Sub-queries in SQL

Question

Hi Friends Can we rewrite sub-queries into simple select statements or with joins ?

Nitesh Luharuka · Answer

Yes you can do this. Sub-queries are used to retrieve matched set of data based on certain conditions. The same can be done via Inner Joins. SubQuery ======== SELECT a.* FROM tb1 a WHERE a.col1 IN (SELECT b.col1 FROM tbl2 b) Joins ==== SELECT a.*b.* FROM tbl1 a JOIN tbl2 b ON a.col1=b.col1 With Joins you can retrieve any columns of the joining tables while with sub queries this is not possible.

Santhosh Kumar Jayaraman · Answer

yes.. You can write Select * from tbl1 where id in (select id from tbl2 where status='AC') You can rewrite it as select tbl1.* from tbl1 inner join tbl2 on tbl2.Id=tbl1.id where tbl2.status='AC'