Left outer Joins Vs Not Exists

Aaron Bertrand @ SQL Performance with a great comparison of methods of getting data where other data doesn’t exist

I’m in the habit of using left outer joins, but, as this post explains, you have to be careful when looking at nullable columns

the kicker is the performance gains to be had with NOT EXISTS & EXCEPT

http://www.sqlperformance.com/2012/12/t-sql-queries/left-anti-semi-join

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