The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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sql – How to Select Every Row Where Column Value is NOT Distinct – Stack Overflow

Posted by jpluimers on 2019/05/22

Since I always forget that IN and EXISTS have very different performance characteristics: [WayBack] sql – How to Select Every Row Where Column Value is NOT Distinct – Stack Overflow

Less slow

select emailaddress,customername from customers where emailaddress in
(select emailaddress from customers group by emailaddress having count(*) > 1)

Slow

select emailaddress,customername from Customers a where exists
(select emailaddress from customers c where a.customerName != c.customerName and a.EmailAddress = c.EmailAddress)

–jeroen

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