Relational Representation of Cross-tabs item-name color number Cross-tabs can be represented skirt dark 8 as relations skirt pastel 35 skirt white 10 We use the value all is used to skirt all 53 represent aggregates dress dark 20 The SQL:1999 standard dress pastel 10 actually uses null values in dress white 5 place of all despite confusion dress all 35 with regular null values shirt dark 14 shirt pastel 7 shirt white 28 shirt all 49 pant dark 20 pant pastel pant white 5 pant all 27 a dark 62 all pastel 54 a white 48 all 164 Database System Concepts-5th Edition,Aug 26,2005 18.7 @Silberschatz,Korth and Sudarshan
Database System Concepts - 5 18.7 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Relational Representation of Cross-tabs Cross-tabs can be represented as relations We use the value all is used to represent aggregates The SQL:1999 standard actually uses null values in place of all despite confusion with regular null values
Data Cube A data cube is a multidimensional generalization of a cross-tab Can have n dimensions;we show 3 below Cross-tabs can be used as views on a data cube 2 11 6 12 /29 2 /8 /5/7 /22 16 4 dark 8 20 14 20 62 34 18 pastel 35 10 7 2 54 9 21 0j05 45 white 10 8 28 5 48 42 small 77 medium all 53 35 49 27 164 large all size skirt dress shirts pant all item name Database System Concepts-5th Edition,Aug 26,2005 18.8 @Silberschatz,Korth and Sudarshan
Database System Concepts - 5 18.8 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Data Cube A data cube is a multidimensional generalization of a cross-tab Can have n dimensions; we show 3 below Cross-tabs can be used as views on a data cube
Online Analytical Processing Pivoting:changing the dimensions used in a cross-tab is called Slicing:creating a cross-tab for fixed values only Sometimes called dicing,particularly when values for multiple dimensions are fixed. Rollup:moving from finer-granularity data to a coarser granularity Drill down:The opposite operation-that of moving from coarser- granularity data to finer-granularity data Database System Concepts-5th Edition,Aug 26,2005 18.9 ©Silberschat乜，Korth and Sudarshan
Database System Concepts - 5 18.9 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Online Analytical Processing Pivoting: changing the dimensions used in a cross-tab is called Slicing: creating a cross-tab for fixed values only Sometimes called dicing, particularly when values for multiple dimensions are fixed. Rollup: moving from finer-granularity data to a coarser granularity Drill down: The opposite operation - that of moving from coarsergranularity data to finer-granularity data
Hierarchies on Dimensions Hierarchy on dimension attributes:lets dimensions to be viewed at different levels of detail E.g.the dimension DateTime can be used to aggregate by hour of day,date,day of week,month,quarter or year Year Quarter Region Day of week Month Country Hour of day Date State Date Time City a)Time Hierarchy b)Location Hierarchy Database System Concepts-5th Edition,Aug 26,2005 18.10 ©Silberschat乜，Korth and Sudarshan
Database System Concepts - 5 18.10 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Hierarchies on Dimensions Hierarchy on dimension attributes: lets dimensions to be viewed at different levels of detail E.g. the dimension DateTime can be used to aggregate by hour of day, date, day of week, month, quarter or year
Cross Tabulation With Hierarchy Cross-tabs can be easily extended to deal with hierarchies Can drill down or roll up on a hierarchy category item-name dark pastel white total womenswear skirt 8 8 10 53 dress 20 20 5 35 subtotal 28 28 15 88 menswear pants 14 14 28 49 shirt 20 20 5 27 subtotal 34 34 33 76 total 62 62 48 164 Database System Concepts-5th Edition,Aug 26,2005 18.11 @Silberschatz,Korth and Sudarshan
Database System Concepts - 5 18.11 ©Silberschatz, Korth and Sudarshan th Edition, Aug 26, 2005 Cross Tabulation With Hierarchy Cross-tabs can be easily extended to deal with hierarchies Can drill down or roll up on a hierarchy