declare @表1 table (id int,name int)
insert into @表1
select 1,2 union all
select 1,3 union all
select 1,4 union all
select 2,2 union all
select 2,3 union all
select 2,4 union all
select 3,1

select * from @表1

declare @表2 table (id int,age int)
insert into @表2
select 1,18 union all
select 3,18

select * from @表2

select a.* from @表1 a right join @表2 b on a.id=b.id

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SQL code

select 表1.* from 表1 inner join 表2 on 表1.id=表2.id and 表2.age=18

------解决方案--------------------
楼主要两个1,3,因此需要左连接left join

------解决方案--------------------
SQL code

SELECT * FROM 表1 where id in ( select id from 表2 where age ='18')

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结贴吧

------解决方案--------------------
select 表1.id as id,name
from 表1 left outer join  
(select id,age
from 表2
where age='条件') as 表3
on 表1.id = 表3.id