如何查找违反参照完整性的记录

Question

我有两个表应该是一对多的关系，但是在表的许多方面似乎存在一些阻止创建关系的记录。违反参照完整性。

由于两个表中都有很多记录，有没有办法查询哪些记录在多方面，而不是在一方？

**Ex.**

Table 1: (one side)
(pk)AccountId


Table 2: (many side)
(pk)UserId
(fk)AccountId  <--  Some accountId's are not in Table 1 

Answer 1

select *
from table2 t2
where not exists(
    select 1
    from table1 t1
    where t1.AccountId = t2.AccountId
)

Answer 2

select a.*
from Table2 as a
where not exists (select null from table1 as b where b.AccountId = a.AccountId);

Answer 3

SELECT table2.UserId, table2.AccountId
FROM table1 RIGHT JOIN table2 ON table1.AccountId = table2.AccountId
WHERE table1.AccountId IS NULL;

http://sqlfiddle.com/#!3/5b8e30/4

Answer 4

FROM Table2 t2
WHERE t2.AccountId not in (SELECT t1.AccountId FROM Table1 t1)

或者如果您更喜欢加入......

FROM Table2 t2
  LEFT JOIN Table1 t1
  ON t2.AccountId = t1.AccountId
WHERE t1.AccountId is null