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Classe « SelectBase »

Méthode sqlalchemy.SelectBase.subquery

Signature de la méthode subquery

def subquery(self, name: 'Optional[str]' = None) -> 'Subquery' 

Description

help(SelectBase.subquery)

Return a subquery of this :class:`_expression.SelectBase`.

A subquery is from a SQL perspective a parenthesized, named
construct that can be placed in the FROM clause of another
SELECT statement.

Given a SELECT statement such as::

    stmt = select(table.c.id, table.c.name)

The above statement might look like:

.. sourcecode:: sql

    SELECT table.id, table.name FROM table

The subquery form by itself renders the same way, however when
embedded into the FROM clause of another SELECT statement, it becomes
a named sub-element::

    subq = stmt.subquery()
    new_stmt = select(subq)

The above renders as:

.. sourcecode:: sql

    SELECT anon_1.id, anon_1.name
    FROM (SELECT table.id, table.name FROM table) AS anon_1

Historically, :meth:`_expression.SelectBase.subquery`
is equivalent to calling
the :meth:`_expression.FromClause.alias`
method on a FROM object; however,
as a :class:`_expression.SelectBase`
object is not directly  FROM object,
the :meth:`_expression.SelectBase.subquery`
method provides clearer semantics.

.. versionadded:: 1.4

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