Answer Posted / neo devan

A query inside a query or next level query is called
subquery, a subquery can return 1 or more values to the
main query.
Ex: select * from emptable where deptno=(select deptno from
saltable where rownum=1);

A Join is used to query two tables, or views.
Ex: select * from emptable inner join saltable on
emptable.deptno=saltable.deptno;

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