编写 MySQL 案例语句来为学生的结果设置自定义消息
mysqlmysqli database
为此，使用 MySQL CASE 语句设置条件 −
mysql> create table DemoTable1916 ( StudentName varchar(20), StudentMarks int ); Query OK, 0 rows affected (0.00 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1916 values('Chris',59);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1916 values('David',89);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1916 values('Sam',94);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1916 values('Mike',75);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1916 values('Carol',69);
Query OK, 1 row affected (0.00 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1916;
这将产生以下输出 −
+-------------+--------------+ | StudentName | StudentMarks | +-------------+--------------+ | Chris | 59 | | David | 89 | | Sam | 94 | | Mike | 75 | | Carol | 69 | +-------------+--------------+ 5 rows in set (0.00 sec)
以下是为学生成绩设置自定义消息的查询 −
mysql> select StudentName, case when StudentMarks > 70 Then 'Good Marks' else 'Not Good Marks' end as Result from DemoTable1916;
这将产生以下输出 −
+-------------+----------------+ | StudentName | Result | +-------------+----------------+ | Chris | Not Good Marks | | David | Good Marks | | Sam | Good Marks | | Mike | Good Marks | | Carol | Not Good Marks| +-------------+----------------+ 5 rows in set (0.00 sec)
