MySQL 根据第三个字段的值从两个字段中选择一个字段?
mysqlmysqli database
为此，使用 IF()。让我们首先创建一个表 −
mysql> create table DemoTable -> ( -> PlayerName varchar(100), -> PlayerScore int, -> PlayerStatus varchar(100) -> ); Query OK, 0 rows affected (0.58 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable values('John',88,'BAD');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('Chris',78,'BAD');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('Robert',90,'BAD');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values('David',80,'BAD');
Query OK, 1 row affected (0.23 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
输出
+------------+-------------+--------------+ | PlayerName | PlayerScore | PlayerStatus | +------------+-------------+--------------+ | John | 88 | BAD | | Chris | 78 | BAD | | Robert | 90 | BAD | | David | 80 | BAD | +------------+-------------+--------------+ 4 rows in set (0.00 sec)
以下查询根据第三个字段的值从两个字段中选择任意一个字段 −
mysql> select PlayerScore,if(PlayerScore > 80 , PlayerName ,PlayerStatus) AS Result from DemoTable;
输出
+-------------+--------+ | PlayerScore | Result | +-------------+--------+ | 88 | John | | 78 | BAD | | 90 | Robert | | 80 | BAD | +-------------+--------+ 4 rows in set (0.00 sec)
