SQL Statements and Expressions API
This section presents the API reference for the SQL Expression Language. For a full introduction to its usage, see :ref:`sqlexpression_toplevel`.
The expression package uses functions to construct SQL expressions. The return value of each function is an object instance which is a subclass of :class:`~sqlalchemy.sql.expression.ClauseElement`.
SQL functions which are known to SQLAlchemy with regards to database-specific rendering, return types and argument behavior. Generic functions are invoked like all SQL functions, using the :attr:`func` attribute:
Note that any name not known to :attr:`func` generates the function name as is - there is no restriction on what SQL functions can be called, known or unknown to SQLAlchemy, built-in or user defined. The section here only describes those functions where SQLAlchemy already knows what argument and return types are in use.