Jaa

Database Programming: Did You Know IN Can Do This?

  • Artikkeli

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!

-wp

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