如何从2个表1到多个表中计算“多侧”实体

Question

在MySQL中，我有两个与“一对多”关系相关的表。如何从表1(“单侧”)中选择in，它在表2(“多端”)中准确地具有与N相关的值。我试着用：

 SELECT target_id, COUNT(`target_id`) AS counter FROM `many_side_table` WHERE counter = N GROUP BY target_id; 

 SELECT target_id, COUNT(`target_id`) FROM `many_side_table` WHERE COUNT(`target_id`) = N GROUP BY target_id; 

但这是错误的..。

Answer 1

我想你只想要having条款：

SELECT target_id, COUNT(`target_id`)
FROM `many_side_table`
GROUP BY target_id
HAVING COUNT(`target_id`) = N;

Answer 2

SELECT target_id 
FROM many_side_table
GROUP BY target_id
HAVING COUNT(*) = N