[ @msgnum = ] msg_id

Is the ID of the message. msg_id is int with a default of NULL. msg_id for user-defined error messages can be an integer between 50,001 and 2,147,483,647. The combination of msg_id and language must be unique; an error is returned if the ID already exists for the specified language.

[ @severity = ] severity

Is the severity level of the error. severity is smallint with a default of NULL. Valid levels are from 1 through 25. For more information about severities, see Database Engine Error Severities.

[ @msgtext = ] 'msg'

Is the text of the error message. msg is nvarchar(255) with a default of NULL.

[ @lang = ] 'language'

Is the language for this message. language is sysname with a default of NULL. Because multiple languages can be installed on the same server, language specifies the language in which each message is written. When language is omitted, the language is the default language for the session.

[ @with_log = ] { 'TRUE' | 'FALSE' }

Is whether the message is to be written to the Windows application log when it occurs. @with_log is varchar(5) with a default of FALSE. If TRUE, the error is always written to the Windows application log. If FALSE, the error is not always written to the Windows application log but can be written, depending on how the error was raised. Only members of the sysadmin server role can use this option.

Note:
If a message is written to the Windows application log, it is also written to the Database Engine error log file.

[ @replace = ] 'replace'

If specified as the string replace, an existing error message is overwritten with new message text and severity level. replace is varchar(7) with a default of NULL. This option must be specified if msg_id already exists. If you replace a U.S. English message, the severity level is replaced for all messages in all other languages that have the same msg_id.

0 (success) or 1 (failure)

None

For non-English versions of SQL Server, the U.S. English version of a message must already exist before the message can be added using another language. The severity of the two versions of the message must match.

When localizing messages that contain parameters, use parameter numbers that correspond to the parameters in the original message. Insert an exclamation point (!) after each parameter number.

Because of language syntax differences, the parameter numbers in the localized message may not occur in the same sequence as in the original message.

Requires membership in the sysadmin and serveradmin fixed server roles.

A. Defining a custom message

USE master
GO
EXEC sp_addmessage 50001, 16, 
   N'Percentage expects a value between 20 and 100. 
   Please reexecute with a more appropriate value.';
GO

B. Adding a message in two languages

USE master;
GO
EXEC sp_addmessage @msgnum = 60000, @severity = 16, 
   @msgtext = N'The item named %s already exists in %s.', 
   @lang = 'us_english';

EXEC sp_addmessage @msgnum = 60000, @severity = 16, 
   @msgtext = N'L''élément nommé %1! existe déjà dans %2!', 
   @lang = 'French';
GO

C. Changing the order of parameters

USE master;
GO

EXEC sp_addmessage 
    @msgnum = 60000, 
    @severity = 16,
    @msgtext = 
        N'This is a test message with one numeric
        parameter (%d), one string parameter (%s), 
        and another string parameter (%s).',
    @lang = 'us_english';

EXEC sp_addmessage 
    @msgnum = 60000, 
    @severity = 16,
    @msgtext = 
        -- In the localized version of the message,
        -- the parameter order has changed. The 
        -- string parameters are first and second
        -- place in the message, and the numeric 
        -- parameter is third place.
        N'Dies ist eine Testmeldung mit einem 
        Zeichenfolgenparameter (%3!),
        einem weiteren Zeichenfolgenparameter (%2!), 
        und einem numerischen Parameter (%1!).',
    @lang = 'German';
GO  

-- Changing the session language to use the U.S. English
-- version of the error message.
SET LANGUAGE us_english;
GO

RAISERROR(60000,1,1,15,'param1','param2') -- error, severity, state,
GO                                       -- parameters.

-- Changing the session language to use the German
-- version of the error message.
SET LANGUAGE German;
GO

RAISERROR(60000,1,1,15,'param1','param2') -- error, severity, state, 
GO                                       -- parameters.

Reference

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