NTILE:-
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THIS FUNCTION FINDS EACH ROWS PLACE IN THE RANKING ,AND THEN ASSIGNS EACH ROW TO A BUCKET SUCH THAT EVERY BUCKET CONTAINS THE SAME NO OF ROWS.IF THE NUMBER OF ROWS IS NOT EVENLY DIVISIBLE BY THE NUMBER OF BUCKETS,THEN THE EXTRA ROWS ARE DISTRIBUTED SO THAT THE NUMBER OF ROWS PER BUCKET DIFFERS BY ONE AT MOST.THIS APPROACH IS REFERRED TO AS "EQUIHEIGHT BUCKETS" BECAUSE EACH BUCKET CONTAINS 'ALMOST' THE SAME NUMBER OF ROWS.
Sample Example
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SELECT DEPTNO,EMPNO,SUM(SAL) SALARY,NTILE(4) OVER (ORDER BY SUM(SAL)DESC) QUARTER FROM EMP
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GROUP BY DEPTNO,EMPNO
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ORDER BY QUARTER,SALARY DESC;
