SQL 与 GUID 具有 NOT IN 和 WHERE 关系的查询

Question

有两个tableDocument和DocumentPos。在 Document 中有列 GUID，在 DocumentPos 中有列 DocumentGUID，它指的是 table Document.

I want to have every row in DocumentPos where its DocumentGUID has now row in Documents' GUID.

我有这个查询 returns 0 行：

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 时，它 returns 例如一行 DocumentGUID= B479BCB72334424DAC1B7CC26880DAB8。而这个DocumentGUID是NOT INtableDocument作为GUID。

但是 select * from Document where GUID = 'B479BCB72334424DAC1B7CC26880DAB8' returns 0 行。

我想像这样构建查询，因为它应该成为 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：

Why is in the brackets not FROM d possible and only FROM Document?

Answer 1

NOT IN 对于 NULL 是棘手的。您可以改用 NOT EXISTS，这是 null 安全的。另外，我不明白为什么你需要在外部查询中引入 document table。

我想你想要：

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

您可以将其转换为删除语句，如下所示：

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

Answer 2

我能理解的是您想从 DocumentPos table 中删除 Main table Document 中不存在的数据。您可以使用以下查询：

DELETE dp FROM DocumentPos dp
left join Document d on d.GUID = dp.DocumentGUID
where d.GUID is null

SQL 与 GUID 具有 NOT IN 和 WHERE 关系的查询

SQL query with NOT IN and WHERE relation with GUIDs

sql

sql-server

subquery

sql-delete

sql-null