MySQL 查询给出不正确的结果

Question

我有一个表contribution_request

project_id | instrument_id
--------------------------
     1     |       5
     1     |       6

我需要检索具有 instrument_id=5 和 instrument_id=6 的 project_id 在此示例中将为 1。

我想这很简单，但我不知道该怎么做。

我尝试了很多不同的方法，但没有一个给我正确的结果。

喜欢:

SELECT cr.project_id 
FROM   contribution_request as cr 
WHERE  cr.project_id = 1 
  AND  cr.project_id = 6

或者这个

select p.id, cr.instrument_id from contribution_request as cr, project as p 
where p.id = cr.project_id 
  and cr.instrument_id = 1 
  and cr.instrument_id = 6  

请帮忙!

Answer 1

SQL Fiddle :

SELECT cr1.project_id 
FROM contribution_request as cr1
INNER JOIN contribution_request as cr2 ON cr1.project_id = cr2.project_id 
WHERE cr1.instrument_id = 5 AND cr2.instrument_id = 6