This is useful to be able to pass in mysql_limit=1 from using the
ORM.

is the flag that per :ticket:`2992` causes an order by or group by
an expression that's also in the columns clause to be copied by
label, even if referenced as the expression object.   The behavior
for MSSQL is now the old behavior that copies the whole expression
in by default, as MSSQL can be picky on these particularly in
GROUP BY expressions.
fixes #3338
- Add a test that includes a composed label in a GROUP BY

and :class:`.CheckConstraint` has been further enhanced such that
when the constraint is associated with non-table-bound :class:`.Column`
objects, the constraint will set up event listeners with the
columns themselves such that the constraint auto attaches at the
same time the columns are associated with the table.  This in particular
helps in some edge cases in declarative but is also of general use.
fixes #3341

a label that was anonymous, then labeled again with a name, would
fail to be locatable via a textual label.  This situation occurs
naturally when a mapped :func:`.column_property` is given an
explicit label in a query.
fixes #3340

operation with unicode parameters.  SQLAlchemy now passes both
the statement as well as the bound parameters as unicode
objects, as PyMySQL generally uses string interpolation
internally to produce the final statement, and in the case of
executemany does the "encode" step only on the final statement.
fixes #3337

as up-to-date recommendations as possible