Courtesy of Jens Suessmeyer comes this little gem purloined from an internal discussion; cut-and-paste this into SQL Server Management Studio and see if you can answer the questions in the comments before you execute the script:
-- create and populate a table variable DECLARE @Demonstration TABLE ( ID INT IDENTITY(1,1), Col1 INT, Col2 INT, Col3 INT ) INSERT @Demonstration (Col1,Col2,Col3) VALUES (1, 2, 100) INSERT @Demonstration (Col1,Col2,Col3) VALUES (2, 100, 1) INSERT @Demonstration (Col1,Col2,Col3) VALUES (100, 1, 2) -- this one you can probably guess.. SELECT ID FROM @Demonstration WHERE Col1 IN (1,2) -- but what's going to happen here? SELECT ID FROM @Demonstration WHERE 1 IN (Col1,Col2)
I knew IN could examine a column for a list of values; I didn’t know that it could examine a list of columns for a value. For the record, here’s the result set:
ID 1 2
ID 1 3
This works in every version of SQL Server as far back as I can check (SQL Server 2000 SP4). Thanks, Jens, for debunking a case of one-dimensional thinking on my part!
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