MySQL：使用上一个查询的结果创建一个包含多个SELECTS的查询

Question

I want to retrieve the count of rows with a specific value, But this value depends on a query that must be done before using this result

The known variable is adId, for example adId is 32 So I want to get the value of the requestFrom where adId = 32

Easy: $result = SELECT requestFrom FROM myTable WHERE adId = 32

Then I get the count:

SELECT COUNT(*) FROM myTable WHERE requestFrom = $result AND adId = $adId AND requestStatus = '1'

- I want to do this (get the count) in only one query

+----+--------+-------------+------+--------+
| id | userId | requestFrom | adId | status |
+----+--------+-------------+------+--------+
|  1 |     23 |          58 |   32 |      1 |
|  2 |     23 |          65 |   37 |      0 |
|  3 |     76 |          27 |   73 |      1 |
|  4 |     29 |          58 |   29 |      1 |

Answer 1

Use Sub query to get this

SELECT COUNT(*) FROM myTable 
WHERE requestFrom = (select requestFrom from myTable where adId = $adId ) 
AND adId = $adId AND requestStatus = '1'