Question

When I make a stored procedure with SQLYog, it gives me this template:

DELIMITER $$

CREATE
    /*[DEFINER = { user | CURRENT_USER }]*/
    PROCEDURE `apachelogs`.`test`()
    /*LANGUAGE SQL
    | [NOT] DETERMINISTIC
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }
    | COMMENT 'string'*/
    BEGIN

    END$$

DELIMITER ;

I wonder why it changes delimiter before creating stored procedure. And why I can still use ; delimiter inside of create statement(I guess it may because of scope).

Answer 1

That changes the statement delimiter to $$ to keep MySQL from trying to interpret any semicolons inside the stored procedure as a delimiter. Without the DELIMITER $$, you wouldn’t be able to define a stored procedure that contained ; to delimit statements inside it. You can think of it as a way to globally escape the semicolon for the duration of the procedure’s definition.

From the fine manual:

To redefine the mysql delimiter, use the delimiter command. The following example shows how to do this for the dorepeat() procedure just shown. The delimiter is changed to // to enable the entire definition to be passed to the server as a single statement, and then restored to ; before invoking the procedure. This enables the ; delimiter used in the procedure body to be passed through to the server rather than being interpreted by mysql itself.

I don’t know if my explanation is any clearer than the manual’s but maybe one of them (or both combined) will result in some understanding.