SQL查询：不使用子查询

Question

我怎样才能得到第一个表中的所有记录不存在于第二个表中而不使用子查询？ 我想用加入...

Answer 1

SELECT A.someColumn 
FROM A LEFT JOIN B 
ON A.ID = B.ID 
WHERE B.ID IS NULL 

Answer 2

你甚至可以使用

一）EXCEPT

B）Where Not in

例如 示例数据

declare @t1 table(id1 int, recordsA varchar(20)) 
insert into @t1 
select 1,'record1' union all 
select 2,'record2' union all 
select 3,'record3' union all 
select 4,'record4' union all 
select 5,'record5' 

declare @t2 table(id2 int, recordsB varchar(20)) 
insert into @t2 
select 1,'record1' union all 
select 2,'record2' union all 
select 3,'record3' 

查询：1

select t1.id1,t1.recordsA from @t1 t1 
except 
select t2.id2,t2.recordsB from @t2 t2 

问题2：

select t1.id1,t1.recordsA from @t1 t1 
where t1.recordsA not in(select t2.recordsB from @t2 t2) 

输出：

id1 recordsA 
4 record4 
5 record5