Fixed bug where the multi-table support for UPDATE and DELETE statements
did not consider the additional FROM elements as targets for correlation,
when a correlated SELECT were also combined with the statement. This
change now includes that a SELECT statement in the WHERE clause for such a
statement will try to auto-correlate back to these additional tables in the
parent UPDATE/DELETE or unconditionally correlate if
:meth:`.Select.correlate` is used. Note that auto-correlation raises an
error if the SELECT statement would have no FROM clauses as a result, which
can now occur if the parent UPDATE/DELETE specifies the same tables in its
additional set of tables ; specify :meth:`.Select.correlate` explicitly to
resolve.
Change-Id: Ie11eaad7e49af3f59df11691b104d6359341bdae
Fixes: #4313
would produce an empty WHERE clause when an empty :func:`.and_()`
or :func:`.or_()` or other blank expression were applied. This is
now consistent with that of :func:`.select`.
fixes#3045
Mike Bayer