如何在MySQL的SELECT语句中使用if/else条件？

首先让我们创建一张表 –

mysql> create table DemoTable1966
   (
   UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   UserName varchar(20),
   PhotoLiked int
   );
Query OK, 0 rows affected (0.00 sec)

使用insert命令向表中插入一些记录 –

mysql> insert into DemoTable1966(UserName,PhotoLiked) values('Chris',57);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1966(UserName,PhotoLiked) values('David',100);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1966(UserName,PhotoLiked) values('Mike',68);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1966(UserName,PhotoLiked) values('Sam',78);
Query OK, 1 row affected (0.00 sec)

使用select语句从表中显示所有记录 –

mysql> select * from DemoTable1966;

它将产生以下输出 –

+--------+----------+------------+
| UserId | UserName | PhotoLiked |
+--------+----------+------------+
|      1 | Chris    |         57 |
|      2 | David    |        100 |
|      3 | Mike     |         68 |
|      4 | Sam      |         78 |
+--------+----------+------------+
4 rows in set (0.00 sec)

这是在MySQL中使用SELECT语句中if / else条件的查询 –

mysql> select if(PhotoLiked > 75,UserName,'Likes are less') as Result from DemoTable1966;

它将产生以下输出 –

+------------------------------------------------+
| Result                                         |
+------------------------------------------------+
| Likes are less                                 |
| David                                          |
| Likes are less                                 |
| Sam                                            |
+------------------------------------------------+
4 rows in set (0.00 sec)

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