To make SQL Queries Case Sensitive

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Introduction

How to make SQL queries case sensitive.

How to do it?

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 = 'case' AND 
CAST(mycolumn AS VARBINARY(10)) = CAST('Case' AS VARBINARY(10)) 
SELECT mycolumn FROM mytable WHERE 
mycolumn = 'case' AND 
CAST(mycolumn AS VARBINARY(10)) = CAST('caSE' AS VARBINARY(10)) 
SELECT mycolumn FROM mytable WHERE 
mycolumn = 'case' AND 
CAST(mycolumn AS VARBINARY(10)) = CAST('case' AS VARBINARY(10)) 
-- 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. You can see the current collation level on the properties tab of the database server, through Enterprise Manager (if you're going to change this setting, MAKE NOTE OF THIS VALUE):

And you can see the description from running the following query: 

SELECT DATABASEPROPERTYEX('<databasename>', 'Collation')

As changing this setting can impact applications and SQL queries, I would isolate this test first. In SQL Server 2000, you can easily run an ALTER TABLE statement to change the sort order of a specific column, forcing it to be case sensitive. First, execute the following query to determine what you need to change it back to:

EXEC sp_help
'mytable'

The second recordset should contain the following information, in a default scenario:

Column_Name Collation 

----------- ---------------------------------------------- 

mycolumn    SQL_Latin1_General_CP1_CI_AS

Whatever the 'Collation' column returns, you now know what you need to change it back to after you make the following change, which will force case sensitivity:

 
ALTER TABLE mytable 
ALTER COLUMN mycolumn
VARCHAR(10) 
COLLATE
Latin1_General_CS_AS 
GO 
SELECT mycolumn FROM mytable WHERE
mycolumn='Case' 
SELECT mycolumn FROM mytable WHERE
mycolumn='caSE' 
SELECT mycolumn FROM
mytable WHERE mycolumn='case'

If this screws things up, you can change it back, simply by issuing a new ALTER TABLE statement (be sure to replace my COLLATE identifier with the one you found previously): 

ALTER TABLE mytable 
ALTER COLUMN mycolumn VARCHAR(10) COLLATE SQL_Latin1_General_CP1_CI_AS

Conclusion

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