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MySQL Merge一起选择吗？

2024-05-01 03:52:04 455

要将选择合并在一起，您需要使用GROUPBY子句。为了理解这个概念，让我们创建一个表。创建表的查询如下-

mysql> create table MergingSelectDemo
   -> (
   -> RoomServicesId int,
   -> RoomId int,
   -> ServiceId int
   -> );

现在，您可以使用insert命令在表中插入一些记录。查询如下-

mysql> insert into MergingSelectDemo values(10,10,10);
mysql> insert into MergingSelectDemo values(20,10,20);
mysql> insert into MergingSelectDemo values(30,10,30);
mysql> insert into MergingSelectDemo values(50,10,50);
mysql> insert into MergingSelectDemo values(110,20,20);
mysql> insert into MergingSelectDemo values(120,20,30);

使用select语句显示表中的所有记录。查询如下-

mysql> select *from MergingSelectDemo;

以下是输出-

+----------------+--------+-----------+
| RoomServicesId | RoomId | ServiceId |
+----------------+--------+-----------+
|             10 |     10 |        10 |
|             20 |     10 |        20 |
|             30 |     10 |        30 |
|             50 |     10 |        50 |
|            110 |     20 |        20 |
|            120 |     20 |        30 |
+----------------+--------+-----------+
6 rows in set (0.00 sec)

这是将选择合并在一起的查询-

mysql> select RoomId from MergingSelectDemo
   -> where ServiceId IN(10,20,30)
   -> group by RoomId
   -> HAVING COUNT(*)=3;

以下是输出-

+--------+
| RoomId |
+--------+
|     10 |
+--------+
1 row in set (0.15 sec)

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MySQL Merge一起选择吗？

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