SQL 服务器全部（select ...）为空

Question

我搜索过，但找不到任何相关信息。我需要 SQL 服务器查询，例如

select t1.x 
 from @tablename as t1 
 where all
   (select t2.y from @tablename as t2 where t1.x=t2.x) is null

@tablename相同

但我无法使用 all(select ...) is null 部分查询。

谢谢。

Answer 1

你要not exists吗？

select t1.x 
from @tablename as t1 
where not exists (select t2.y from @tablename as t2 where t1.x = t2.x)

这测试没有匹配值。

或者，也许，

select t1.x 
from @tablename t1 
where not exists (select 1
                  from @tablename as t2
                  where t1.x = t2.x and t2.y is not null
                 ) ;

这测试任何匹配值都具有 NULL for y。

SQL 服务器全部（select ...）为空

SQL Server all(select ...) is null

mysql

sql

sql-server

isnull