Stored procedure learning notes

function

Self defined

stored procedure

Relative to the function, there can be no return value , Stored procedure stored function is stored in mysql On the server of , And pre compiled
stored procedure ：
No parameters
Only in type （ No return with parameters ）
Only out type （ No parameters return ）
Yes in and out Parameters of type （ There are parameters and returns ）
If you don't specify it when you create it, the default is in type

stored procedure
characteristics： Indicate the constraints in the stored procedure
language sql： Indicates whether the result of the stored procedure behavior is certain
sql security： Indicate the permissions of the stored procedure

delimit $ Replace the seal to indicate the end

Creation of stored procedures

delimiter //
CREATE PROCEDURE show_max_salary()
BEGIN
SELECT MAX(salary) FROM emp;
END //
delimiter ;

Calls to stored procedures

CALL show_max_salary

Create calls with parameters in stored procedures

elimiter //
CREATE PROCEDURE show_min_salary(OUT ms DOUBLE)
BEGIN
SELECT min(salary) INTO ms
FROM emp;
END //
delimit ;

call show_min_salary(@ms);
SELECT @ms

Call of stored procedure with parameters 2

delimiter //
CREATE procedure show_some_one_salary (IN empname VARCHAR(20))
BEGIN
SELECT salary FROM emp WHERE last_name = empname;
END //
delimiter ;

Call mode 1

call show_some_one_salary(“abel”)

Call mode 2

set @empname = ‘Abel’;
call show_some_one_salary(@empname);

Creation and call of stored procedure with parameters 3

delimiter //
CREATE PROCEDURE show_someone_salary(IN empname varchar(20),OUT empsalary DECIMAL(10,2))
BEGIN 
	SELECT salary INTO empsalary FROM emp WHERE last_name = empname;
END //
delimiter ;
SET @empname = "abel";
call show_someone_salary (@empname,@empsalary);
SELECT @empsalary

stored procedure inout3

delimiter $ 
CREATE procedure show_mgr_name(inout empname VARCHAR(25)) 
BEGIN 
	SELECT last_name INTO empname FROM emp 
	WHERE employee_id =
	(SELECT manager_id FROM emp WHERE last_name = empname);
end $
delimiter ;
set @empname := "abel";
call show_mgr_name(@empname);
SELECT @empname

ps： When using stored procedures, it is difficult to troubleshoot errors because they cannot be debugged