IF() 函数在 MySQL Select 语句中？

IF() 函数会根据某条件返回一个值。

语法如下−

SELECT IF(yourCondition, yourMessageIfConditionBecomesTrue,yourMessageIfConditionBecomesFalse) from yourTableName;
Let us first create a table:
mysql> create table DemoTable
   (
   Value int
   );
Query OK, 0 rows affected (0.60 sec)

使用 insert 命令在表中插入记录 −

mysql> insert into DemoTable values(1000);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(2000);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(500);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values(1100);
Query OK, 1 row affected (0.16 sec)

使用 select 语句从表中显示所有记录 −

mysql> select *from DemoTable;

这会产生以下输出 −

+-------+
| Value |
+-------+
| 1000  |
| 2000  |
| 500   |
| 1100  |
+-------+
4 rows in set (0.00 sec)

可以在 MySQL 中实现 IF() 的查询如下 −

mysql> select Value,IF(Value > 1000, CONCAT(Value,' is greater than 1000'),CONCAT(Value,' is lower than 1000')) AS Result from DemoTable;

这会产生以下输出−

+-------+---------------------------+
| Value | Result                    |
+-------+---------------------------+
| 1000  | 1000 is lower than 1000   |
| 2000  | 2000 is greater than 1000 |
| 500   | 500 is lower than 1000    |
| 1100  | 1100 is greater than 1000 |
+-------+---------------------------+
4 rows in set (0.00 sec)

Ankith Reddy

更新于： 2019-07-30

360 次浏览

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