主从表查询,该如何处理

主从表查询
主表字段

SQL code

id inttitle varchar

SQL code

id intparentid int  --主表的IDfilename varchar

SQL code

select top 25 a.* from ta a join tb b on a.id=b.parentid where b.filename is not null or filename<>''
[解决办法]
SQL code
select top 25 a.* from tb a,tb b where a.id=b.id and b.filename is not null
[解决办法]
SQL code
SELECT  TOP 25 a.* FROM  ta a,tb b WHERE a.id=b.parentid AND( b.filename is not null AND b.filename<>'')
[解决办法]
SQL code
select top 25 p.id,p.title,s.filename from temp_main as p inner join temp_detail as son p.id=s.parentid where filename is not null or filename<>''