QSqlRelationalTableModel¶
The
QSqlRelationalTableModel
class provides an editable data model for a single database table, with foreign key support. More…
Synopsis¶
Functions¶
def
relation
(column)def
setJoinMode
(joinMode)
Virtual functions¶
def
relationModel
(column)def
setRelation
(column, relation)
Detailed Description¶
QSqlRelationalTableModel
acts likeQSqlTableModel
, but allows columns to be set as foreign keys into other database tables.
The screenshot on the left shows a plain
QSqlTableModel
in aQTableView
. Foreign keys (city
andcountry
) aren’t resolved to human-readable values. The screenshot on the right shows aQSqlRelationalTableModel
, with foreign keys resolved into human-readable text strings.The following code snippet shows how the
QSqlRelationalTableModel
was set up:model.setTable("employee") model.setRelation(2, QSqlRelation("city", "id", "name")) model.setRelation(3, QSqlRelation("country", "id", "name"))The
setRelation()
function calls establish a relationship between two tables. The first call specifies that column 2 in tableemployee
is a foreign key that maps with fieldid
of tablecity
, and that the view should present thecity
‘sname
field to the user. The second call does something similar with column 3.If you use a read-write
QSqlRelationalTableModel
, you probably want to useQSqlRelationalDelegate
on the view. Unlike the default delegate,QSqlRelationalDelegate
provides a combobox for fields that are foreign keys into other tables. To use the class, simply callsetItemDelegate()
on the view with an instance ofQSqlRelationalDelegate
:view = QTableView() view.setModel(model) view.setItemDelegate(QSqlRelationalDelegate(view))The relationaltablemodel example illustrates how to use
QSqlRelationalTableModel
in conjunction withQSqlRelationalDelegate
to provide tables with foreign key support.Notes:
The table must have a primary key declared.
The table’s primary key may not contain a relation to another table.
If a relational table contains keys that refer to non-existent rows in the referenced table, the rows containing the invalid keys will not be exposed through the model. The user or the database is responsible for keeping referential integrity.
If a relation’s display column name is also used as a column name in the relational table, or if it is used as display column name in more than one relation it will be aliased. The alias is the relation’s table name, display column name and a unique id joined by an underscore (e.g. tablename_columnname_id).
fieldName()
will return the aliased column name. All occurrences of the duplicate display column name are aliased when duplication is detected, but no aliasing is done to the column names in the main table. The aliasing doesn’t affectQSqlRelation
, sodisplayColumn()
will return the original display column name.The reference table name is aliased. The alias is the word “relTblAl” and the relationed column index joined by an underscore (e.g. relTblAl_2). The alias can be used to filter the table (For example,
setFilter
(“relTblAl_2=’Oslo’ OR relTblAl_3=’USA’”)).When using
setData()
the role should always beEditRole
, and when usingdata()
the role should always beDisplayRole
.See also
QSqlRelation
QSqlRelationalDelegate
Relational Table Model Example
- class PySide2.QtSql.QSqlRelationalTableModel([parent=None[, db=QSqlDatabase()]])¶
- param parent:
- param db:
Creates an empty
QSqlRelationalTableModel
and sets the parent toparent
and the database connection todb
. Ifdb
is not valid, the default database connection will be used.
- PySide2.QtSql.QSqlRelationalTableModel.JoinMode¶
Constant
Description
QSqlRelationalTableModel.InnerJoin
Inner join mode, return rows when there is at least one match in both tables.
QSqlRelationalTableModel.LeftJoin
Left join mode, returns all rows from the left table (table_name1), even if there are no matches in the right table (table_name2).
See also
- PySide2.QtSql.QSqlRelationalTableModel.relation(column)¶
- Parameters:
column – int
- Return type:
Returns the relation for the column
column
, or an invalid relation if no relation is set.See also
- PySide2.QtSql.QSqlRelationalTableModel.relationModel(column)¶
- Parameters:
column – int
- Return type:
Returns a
QSqlTableModel
object for accessing the table for whichcolumn
is a foreign key, orNone
if there is no relation for the givencolumn
.The returned object is owned by the
QSqlRelationalTableModel
.See also
- PySide2.QtSql.QSqlRelationalTableModel.setJoinMode(joinMode)¶
- Parameters:
joinMode –
JoinMode
Sets the SQL
joinMode
to show or hide rows with NULL foreign keys. InInnerJoin
mode (the default) these rows will not be shown: use theLeftJoin
mode if you want to show them.See also
JoinMode
- PySide2.QtSql.QSqlRelationalTableModel.setRelation(column, relation)¶
- Parameters:
column – int
relation –
PySide2.QtSql.QSqlRelation
Lets the specified
column
be a foreign index specified byrelation
.Example:
model.setTable("employee") model.setRelation(2, QSqlRelation("city", "id", "name"))
The call specifies that column 2 in table
employee
is a foreign key that maps with fieldid
of tablecity
, and that the view should present thecity
‘sname
field to the user.Note: The table’s primary key may not contain a relation to another table.
See also
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