`OUT` Modifier

Although PROCEDURE does not return any value, can still make changes in variables.

sql

DELIMITER $$
CREATE OR REPLACE PROCEDURE [procedure_name]( param1 [type], OUT param2 [type])
BEGIN
    ...
END
$$
DELIMITER;

Just like in C#, declare variables outside the procedure, then pass them with OUT modifier into procedure. In the implementation of the procedure, those variables must have a new assignment. And outside the procedure, those values also change. Basically means passing reference to procedure.

CSharp

Method(250, out var b);
System.Console.WriteLine(b); // 250
static int Method(int a, out int b) => b = a;

OUT Modifier ​

`OUT` Modifier