MySQL IF ELSE 语句在表达式计算结果为 false 时实现基本条件构造。其语法如下 -
IF expression THEN
statements;
ELSE
else-statements;
END IF;
登录后复制
语句必须以分号结尾。
为了演示在 MySQL 存储过程中使用 IF ELSE 语句,我们创建了以下存储过程:基于名为“student_info”的表的值,如下所示 -
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
以下查询将创建一个名为“coursedetails_IFELSE”的过程,其中包含 IF ELSE 语句 -
mysql> DELIMITER // ;
mysql> CREATE PROCEDURE coursedetails_IFELSE(IN S_Subject Varchar(20), OUT S_Course varchar(50))
-> 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)';
-> ELSE
-> SET S_Course = 'Subject Not in the table ';
-> END IF;
-> END //
Query OK, 0 rows affected (0.00 sec)
登录后复制
现在,当我们调用这个过程时,我们可以看到下面的结果 -
mysql> Delimiter ; //
mysql> CALL coursedetails_IFELSE('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)
mysql> CALL coursedetails_IFELSE ('History', @S_Course);
Query OK, 0 rows affected (0.00 sec)
mysql> Select @S_Course;
+--------------------------------+
| @S_Course |
+--------------------------------+
| Subject Not in the table |
+--------------------------------+
1 row in set (0.00 sec)
登录后复制
以上就是MySQL IF ELSE 语句如何在存储过程中使用?的详细内容,更多请关注每日运维网(www.mryunwei.com)其它相关文章!