如何在MySQL查询中正确插入IF语句？

要在MySQL查询中插入IF语句，请使用以下语法：

select yourColumnName ,if(yourCondition, yourStatement1,yourStatement2) from yourTableName;

首先让我们创建一个表 –

mysql> create table DemoTable1571
   -> (
   -> Id int,
   -> Value int
   -> );
Query OK, 0 rows affected (5.63 sec)

使用插入命令在表中插入一些记录 –

mysql> insert into DemoTable1571 values(101,500);
Query OK, 1 row affected (1.07 sec)
mysql> insert into DemoTable1571 values(102,450);
Query OK, 1 row affected (0.47 sec)
mysql> insert into DemoTable1571 values(103,300);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable1571 values(104,700);
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 DemoTable1571;

这将产生以下输出

+------+-------+
| Id   | Value |
+------+-------+
|  101 |   500 |
|  102 |   450 |
|  103 |   300 |
|  104 |   700 |
+------+-------+
4 rows in set (0.00 sec)

以下是将IF语句正确插入MySQL查询的查询。

mysql> select Value,if(Value > 550, 'Value is greater than 550','Value is less than 550') from DemoTable1571;

这将产生以下输出 –

+-------+-----------------------------------------------------------------------+
| Value | if(Value > 550, 'Value is greater than 550','Value is less than 550') |
+-------+-----------------------------------------------------------------------+
|   500 | Value is less than 550                                                |
|   450 | Value is less than 550                                                |
|   300 | Value is less than 550                                                |
|   700 | Value is greater than 550                                             |
+-------+-----------------------------------------------------------------------+
4 rows in set (0.00 sec)

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