具有 NOT IN 和 WHERE 关系的 SQL 查询与 GUID

Question

有两个表Document和DocumentPos。在Document有列GUID和在DocumentPos是DocumentGUID指表的列Document。

我想让每一行都在DocumentPos它DocumentGUID现在的行中Documents' GUID。

我有这个返回 0 行的查询：

select *
FROM             Document d,
                 DocumentPos dp
WHERE            d.GUID = dp.DocumentGUID
AND              dp.DocumentGUID NOT IN (
                 SELECT d.GUID
                 FROM Document
)

但是当我执行select * from documentpos它时，例如返回一行DocumentGUID= B479BCB72334424DAC1B7CC26880DAB8。这DocumentGUID是NOT IN表Document作为GUID.

但select * from Document where GUID = 'B479BCB72334424DAC1B7CC26880DAB8'返回 0 行。

我想像这样构建查询，因为它应该成为一个DELETE语句：

DELETE           dp
FROM             Document d,
                 DocumentPos dp
WHERE            d.GUID = cp.DocmentGUID
AND              dp.DocumentGUID NOT IN (
                 SELECT d.GUID
                 FROM Document
)

第二个问题我也想知道：

为什么在括号中是FROM d不可能的，只有FROM Document？

Answer 1

NOT IN is tricky with NULLs. You can use NOT EXISTS instead, which is null-safe. Also, I cannot see why you need to bring in the document table in the outer query.

I think that you want:

select *
from documentpos dp
where not exists (
    select 1 from document d where d.guid = dp.documentguid
)

You can turn this to a delete statement as follows:

delete dp
from documentpos dp
where not exists (
    select 1 from document d where d.guid = dp.documentguid
)