Entity SQL supports calling user-defined functions in a query. You can define these functions inline with the query (see How to: Call a User-Defined Function) or as part of the conceptual model (see How to: Define Custom Functions in the Conceptual Model). Conceptual model functions are defined as an Entity SQL command in the DefiningExpression element of a Function element in the conceptual model.
Entity SQL enables you to define functions in the query command itself. The FUNCTION operator defines inline functions. You can define multiple functions in a single command, and these functions can have the same function name, as long as the function signatures are unique. For more information, see Function Overload Resolution.