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

Synopsis¶
Functions¶
def
close
()def
commit
()def
connectOptions
()def
connectionName
()def
databaseName
()def
driver
()def
driverName
()def
exec
([query=””])def
exec_
([query=””])def
hostName
()def
isOpen
()def
isOpenError
()def
isValid
()def
lastError
()def
numericalPrecisionPolicy
()def
open
()def
open
(user, password)def
password
()def
port
()def
primaryIndex
(tablename)def
record
(tablename)def
rollback
()def
setConnectOptions
([options=””])def
setDatabaseName
(name)def
setHostName
(host)def
setNumericalPrecisionPolicy
(precisionPolicy)def
setPassword
(password)def
setPort
(p)def
setUserName
(name)def
tables
([type=QSql.Tables])def
transaction
()def
userName
()
Static functions¶
def
addDatabase
(driver[, connectionName=QLatin1String(QSqlDatabase.defaultConnection)])def
addDatabase
(type[, connectionName=QLatin1String(QSqlDatabase.defaultConnection)])def
cloneDatabase
(other, connectionName)def
cloneDatabase
(other, connectionName)def
connectionNames
()def
contains
([connectionName=QLatin1String(QSqlDatabase.defaultConnection)])def
database
([connectionName=QLatin1String(QSqlDatabase.defaultConnection)[, open=true]])def
drivers
()def
isDriverAvailable
(name)def
registerSqlDriver
(name, creator)def
removeDatabase
(connectionName)
Detailed Description¶
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 (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:
returns the list of tables
returns a table’s primary index
returns meta-information about a table’s fields
starts a transaction
saves and completes a transaction
cancels a transaction
hasFeature()
checks if a driver supports transactions
returns information about the last error
returns the names of the available SQL drivers
checks if a particular driver is available
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
- class PySide6.QtSql.QSqlDatabase¶
PySide6.QtSql.QSqlDatabase(driver)
PySide6.QtSql.QSqlDatabase(other)
PySide6.QtSql.QSqlDatabase(type)
- Parameters
other –
PySide6.QtSql.QSqlDatabase
driver –
PySide6.QtSql.QSqlDriver
type – str
Creates an empty, invalid QSqlDatabase
object. Use addDatabase()
, removeDatabase()
, and database()
to get valid QSqlDatabase
objects.
This is an overloaded function.
Creates a database connection using the given driver
.
- PySide6.QtSql.QSqlDatabase.defaultConnection¶
- static PySide6.QtSql.QSqlDatabase.addDatabase(driver[, connectionName=QLatin1String(QSqlDatabase.defaultConnection)])¶
- Parameters
driver –
PySide6.QtSql.QSqlDriver
connectionName – str
- Return type
- static PySide6.QtSql.QSqlDatabase.addDatabase(type[, connectionName=QLatin1String(QSqlDatabase.defaultConnection)])
- Parameters
type – str
connectionName – str
- Return type
- static PySide6.QtSql.QSqlDatabase.cloneDatabase(other, connectionName)¶
- Parameters
other –
PySide6.QtSql.QSqlDatabase
connectionName – str
- Return type
- static PySide6.QtSql.QSqlDatabase.cloneDatabase(other, connectionName)
- Parameters
other – str
connectionName – str
- Return type
- PySide6.QtSql.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
- PySide6.QtSql.QSqlDatabase.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.
See also
- PySide6.QtSql.QSqlDatabase.connectOptions()¶
- Return type
str
Returns the connection options string used for this connection. The string may be empty.
See also
- PySide6.QtSql.QSqlDatabase.connectionName()¶
- Return type
str
Returns the connection name, which may be empty.
- static PySide6.QtSql.QSqlDatabase.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 PySide6.QtSql.QSqlDatabase.contains([connectionName=QLatin1String(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 PySide6.QtSql.QSqlDatabase.database([connectionName=QLatin1String(QSqlDatabase.defaultConnection)[, open=true]])¶
- Parameters
connectionName – str
open – bool
- Return type
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
- PySide6.QtSql.QSqlDatabase.databaseName()¶
- Return type
str
Returns the connection’s database name, which may be empty.
- PySide6.QtSql.QSqlDatabase.driver()¶
- Return type
Returns the database driver used to access the database connection.
See also
- PySide6.QtSql.QSqlDatabase.driverName()¶
- Return type
str
Returns the connection’s driver name.
See also
- static PySide6.QtSql.QSqlDatabase.drivers()¶
- Return type
list of strings
Returns a list of all the available database drivers.
See also
- PySide6.QtSql.QSqlDatabase.exec([query=""])¶
- Parameters
query – str
- Return type
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
- PySide6.QtSql.QSqlDatabase.exec_([query=""])¶
- Parameters
query – str
- Return type
- PySide6.QtSql.QSqlDatabase.hostName()¶
- Return type
str
Returns the connection’s host name; it may be empty.
See also
- static PySide6.QtSql.QSqlDatabase.isDriverAvailable(name)¶
- Parameters
name – str
- Return type
bool
Returns true
if a driver called name
is available; otherwise returns false
.
See also
- PySide6.QtSql.QSqlDatabase.isOpen()¶
- Return type
bool
Returns true
if the database connection is currently open; otherwise returns false
.
- PySide6.QtSql.QSqlDatabase.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.
- PySide6.QtSql.QSqlDatabase.isValid()¶
- Return type
bool
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
- PySide6.QtSql.QSqlDatabase.lastError()¶
- Return type
Returns information about the last error that occurred on the database.
Failures that occur in conjunction with an individual query are reported by lastError()
.
See also
- PySide6.QtSql.QSqlDatabase.numericalPrecisionPolicy()¶
- Return type
Returns the current default precision policy for the database connection.
See also
NumericalPrecisionPolicy
setNumericalPrecisionPolicy()
numericalPrecisionPolicy()
setNumericalPrecisionPolicy()
- PySide6.QtSql.QSqlDatabase.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()
.
- PySide6.QtSql.QSqlDatabase.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
- PySide6.QtSql.QSqlDatabase.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
- PySide6.QtSql.QSqlDatabase.port()¶
- Return type
int
Returns the connection’s port number. The value is undefined if the port number has not been set.
See also
- PySide6.QtSql.QSqlDatabase.primaryIndex(tablename)¶
- Parameters
tablename – str
- Return type
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.
- PySide6.QtSql.QSqlDatabase.record(tablename)¶
- Parameters
tablename – str
- Return type
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 PySide6.QtSql.QSqlDatabase.registerSqlDriver(name, creator)¶
- Parameters
name – str
creator –
PySide6.QtSql.QSqlDriverCreatorBase
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
- static PySide6.QtSql.QSqlDatabase.removeDatabase(connectionName)¶
- Parameters
connectionName – str
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
- PySide6.QtSql.QSqlDatabase.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.
See also
- PySide6.QtSql.QSqlDatabase.setConnectOptions([options=""])¶
- Parameters
options – str
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 , 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:
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
- PySide6.QtSql.QSqlDatabase.setDatabaseName(name)¶
- Parameters
name – str
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.
- PySide6.QtSql.QSqlDatabase.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.
- PySide6.QtSql.QSqlDatabase.setNumericalPrecisionPolicy(precisionPolicy)¶
- Parameters
precisionPolicy –
NumericalPrecisionPolicy
Sets the default numerical precision policy used by queries created on this database connection to precisionPolicy
.
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.
See also
NumericalPrecisionPolicy
numericalPrecisionPolicy()
setNumericalPrecisionPolicy()
numericalPrecisionPolicy()
- PySide6.QtSql.QSqlDatabase.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.
- PySide6.QtSql.QSqlDatabase.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.
- PySide6.QtSql.QSqlDatabase.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.
- PySide6.QtSql.QSqlDatabase.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
.
See also
- PySide6.QtSql.QSqlDatabase.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
.
See also
- PySide6.QtSql.QSqlDatabase.userName()¶
- Return type
str
Returns the connection’s user name; it may be empty.
See also
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