如何在 MySQL 中的 select 中使用 if/else 条件?
mysqlmysqli database更新于 2024/12/7 6:36:17
首先我们创建一个表 −
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 命令在表中插入一些记录 −
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 语句显示表中的所有记录 −
mysql> select * from DemoTable1966;
这将产生以下输出 −
+--------+----------+------------+ | 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 的 SELECT 中使用 if/else 条件的查询 −
mysql> select if(PhotoLiked > 75,UserName,'Likes are less') as Result from DemoTable1966;
这将产生以下输出 −
+------------------------------------------------+ | Result | +------------------------------------------------+ | Likes are less | | David | | Likes are less | | Sam | +------------------------------------------------+ 4 rows in set (0.00 sec)
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mysql 参考教程 - 该教程包含有关 mysql 的更多信息:https://www.cainiaomax.com/mysql/
