mysql - 按日期计算来自多个表和组的总数据

Question

我有3张 table

1. 设备1

+-------------+-------------+-------------+  
| id_skt1     | status_kt1  | tgl_skt1    |
+-------------+-------------+-------------+
|      1      | ON          | 2019-07-23  |
+-------------+-------------+-------------+
|      2      | ON          | 2019-07-23  |
+-------------+-------------+-------------+
|      3      | ON          | 2019-07-24  |
+-------------+-------------+-------------+

2. equipment2

+-------------+-------------+-------------+
| id_skt2     | status_kt2  | tgl_skt2    |
+-------------+-------------+-------------+
|      1      | ON          | 2019-07-23  |
+-------------+-------------+-------------+
|      2      | OFF         | 2019-07-23  |
+-------------+-------------+-------------+
|      3      | ON          | 2019-07-25  |
+-------------+-------------+-------------+

3. equipment3

 
+-------------+-------------+-------------+
| id_skt3     | status_kt3  | tgl_skt3    |
+-------------+-------------+-------------+
|      1      | OFF         | 2019-07-25  |
+-------------+-------------+-------------+
|      2      | ON          | 2019-07-26  |
+-------------+-------------+-------------+
|      3      | ON          | 2019-07-26  |
+-------------+-------------+-------------+
|      4      | ON          | 2019-07-27  |
+-------------+-------------+-------------+
|      5      | ON          | 2019-07-27  |
+-------------+-------------+-------------+
|      6      | ON          | 2019-07-27  |
+-------------+-------------+-------------+

how to count all status "ON" on these tables and group by date?

I have searched the website SO but i haven't found a similar problem

i've tried using this code:

SELECT (SELECT  COUNT(*) FROM status_kt1 WHERE status_kt1="ON") as T1, (SELECT  COUNT(*) FROM status_kt2 WHERE status_kt2="ON") as T2, (SELECT  COUNT(*) FROM status_kt3 WHERE status_kt3="ON") as T3

I have searched the website so but did not find a similar problem


I want the results like this:

+-------------+-------------+  
| tgl_all     |totalStatusOn|
+-------------+-------------+
| 2019-07-23  |    3        |
+-------------+-------------+
| 2019-07-24  |    1        |
+-------------+-------------+
| 2019-07-25  |    1        |
+-------------+-------------+
| 2019-07-26  |    2        |
+-------------+-------------+
| 2019-07-27  |    3        |
+-------------+-------------+

问候 :)

Answer 1

连接所有表格并从结果中选择:

select tgl_all, count(tgl_all) as totalStatusOn from (
  select status_kt1 as status, tgl_skt1 as tgl_all from equipment1
  union all select status_kt2 as status, tgl_skt2 as tgl_all from equipment2
  union all select status_kt3 as status, tgl_skt3 as tgl_all from equipment3) t
  where status='ON' group by tgl_all;

tgl_all     totalStatusOn
2019-07-23  3
2019-07-24  1
2019-07-25  1
2019-07-26  2
2019-07-27  3

顺便说一句，这似乎是一个糟糕的设计，如果你只有一张表，其中包含用于设备类型的附加字段，那会更好。