MySQL：使用上一个查询的结果创建具有多个SELECTS的查询

Question

我想检索具有特定值的行数，但是此值取决于在使用此结果之前必须执行的查询

已知变量为adId，例如adId为32 所以我想获得requestFrom的值，其中adId = 32

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

然后我得到了计数：

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

- 我只想在一个查询中执行此操作（获取计数）

+----+--------+-------------+------+--------+
| 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

使用子查询获取此信息

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