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Sunday, January 20, 2008

SQL queries case sensitive

If you installed SQL Server with the default collation options, you might find that the following queries return the same results:

CREATE TABLE mytable
(
mycolumn VARCHAR(10)
)
GO

SET NOCOUNT ON

INSERT mytable VALUES('Case')
GO

SELECT mycolumn FROM mytable WHERE mycolumn='Case'
SELECT mycolumn FROM mytable WHERE mycolumn='caSE'
SELECT mycolumn FROM mytable WHERE mycolumn='case'

You can alter your query by forcing collation at the column level:

SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = 'caSE'

SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = 'case'

SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = 'Case'

-- if myColumn has an index, you will likely benefit by adding
-- AND myColumn = 'case'

If you want to do this in a more global way, instead of modifying each individual query, you can force the collation at the database level, or at the column level, using the ALTER DATABASE and ALTER TABLE commands, respectively.

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