sql - Sql 查询在多对多关系中查找不匹配的数据

Question

我需要有关 sql 查询的帮助。

我有两张桌子Person_Table 和PersonAlias_Table。在第一个表中， person_id和uniqe_id是主键，在别名表中， person_id和 uniqe_id 以及activity_code也是主键。我想找到在 Alias 表中但不在 person 表中的数据。

Answer 1

select *
  from PersonAlias_Table PA
       left outer join Person_Table P on PA.person_id = P.person_id 
       and PA.uniqe_id = P.uniqe_id
 where P.uniqe_id is null

试试这个

Answer 2

执行此操作的最佳方法取决于您的 DBMS，您可以使用NOT EXISTS或LEFT JOIN/IS NULL

不存在

SELECT  *
FROM    PersonAlias_Table pat
WHERE   NOT EXISTS
        (   SELECT  1
            FROM    Person_Table pt
            WHERE   pt.Person_ID = pat.Person_ID
            AND     pt.Uniqe_ID = pat.Uniqe_ID
        )

左连接/为空

SELECT  *
FROM    PersonAlias_Table pat
        LEFT JOIN Person_Table pt
            ON pt.Person_ID = pat.Person_ID
            AND pt.Uniqe_ID = pat.Uniqe_ID
WHERE    pt.Person_ID IS NULL

According to this answer in MySQL NOT EXISTS is a little bit less efficient, In SQL Server LEFT JOIN / IS NULL is less efficient, in PostgreSQL and Oracle both methods are the same, so it is really personal preference.