Answer Posted / asnani_satish@yahoo.com

Minor correction in above answer
Difference between sub-query, correlated query and query as
table
1. Sub-query : the inner query is executed in entirety
before the outer query is executed
eg select * from emp where deptno in (select deptno from dept);

2. Correlated Query: For each record fetched in outer query
corresponding matching records are fetched in sub-query
because of join condition within inner sub-query. Answers
1,2,3 are correct

3. Query as Table: A query can behave as a table

select a.empno,a.sal,a.sal/b.avgsal*100 as percent_avg_sal
from emp a,(select deptno,avg(sal) avgsal from emp group by
deptno) b
where a.deptno=b.deptno;

Here the entire "(select deptno,avg(sal).....)" behaves as
table named "b" containing dept wise average sal. The query
is behaving as a temporary table.

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