Extended Aggregation in SQL:1999 The cube operation computes union of group by's on every subset of the specified attributes E.g.consider the query select item-name,color,size,sum(number) from sales group by cube(item-name,color,size) This computes the union of eight different groupings of the sales relation: {(item-name,color,size),(item-name,color), (item-name,size), (color,size), (item-name), (color, (size), ()} where ()denotes an empty group by list. For each grouping,the result contains the null value for attributes not present in the grouping. Database System Concepts-5th Edition,Aug 26,2005 18.14 @Silberschatz,Korth and SudarshanDatabase System Concepts - 5 18.14 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Extended Aggregation in SQL:1999 The cube operation computes union of group by’s on every subset of the specified attributes E.g. consider the query select item-name, color, size, sum(number) from sales group by cube(item-name, color, size) This computes the union of eight different groupings of the sales relation: { (item-name, color, size), (item-name, color), (item-name, size), (color, size), (item-name), (color), (size), ( ) } where ( ) denotes an empty group by list. For each grouping, the result contains the null value for attributes not present in the grouping