Writing Analytics SQL with Common Table Expressions(research.neustar.biz)
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Writing Analytics SQL with Common Table Expressions
http://research.neustar.biz/2014/05/19/writing-analytics-sql-with-common-table-expressions/
3 comments
Some RDBMSs support recursive CTEs, which come in handy sometimes. SQLite added support earlier this year, and I've written a handful of recursive CTEs to traverse DAGs in the database. I was blown away by how quickly SQLite can handle queries like that!
Recursive CTEs are part of the SQL:1999 standard and actually make SQL into Turing complete language. I didn't realise SQLite had implemented CTEs, let alone recursive ones...I'll have to play :)
DbFit (http://dbfit.github.io/dbfit/) provides a more heavy-weight, but much more scalable alternative to raw SQL for testing CTEs.
In SQL Server, CTEs eventually slow down then temp tables win because they can have indexes.