how to optimize sql query for 9000 code example

Example: optimize sql query

-- ORACLE: get explain plan for a query
-- Without execution
EXPLAIN PLAN FOR select ...;
SELECT * FROM TABLE(dbms_xplan.display);
-- With execution
SELECT /*+ gather_plan_statistics */  ...;
SELECT * FROM TABLE(dbms_xplan.display_cursor(NULL,NULL,'ALLSTATS LAST'));