation marks. If the date/time data is invalid, “NULL” is returned.

  • If field is bytearray data, and the driver can edit binary fields, the value is formatted as a hexadecimal string.

  • For any other field type, toString() is called on its value and the result of this is returned.

See also

toString()

abstract hasFeature(f)#
Parameters:

f – DriverFeature

Return type:

bool

Returns true if the driver supports feature feature; otherwise returns false.

Note that some databases need to be open() before this can be determined.

See also

DriverFeature

isIdentifierEscaped(identifier, type)#
Parameters:
Return type:

bool

Returns whether identifier is escaped according to the database rules. identifier can either be a table name or field name, dependent on type.

Reimplement this function if you want to provide your own implementation in your QSqlDriver subclass,

isOpen()#
Return type:

bool

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

isOpenError()#
Return type:

bool

Returns true if the there was an error opening the database connection; otherwise returns false.

lastError()#
Return type:

QSqlError

Returns a QSqlError object which contains information about the last error that occurred on the database.

See also

setLastError()

maximumIdentifierLength(type)#
Parameters:

type – IdentifierType

Return type:

int

Returns the maximum length for the identifier type according to the database settings. Returns INT_MAX by default if the is no maximum for the database.

notification(name, source, payload)#
Parameters:

This signal is emitted when the database posts an event notification that the driver subscribes to. name identifies the event notification, source indicates the signal source, payload holds the extra data optionally delivered with the notification.

numericalPrecisionPolicy()#
Return type:

NumericalPrecisionPolicy

Returns the current default precision policy for the database connection.

abstract open(db[, user=""[, password=""[, host=""[, port=-1[, connOpts=""]]]]])#
Parameters:

  • db – str

  • user – str

  • password – str

  • host – str

  • port – int

  • connOpts – str

Return type:

bool

Derived classes must reimplement this pure virtual function to open a database connection on database db, using user name user, password password, host host, port port and connection options options.

The function must return true on success and false on failure.

See also

setOpen()

primaryIndex(tableName)#
Parameters:

tableName – str

Return type:

QSqlIndex

Returns the primary index for table tableName. Returns an empty QSqlIndex if the table doesn’t have a primary index. The default implementation returns an empty index.

record(tableName)#
Parameters:

tableName – str

Return type:

QSqlRecord

Returns a QSqlRecord populated with the names of the fields in table tableName. If no such table exists, an empty record is returned. The default implementation returns an empty record.

rollbackTransaction()#
Return type:

bool

This function is called to rollback a transaction. If successful, return true, otherwise return false. The default implementation does nothing and returns false.

setLastError(e)#
Parameters:

e – QSqlError

This function is used to set the value of the last error, error, that occurred on the database.

See also

lastError()

setNumericalPrecisionPolicy(precisionPolicy)#
Parameters:

precisionPolicy – NumericalPrecisionPolicy

Sets the default numerical precision policy used by queries created by this driver to precisionPolicy.

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

setOpen(o)#
Parameters:

o – bool

This function sets the open state of the database to open. Derived classes can use this function to report the status of open() .

setOpenError(e)#
Parameters:

e – bool

This function sets the open error state of the database to error. Derived classes can use this function to report the status of open() . Note that if error is true the open state of the database is set to closed (i.e., isOpen() returns false).

sqlStatement(type, tableName, rec, preparedStatement)#
Parameters:
Return type:

str

Returns a SQL statement of type type for the table tableName with the values from rec. If preparedStatement is true, the string will contain placeholders instead of values.

The generated flag in each field of rec determines whether the field is included in the generated statement.

This method can be used to manipulate tables without having to worry about database-dependent SQL dialects. For non-prepared statements, the values will be properly escaped.

In the WHERE statement, each non-null field of rec specifies a filter condition of equality to the field value, or if prepared, a placeholder. However, prepared or not, a null field specifies the condition IS NULL and never introduces a placeholder. The application must not attempt to bind data for the null field during execution. The field must be set to some non-null value if a placeholder is desired. Furthermore, since non-null fields specify equality conditions and SQL NULL is not equal to anything, even itself, it is generally not useful to bind a null to a placeholder.

stripDelimiters(identifier, type)#
Parameters:
Return type:

str

Returns the identifier with the leading and trailing delimiters removed, identifier can either be a table name or field name, dependent on type. If identifier does not have leading and trailing delimiter characters, identifier is returned without modification.

Reimplement this function if you want to provide your own implementation in your QSqlDriver subclass,

subscribeToNotification(name)#
Parameters:

name – str

Return type:

bool

This function is called to subscribe to event notifications from the database. name identifies the event notification.

If successful, return true, otherwise return false.

The database must be open when this function is called. When the database is closed by calling close() all subscribed event notifications are automatically unsubscribed. Note that calling open() on an already open database may implicitly cause close() to be called, which will cause the driver to unsubscribe from all event notifications.

When an event notification identified by name is posted by the database the notification() signal is emitted.

Reimplement this function if you want to provide event notification support in your own QSqlDriver subclass,

subscribedToNotifications()#
Return type:

list of strings

Returns a list of the names of the event notifications that are currently subscribed to.

Reimplement this function if you want to provide event notification support in your own QSqlDriver subclass,

tables(tableType)#
Parameters:

tableType – TableType

Return type:

list of strings

Returns a list of the names of the tables in the database. The default implementation returns an empty list.

The tableType argument describes what types of tables should be returned. Due to binary compatibility, the string contains the value of the enum QSql::TableTypes as text. An empty string should be treated as Tables for backward compatibility.

unsubscribeFromNotification(name)#
Parameters:

name – str

Return type:

bool

This function is called to unsubscribe from event notifications from the database. name identifies the event notification.

If successful, return true, otherwise return false.

The database must be open when this function is called. All subscribed event notifications are automatically unsubscribed from when the close() function is called.

After calling this function the notification() signal will no longer be emitted when an event notification identified by name is posted by the database.

Reimplement this function if you want to provide event notification support in your own QSqlDriver subclass,