Syntax options: DETERMINISTIC | NOT DETERMINISTIC The clause controls the evaluation of an external function in the scope of a query: o NOT DETERMINISTIC Specifying the NOT DETERMINISTIC clause forces evaluation of corresponding functions (in scope of a single query) every time the function appears. If a function can return a different result each time it is invoked, you should use the DETERMINISTIC clause. o DETERMINISTIC Specifying the DETERMINISTIC clause can result in a single evaluation of corresponding function expressions (in scope of a single query), and the resulting value is used in all occurrences of the corresponding function expression. When you use the DETERMINISTIC clause, Oracle Rdb evaluates whether or not to invoke the function each time it is used. For example: SELECT * FROM T1 WHERE F1() > 0 AND F1() < 20; If you define the F1 function as DETERMINISTIC, the function F1() may be evaluated just once depending on the optimizer. If you define the F1 function as NOT DETERMINISTIC, the function F1() is evaluated twice. DETERMINISTIC is the default. The DETERMINISTIC or NOT DETERMINISTIC clause is not allowed on procedure definitions.