SQL中创建存储过程

创建SQL存储过程需要使用到的语法

- 创建存储过程

CREATE 存储过程的名称(参数)
BEGIN
...需要执行的SQL语句
END

- 调用

CALL 存储过程的名称(参数)

个人看法，这就是一个函数...

无参数

CREATE PROCEDURE p_student_select()
BEGIN
SELECT * FROM student;
END

CALL p_student_select()

带参

# out其实就是cpp里的引用变量，in就是值传递
CREATE PROCEDURE p_count(OUT count int)
BEGIN
SELECT COUNT(*) into count FROM student;
END

set @num = 10;# 定义变量
CALL p_count(@num);#我的数据有11条
SELECT @num as num;#这里的num已经是11了

--这个就是一个调用参数的函数
CREATE PROCEDURE p_studnt_selectById(in id int)
BEGIN
SELECT * FROM student WHERE studentNo = id;
END

CALL p_studnt_selectById(4)

两个参数

#两个参数是一样的用法
CREATE PROCEDURE p_result_test(out num int, in id int)
BEGIN
SELECT COUNT(*) INTO num FROM result WHERE studentNo = id;
END

set @num = 0;
CALL p_result_test(@num, 3);
SELECT @num as num

declare关键字的使用

# declare的作用是用来定义变量

CREATE PROCEDURE p5()
BEGIN
DECLARE studentName VARCHAR(10);#创建了一个变量
set @studentName = 'HELLO';#给变量赋值
END

CALL p5();
SELECT @studentName
-- 说明了declare定义的变量可以在外部直接调用

IF语句

#if语句没啥说的，代码直接能看懂
CREATE PROCEDURE p6(in id int)
BEGIN
IF(id = 0) THEN
SELECT * FROM student;
ELSE
SELECT * FROM teacher;
END IF;
END

case语句

#看代码...
CREATE PROCEDURE p7(in tab VARCHAR(10))
BEGIN
CASE tab
WHEN 'student' THEN
SELECT * FROM student;
WHEN 'teacher' THEN
SELECT * FROM teacher;
END CASE;
END

loop语句

CREATE PROCEDURE p9(IN id INT)
BEGIN
addloop: LOOP
set id = id + 1;
SELECT id;
IF id > 10 THEN
LEAVE addloop;
ELSE
SELECT * FROM student;
END IF;
END LOOP addloop;

END

repeat

CREATE PROCEDURE p10(in count int)
BEGIN
REPEAT
set count = count + 1;
SELECT count;
UNTIL count > 10 END REPEAT;#count >10跳出

END

while

CREATE PROCEDURE p11(in num int)
BEGIN
while num < 10 DO
SELECT num;
SET  num = num + 1;
END WHILE;
END

来源：https://blog.csdn.net/ht_vIC/article/details/121372997