存储过程(mysql 难懂)

|-----什么是存储过程？

简单的说，就是一组SQL语句集，功能强大，可以实现一些比较复杂的逻辑功能，类似于JAVA语言中的方法；

函数的普遍特性：模块化，封装，代码复用

|----语法结构

DELIMITER ;;

DELIMITER ;

DELIMITER ;;

CREATE PROCEDURE ups_pro1(IN a INT,IN b INT,OUT SUM INT)

BEGIN

IF a IS NULL THEN SET a=0;

END IF;

IF b IS NULL THEN SET b=10;

END IF;

#赋值

SET SUM=a+b;

END

;;

DELIMITER ;

|---调用 call 调用存储过程

#@s 就不需要定义，直接调用

#调用存储过程用call

SET @b=5;

CALL ups_pro1(2,@b,@s);

SELECT @s AS SUM;

|------@变量：接收存储过程的一个变量，这个变量是不需要定义！

|----select 字段 into(给)变量 from 表名;

#思考：如果调用数据表

DELIMITER ;;

CREATE PROCEDURE ups_test_02(IN id INT,OUT question_r VARCHAR(500))

BEGIN

SELECT question INTO question_r FROM questioninfo WHERE questionid=id;

END

;;

DELIMITER ;

CALL ups_test_02(1,@str);

SELECT @str AS 题干;

|---if then elseif then else end if;

DELIMITER ;;

CREATE PROCEDURE ups_pro2(IN tt INT)

BEGIN

DECLARE c VARCHAR(200);

IF tt=0 THEN SET c='this is param is 0';

ELSEIF tt=1 THEN SET c='this is param is 1';

ELSE SET c='this is param not know';

END IF;

SELECT c;

END

;;

DELIMITER ;

CALL ups_pro2(1);

DELIMITER ;;

CREATE PROCEDURE ups_test_05(IN id INT)

BEGIN

DECLARE name_o VARCHAR(200);#定义的变量

IF(id=1) THEN

SELECT question INTO name_o FROM questioninfo WHERE questionid=id;

ELSEIF(id=2) THEN

SELECT question INTO name_o FROM questioninfo WHERE questionid=id;

ELSE

SET name_o='不知道！';

END IF;

SELECT name_o;

END

;;

DELIMITER ;

DELIMITER ;;

CREATE PROCEDURE ups_pro3(IN tt INT)

BEGIN

DECLARE c VARCHAR(200);

CASE WHEN tt=0 THEN SET c='this is param is 0';

WHEN tt=1 THEN SET c='this is param is 1';

ELSE SET c='this is param not know';

END CASE;

SELECT c;

END

;;

DELIMITER ;

CALL ups_pro3(100);

|----while循环

DELIMITER ;;

CREATE PROCEDURE ups_pro4(IN tt INT)

BEGIN

DECLARE SUM INT;

DECLARE i INT;

SET SUM=0;

SET i=0;

WHILE i<tt DO

SET SUM=SUM+i;

SET i=i+1;

END WHILE;

SELECT SUM;

END

;;

DELIMITER ;

存储过程(mysql 难懂)

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