Allow delete where clause to refer multiple tables.

Implemented "DELETE..FROM" syntax for Postgresql, MySQL, MS SQL Server
(as well as within the unsupported Sybase dialect) in a manner similar
to how "UPDATE..FROM" works.  A DELETE statement that refers to more than
one table will switch into "multi-table" mode and render the appropriate
"USING" or multi-table "FROM" clause as understood by the database.
Pull request courtesy Pieter Mulder.

For SQL syntaxes see:

Postgresql: https://www.postgresql.org/docs/current/static/sql-delete.html
MySQL: https://dev.mysql.com/doc/refman/5.7/en/delete.html#multiple-table_syntax
MSSQL: https://docs.microsoft.com/en-us/sql/t-sql/statements/delete-transact-sql
Sybase: http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc00801.1510/html/iqrefso/X315721.htm

Co-authored by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: I6dfd57b49e44a095d076dc493cd2360bb5d920d3
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/392
Fixes: #959

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index a66b091aa..0b89a4506 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -693,6 +693,11 @@ class SuiteRequirements(Requirements):
         return exclusions.closed()
 
     @property
+    def delete_from(self):
+        """Target must support DELETE FROM..FROM or DELETE..USING syntax"""
+        return exclusions.closed()
+
+    @property
     def update_where_target_in_subquery(self):
         """Target must support UPDATE where the same table is present in a
         subquery in the WHERE clause.