OLAP notes
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OLAP notes
Some random OLAP notes by Dang 09:00, 27 June 2007 (PDT)
Star schema
- central table with columns for identifiers (foreign keys) and "facts" (values)
- one satellite table per foreign key w/additional attributes
- if satellite tables are in 3NF, then it's called a 'snowflake' schema, but this is a p.i.t.a. to query
Aggregation
Built-in functions: sum, count, min, max
Can define hierarchies based on subranges of values, e.g. timestamp can be broken down into Year, Month, Day, Hour, etc. This makes browsing much easier for large sets of distinct values.
Tools
Stack:
- Business Intelligence Development Studio (BIDS)
- XMLA (XML for Analysis)
- Microsoft Analysis Services
- MDX
- OLAP
- MS SQL Server (RDBMS)
