MySQL IF 语句如何在存储过程中使用？

MySQL IF 语句在存储过程中实现基本条件构造。其语法如下 -

IF expression THEN Statements; END IF;登录后复制

mysql> Select * from student_info; +------+---------+------------+------------+ | id   | Name    | Address    | Subject    | +------+---------+------------+------------+ | 101  | YashPal | Amritsar   | History    | | 105  | Gaurav  | Jaipur     | Literature | | 125  | Raman   | Shimla     | Computers  | +------+---------+------------+------------+ 3 rows in set (0.00 sec)登录后复制

mysql> DELIMITER // ; mysql> CREATE PROCEDURE coursedetails_IF(IN S_Subject Varchar(20), OUT S_Course varchar(20))     -> BEGIN     -> DECLARE Sub Varchar(20);     -> SELECT Subject INTO SUB     -> FROM Student_info WHERE S_Subject = Subject;     -> IF Sub = 'Computers' THEN     -> SET S_Course = 'B.Tech(CSE)';     -> END IF;     -> END // Query OK, 0 rows affected (0.00 sec)登录后复制

mysql> Delimiter ; // mysql> CALL coursedetails_IF('Computers', @S_Course); Query OK, 1 row affected (0.00 sec) mysql> Select @S_Course; +-------------+ | @S_Course   | +-------------+ | B.Tech(CSE) | +-------------+ 1 row in set (0.00 sec)登录后复制