4- a)Assume that X,Y, Z are dimensions in an OLAP application. Indicate what is produced by the following statement? SELECT X,Y, Z , SUM (Amount) AS Sale (Other statements ) GROUP BY ROLLUP (Z, Y, X ); b) What was the reason for GROUP BY ROLLUP( ) and GROUP BY CUBE( ) extensios to SQL standard ? 5.Using your own tables in question1 : a) Give a sample query for a slice operation. b)Give a sample query for a dice operation 6. a) Define a simple table and write a query to compute moving average orders including : previous ,current, next days. b) Write 5 sample rows of your table and show the output from your query. c)What is the meaning of NTILE (20) ?