mysql查询 - 记录另一条记录

Question

表：成员

fields:
member_id - unique primary id
voter_id - the member_id of another record

John Doe - member_id = 1, voter_id = 0
ABC Inc. - member_id = 2, voter_id = 1 (John Doe is the voter)

我需要提取所有记录，其中member_id永远不会出现在voter_id字段中。在这种情况下，我需要它来查找member_id 2，但不是member_id 1。

谢谢你们。我看了，但没有在这里找到答案。

Answer 1

有很多方法可以做到这一点......这里有一些。 子选择

SELECT * 
FROM  member 
WHERE member_ID not in (select voter_ID from member)

JOIN

SELECT  * 
FROM member ma
LEFT join member mb on mb.voter_Id = ma.member_Id and Mb.meber_ID is null

EXISTS

SELECT Member_ID, Voter_ID 
FROM member MA 
WHERE not exists (Select 1 from member MA where MA.Member_ID = MB.Voter_ID)

选择哪个取决于很多东西，但这里只有一个opinion

Answer 2

尝试缺少匹配自我加入：

SELECT m1.member_id
FROM member m1
LEFT JOIN member m2 ON m2.voter_id = m1.member_id
AND m2.member_id IS NULL

Answer 3

SELECT * from member WHERE member_id NOT IN (SELECT voter_id FROM member);