MySQL 如何在单个MySQL查询中合并查询以获取不同列中不同值的计数

首先让我们创建一个表−

mysql> create table DemoTable760 (
   ClientId int,
   ClientId2 int
);
Query OK, 0 rows affected (0.79 sec)

使用insert命令在表中插入一些记录−

mysql> insert into DemoTable760 values(100,200);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable760 values(100,200);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable760 values(300,400);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable760 values(300,400);
Query OK, 1 row affected (0.26 sec)
mysql> insert into DemoTable760 values(100,200);
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable760 values(100,200);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable760 values(400,500);
Query OK, 1 row affected (0.08 sec)

使用select语句显示表中的所有记录−

mysql> select *from DemoTable760;

这将产生以下输出 –

+----------+-----------+
| ClientId | ClientId2 |
+----------+-----------+
|      100 |       200 |
|      100 |       200 |
|      300 |       400 |
|      300 |       400 |
|      100 |       200 |
|      100 |       200 |
|      400 |       500 |
+----------+-----------+
7 rows in set (0.00 sec)

以下是在单个查询中合并查询以获取不同列中不同值计数的查询−

mysql> select sum(ClientId=100) AS ClientId1,sum(ClientId2=200) AS ClientId2 from DemoTable760;

这将产生以下输出 −

+-----------+-----------+
| ClientId1 | ClientId2 |
+-----------+-----------+
|         4 |         4 |
+-----------+-----------+
1 row in set (0.00 sec)

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