sql - SQL 导航器中的 "with... as"

Question

以下查询有效:

select count(*) from everything where num not in (select num from sometable)

以下查询应该等同于上述查询，但会导致“无效标识符”错误:

with unwanted as (select num from sometable)
select count(*) from everything where num not in unwanted

第二个查询有什么问题？

Answer 1

语法是这样的:

with unwanted as (select num from sometable)
select count(*) from everything where num not in (select * from unwanted)

显然这只有在 select num from sometable 时才有意义部分有点复杂或稍后使用几次......