Storage function learning notes

Creation and call of stored procedure

Function creation 1

delimiter $
CREATE FUNCTION email_byname()
RETURNS VARCHAR(25)
DETERMINISTIC
CONTAINS SQL
READS SQL DATA
BEGIN
RETURN(SELECT email FROM emp WHERE last_name = “abel”);
END $
delimiter ;

SELECT email_byname();

Function creation 2

SET GLOBAL log_bin_trust_function_creators = 1;
delimiter //
CREATE FUNCTION email_byid(emp_id INT)
RETURNS VARCHAR(15)
BEGIN
RETURN (SELECT email FROM emp WHERE employee_id = emp_id);
END //
delimiter ;
SELECT email_byid(101);

delimiter //
CREATE FUNCTION count_byid(dept_id INT)
RETURNS INT
BEGIN
	RETURN(SELECT count(*) FROM emp WHERE department_id = dept_id);
END //
delimiter ;
SET @dept_id:= 30;
SELECT count_byid(@dept_id)

 The storage function must have a return value , A stored procedure may not return a value , Stored procedures are generally used for update operations , The storage function is generally used to query that the result is a value and returns . Stored procedures can have more return values 

View of stored procedures and functions 、 modify 、 Delete

see

• show create function or procedure Function creation information
• show procedure status
• SELECT * FROM information_schema.Routines
  WHERE routine_name = ‘email_byid’; View information about stored procedures and stored functions from this table

Modification of stored procedure functions

ALTER PROCEDURE show_max_salary
SQL SECURITY invoker
COMMENT ‘ Query maximum wage ’;

show PROCEDURE STATUS like ‘show_max_salary’

The note to modify this table is to query the maximum salary
Then view the information

Deletes stored procedures and functions

DROP FUNCTION if EXISTS connt_byid

advantage ： The stored procedure is compiled when it is created , After that, it will not be compiled
The security of stored procedure is better than that of price , You can set permissions
shortcoming ： Difficult to debug and extend , There's no portability , Increasing the pressure on the database in the case of high concurrency