BUSI 3400 Lecture Notes - Lecture 11: Apache Hadoop, Fact Table, Data Cube
Document Summary
Index a secondary file structure that provides an alternative path to the data. Data sparsity number of different values a column could have. B+ tree provides improved performance on sequential and range searches. All keys are redundantly stored in the leaf nodes. Bitmap strings of bits, one for each row. Measure of the likelihood that an index will be used in query processing. Short-term decisions: fulfill orders, resolve complaints, provide staffing. Medium and long-term decisions: capacity planning, store locations, product promotion, new lines of business. Decision support data time span, granularity (drill down, roll up), Data warehouse definition characteristics data from operational databases and external data sources. Dimension keys (link fact table to the dimensions), Facts (measure details), grain is the level of detail that the facts are stored. Primary purpose is to facilitate analysis by allowing managers to slice/dice. Represent the characteristics of what is being measured (ie. what is in the fact table)