使用 MySQL GROUP BY 和 HAVING 显示具有非重复 Id 的记录

我们首先创建一个表 −

mysql> create table DemoTable
(
   Id int,
   ColorName varchar(100)
);
Query OK, 0 rows affected (0.56 sec)

使用插入命令在表中插入一些记录 −

mysql> insert into DemoTable values(100,'Red');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable values(101,'Green');
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values(101,'Blue');
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable values(102,'Yellow');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values(100,'Purple');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values(100,'Black');
Query OK, 1 row affected (0.26 sec)

使用选择语句从表中显示所有记录 −

mysql> select *from DemoTable;

这将产生以下输出 −

+------+-----------+
| Id   | ColorName |
+------+-----------+
|  100 | Red       |
|  101 | Green     |
|  101 | Blue      |
|  102 | Yellow    |
|  100 | Purple    |
|  100 | Black     |
+------+-----------+
6 rows in set (0.00 sec)

以下是显示具有非重复 Id 的记录的查询 −

mysql> select *from DemoTable
where Id in(select Id from DemoTable group by Id having count(*) < 2);

这将产生以下输出 −

+------+-----------+
|   Id | ColorName |
+------+-----------+
|  102 | Yellow    |
+------+-----------+
1 row in set (0.07 sec)

更新于:2019-09-30

123 次浏览

开启您的 职业

通过完成课程获得认证

开始
广告