24 November 2021 MS SQL Server Robert Muehsig

This week I deployed a new feature and tried it on different SQL databases and was a bit suprised that on one database this error message came up:

Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation.

This was strange, because - at least in theory - all databases have the same schema and I was sure that each database had the same collation setting.

Collations on columns

Well… my theory was wrong and this SQL statement told me that “some” columns had a different collation.

select sc.name, sc.collation_name from sys.columns sc
inner join sys.tables t on sc.object_id=t.object_id
where t.name='TABLENAME'

As it turns out, some columns had the collation Latin1_General_CI_AS and some had SQL_Latin1_General_CP1_CI_AS. I’m still not sure why, but I needed to do something.

How to change the collation

To change the collation you can execute something like this:

ALTER TABLE MyTable
ALTER COLUMN [MyColumn] NVARCHAR(200) COLLATE SQL_Latin1_General_CP1_CI_AS

Unfortunately there are restrictions and you can’t change the collation if the column is referenced by any one of the following:

  • A computed column
  • An index
  • Distribution statistics, either generated automatically or by the CREATE STATISTICS statement
  • A CHECK constraint
  • A FOREIGN KEY constraint

Be aware: If you are not in control of the collation or if the collation is “fine” and you want to do this operation anyway, there might be a way to specify the collation in the SQL query.

For more information you might want to check out this Microsoft Docs “Set or Change the Column Collation

Hope this helps!


Written by Robert Muehsig

Software Developer - from Dresden, Germany, now living & working in Switzerland. Microsoft MVP & Web Geek.
Other Projects: KnowYourStack.com | ExpensiveMeeting | EinKofferVollerReisen.de

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