Connect By and Prior clause

[Anon]

What is level and connect by prior stand for in Oracle and what are it's uses ?

[Anon]

The following CONNECT BY clause defines a hierarchical relationship in which the EMPNO value of the parent row is equal to the MGR value of the child row:

CONNECT BY PRIOR empno = mgr;

In the following CONNECT BY clause, the PRIOR operator applies only to the EMPNO value. To evaluate this condition, Oracle evaluates EMPNO values for the parent row and MGR, SAL, and COMM values for the child row:

CONNECT BY PRIOR empno = mgr AND sal > comm;

[Anon]

Connect by and prior are used to permit queries on hierarchical data - data where children rows have a single parent row. It allows you to write a relatively simple query that will traverse the tree and give you the contents in various ways.