Data Cube and OLAP Server Madhavi Gundavarapu

Data Cube and OLAP Server Outline What is Data Analysis? Steps in Data Analysis SQL-92 Aggregate Functions Limitations of GROUP BY OLAP Server CUBE Operator ROLLUP Operator Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server What is Data Analysis? DATA ANALYSIS query exact response User issues a query, receives a response and formulates the next query based on the response This process repeats until the user gets the required result Fundamentally an iterative process Hello mahesh Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Why Data Analysis? Search for unusual patterns of data Summarize data values Extract statistical information Contrast one category with another Provide a consolidated view of enterprise data buried in OLTP databases Help Decision makers understand business trends Derive intelligible results from ad hoc, voluminous and scattered data Hello mahesh Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Steps in Data Analysis Formulate query Extract aggregated data Visualize results Analyze Analyze & Formulate Extract Visualize Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Overview of SQL-92 SQL has several aggregate operators: sum(), count(), avg(), min(), max() The basic idea is: Combine all values in a column into a single scalar value Syntax SELECT sum(units) FROM inventory; Madhavi Gundavarapu Data Cube and OLAP Server

Overview of SQL-92 (contd.): Distinct Clause Allows aggregation over distinct values Example SELCT COUNT(DISTINCT locations) FROM inventory; Madhavi Gundavarapu Data Cube and OLAP Server

Overview of SQL-92 (contd.): GROUP BY Clause Group By allows aggregates over table sub-groups Result is a new table Syntax: SELCT location, sum(units) FROM inventory GROUP BY location HAVING nation = “USA”; Madhavi Gundavarapu Data Cube and OLAP Server

Limitations of GROUP BY Users want CrossTabs GROUP BY is limited to 0-D and 1-D aggregates Users want sub-totals and totals drill-down & roll-up reports M T W T F S S  AIR HOTEL FOOD MISC sum Madhavi Gundavarapu Data Cube and OLAP Server

Multidimensional Data Measure Attributes Dimension Attributes Example Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server OLAP System On-Line Analytical Processing System Interactive system Permits analysts to view summaries of multidimensional data On-Line indicates No long waits to see result of a query response times within a few seconds for new summaries View data at different levels of granularity Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server SQL:1999 OLAP Extensions SQL-92 functionality was limited SQL:1999 standard defines CUBE ROLLUP as generalizations of GROUP BY clause Madhavi Gundavarapu Data Cube and OLAP Server

CUBE : Relational Aggregate Operator N-dimensional generalization of simple aggregate functions CHEVY FORD 1990 1991 1992 1993 RED WHITE BLUE By Color By Make & Color By Make & Year By Color & Year By Make By Year Sum The Data Cube and The Sub-Space Aggregates Chevy Ford Cross Tab Group By (with total) Aggregate The CUBE operator is the N-dimensional generalization of simple aggregate functions. The 0D data cube is a point. The 1D data cube is a line with a point. The 2D data cube is a cross tabulation, a plane, two lines, and a point. The 3D data cube is a cube with three intersecting 2D cross tabs. Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server CUBE : The Idea 0-dimensional Aggregate (sum(), max(),...) a1, a2, ...., aN, f() Super-aggregate over 1-Dimensional sub-cubes ALL, a2, ...., aN , f() a1, ALL, a3, ...., aN , f() ... a1, a2, ...., ALL, f() Super-aggregate over 2-Dimensional sub-cubes ALL, ALL, a3, ...., aN , f() a1, a2 ,...., ALL, ALL, f() Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server An Example SELECT model, year, color, sum(sales) as sales FROM sales WHERE model in (‘Chevy’) AND year BETWEEN 1990 AND 1992 GROUP BY CUBE (model, year, color); Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server CUBE Contd. SELECT model, year, color, sum(sales) as sales FROM sales WHERE model in (‘Chevy’) AND year BETWEEN 1990 AND 1992 GROUP BY CUBE (model, year, color); Computes union of 8 different groupings: {(model, year, color), (model, year), (model, color), (year, color), (model), (year), (color), ()} Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Example Contd. CUBE Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server GROUPING Function SQL:1999 uses NULL to represent both ALL and regular null values GROUPING function Can be applied to an attribute Returns 1 if NULL value represents ALL Returns 0 in all other cases Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server GROUPING Example SELECT model, year, color, sum(sales) as sales, GROUPING(model) as model_flag, GROUPING(year) as year_flag, GROUPING(color) as color_flag FROM sales WHERE model in (‘Chevy’) AND year BETWEEN 1990 AND 1992 GROUP BY CUBE (model, year, color); Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Rollup and Drill down Allow analysts to view data at any desired level of granularity Rollup Operation of moving from finer-granularity of data to a coarser granularity Drill Down Operation of moving from coarser-granularity of data to a finer granularity Cannot be generated from coarse-granularity data Has to be computed from original data Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server ROLLUP Operator Rollup example SELECT model, year, color, sum(sales) as sales FROM sales WHERE model in (‘Chevy’) AND year BETWEEN 1990 AND 1992 GROUP BY ROLLUP (model, year, color); Only 4 groupings are generated {(model, year, color), (model, year), (model), ()} Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Summary SQL-92 has limited functionality to support OLAP operations SQL:1999 has introduced extensions to address these limitations provides operators such as CUBE, GROUPING and ROLLUP Madhavi Gundavarapu Data Cube and OLAP Server

Data Cube and OLAP Server Questions Madhavi Gundavarapu Data Cube and OLAP Server