Miscellaneous

1.          Hierarchical Queries
   A Hierarchical query built upon a parent-child relationship with in the same table or view
   SELECT  ename,sal,level
   FROM emp
   CONNECT BY PRIOR empno=mgr
   START WITH ename ='KING';
   
   2.       Oracle Hints : Effects the explain plan of a  query.
   Optimizer hints can be used with SQL statements to alter execution plans.
   Types:
   Single-table  Eg : INDEX and USE_NL
   Multi-table   Eg : LEADING
   Query-block Eg : STAR_TRANSFORMATION , UNNEST
   Statement Eg : ALL_ROWS
   
   3.       EXPLAIN PLAN
   The EXPLAIN PLAN statement displays execution plans chosen by the Oracle optimizer for SELECT, UPDATE, INSERT, and DELETE statements. A statement's execution plan is the sequence of operations Oracle performs to run the statement.