diff options
Diffstat (limited to 'lib/sqlalchemy/sql/expression.py')
| -rw-r--r-- | lib/sqlalchemy/sql/expression.py | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py index 9a7f5e376..d5a2a5448 100644 --- a/lib/sqlalchemy/sql/expression.py +++ b/lib/sqlalchemy/sql/expression.py @@ -3318,8 +3318,9 @@ class _Exists(_UnaryExpression): return e def select_from(self, clause): - """return a new exists() construct with the given expression set as - its FROM clause. + """return a new :class:`._Exists` construct, applying the given expression + to the :meth:`.Select.select_from` method of the select statement + contained. """ e = self._clone() @@ -4677,8 +4678,16 @@ class Select(_SelectBase): @_generative def select_from(self, fromclause): - """return a new select() construct with the given FROM expression - applied to its list of FROM objects. + """return a new :class:`.Select` construct with the given FROM expression + merged into its list of FROM objects. + + The "from" list is a unique set on the identity of each element, + so adding an already present :class:`.Table` or other selectable + will have no effect. Passing a :class:`.Join` that refers + to an already present :class:`.Table` or other selectable will have + the effect of concealing the presence of that selectable as + an individual element in the rendered FROM list, instead rendering it into a + JOIN clause. """ self.append_from(fromclause) |