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Asked: 2026-05-13T17:49:20+00:00

Ok, i know CONCAT_NULL_YIELDS_NULL will always be set to ON in future versions of

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Ok, i know CONCAT_NULL_YIELDS_NULL will always be set to ON in future versions of SQL (insert MSDN search params(yadda,yadda)) so bear with me.

Boring details: The platform is MSSQL 2000 Enterprise (v8 sp4) AKA Critatious Period Edition.

The following will evaluate to NULL

SELECT 'abc' + NULL;

Understandable. But you can circumvent this with the following:

SET CONCAT_NULL_YIELDS_NULL OFF;
SELECT 'abc' + NULL;

In which case the result is “abc”. From here on, future sql statements will allow concatenation with NULL. But is this a ‘persistent’ runtime setting? Such as, is this setting only applied for my session to the SQL server, or does it apply to statements executed by all users?

As far as i can tell, after setting _YIELDS_NULL to ON, a restart to the MSSQL services will have it default back to OFF (correct me if i’m wrong).

Last thing: I’m not actually planning to put this into practice. A third-party stored procedure failed (looks like they might have updated it, breaking it). Best i can figure is that they implemented it with the assumption that “SET CONCAT_NULL_YIELDS_NULL” was set to ON. And it used to always work.

I’m just looking for a cause: Is there a way to have CONCAT_NULL_YIELDS_NULL set to ON upon SQL server startup?

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1 Answer

  1. Editorial Team

    CONCAT_NULL_YIELDS_NULL can be set:

    • per connection – when you close connection and open new, it’s back to default

    • per database

      • open Microsoft SQL Server Management Studio, rightclick your database and select properties. It’s in the Miscellaneous section.

    • or from T-SQL

      ALTER DATABASE database_name SET { CONCAT_NULL_YIELDS_NULL OFF }

    Note: some clients can issue set concat_null_yields_null on command when opening connection. For example SQL Server Management Studio connecting to SQL 2005 does.
    Use SQL Server Profiller to find about your connection.

    I do not have SQL 2000 on my notebook to test exactly on that version.

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