diff options
Diffstat (limited to 'lib/sqlalchemy/sql/util.py')
| -rw-r--r-- | lib/sqlalchemy/sql/util.py | 32 |
1 files changed, 29 insertions, 3 deletions
diff --git a/lib/sqlalchemy/sql/util.py b/lib/sqlalchemy/sql/util.py index 63067585e..fa3bae835 100644 --- a/lib/sqlalchemy/sql/util.py +++ b/lib/sqlalchemy/sql/util.py @@ -46,9 +46,35 @@ from .. import exc from .. import util -join_condition = util.langhelpers.public_factory( - Join._join_condition, ".sql.util.join_condition" -) +def join_condition(a, b, a_subset=None, consider_as_foreign_keys=None): + """Create a join condition between two tables or selectables. + + e.g.:: + + join_condition(tablea, tableb) + + would produce an expression along the lines of:: + + tablea.c.id==tableb.c.tablea_id + + The join is determined based on the foreign key relationships + between the two selectables. If there are multiple ways + to join, or no way to join, an error is raised. + + :param a_subset: An optional expression that is a sub-component + of ``a``. An attempt will be made to join to just this sub-component + first before looking at the full ``a`` construct, and if found + will be successful even if there are other ways to join to ``a``. + This allows the "right side" of a join to be passed thereby + providing a "natural join". + + """ + return Join._join_condition( + a, + b, + a_subset=a_subset, + consider_as_foreign_keys=consider_as_foreign_keys, + ) def find_join_source(clauses, join_to): |