when to denormalize, briefly

%%A: when select performance is kind of more important than DML performance
%%A: read-mostly DB

Q: any specific type of application you know
A: reporting, query, analysis, research, search

Q: How about data warehousing? Materialized views can be created from a join (?), therefore denormalized?
A: Not even close. Both can help performance. A Materilized view consists entirely of derived, redundant data. When the original data changes, this copy of redundant data is marked obsolete. If you add a bunch of triggers to always update the Materialized View to keep it in sync with original, then maybe it’s equivalent to a denormalized set of tables.

* joins — big joins are the problem
* summary tables like in GS are examples of denormalized tables.
* star schema on wikipedia

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