[sql] Alter user defined type in SQL Server

there's a good example of a more comprehensive script here

It's worth noting that this script will include views if you have any. I ran it and instead of exec'ing inline generated a script as the output which I then tweaked and ran.

Also, if you have functions/sprocs using the user defeined types you'll need to drop those before running your script.

Lesson Learned: in future, don't bother with UDTs they're more hassle than they're worth.

SET NOCOUNT ON

DECLARE @udt VARCHAR(150)
DECLARE @udtschema VARCHAR(150)
DECLARE @newudtschema VARCHAR(150)
DECLARE @newudtDataType VARCHAR(150)
DECLARE @newudtDataSize smallint
DECLARE @OtherParameter VARCHAR(50)

SET @udt = 'Name' -- Existing UDDT
SET @udtschema = 'dbo' -- Schema of the UDDT
SET @newudtDataType = 'varchar' -- Data type for te new UDDT
SET @newudtDataSize = 500 -- Lenght of the new UDDT
SET @newudtschema = 'dbo' -- Schema of the new UDDT
SET @OtherParameter = ' NULL' -- Other parameters like NULL , NOT NULL
DECLARE @Datatype VARCHAR(50),
    @Datasize SMALLINT

DECLARE @varcharDataType VARCHAR(50)

DECLARE @Schemaname VARCHAR(50),
    @TableName VARCHAR(50),
    @FiledName VARCHAR(50)

CREATE TABLE #udtflds
    (
      Schemaname VARCHAR(50),
      TableName VARCHAR(50),
      FiledName VARCHAR(50)
    )

SELECT TOP 1
        @Datatype = Data_type,
        @Datasize = character_maximum_length
FROM    INFORMATION_SCHEMA.COLUMNS
WHERE   Domain_name = @udt
        AND Domain_schema = @udtschema

SET @varcharDataType = @Datatype
IF @DataType Like '%char%'
    AND @Datasize IS NOT NULL
    AND ( @newudtDataType <> 'varchar(max)'
          OR @newudtDataType <> 'nvarchar(max)'
        )
    BEGIN
        SET @varcharDataType = @varcharDataType + '('
            + CAST(@Datasize AS VARCHAR(50)) + ')'
    END

INSERT  INTO #udtflds
        SELECT  TABLE_SCHEMA,
                TABLE_NAME,
                Column_Name
        FROM    INFORMATION_SCHEMA.COLUMNS
        WHERE   Domain_name = @udt
                AND Domain_schema = @udtschema

DECLARE @exec VARCHAR(500)

DECLARE alter_cursor CURSOR
    FOR SELECT  Schemaname,
                TableName,
                FiledName
        FROM    #udtflds

OPEN alter_cursor
FETCH NEXT FROM alter_cursor INTO @Schemaname, @TableName, @FiledName

WHILE @@FETCH_STATUS = 0
    BEGIN
        SET @exec = 'Alter Table ' + @Schemaname + '.' + @TableName
            + '  ALTER COLUMN ' + @FiledName + ' ' + @varcharDataType
        EXECUTE ( @exec
               )
        FETCH NEXT FROM alter_cursor INTO @Schemaname, @TableName, @FiledName

    END

CLOSE alter_cursor

SET @exec = 'DROP TYPE [' + @udtschema + '].[' + @udt + ']'
EXEC ( @exec
    )

SET @varcharDataType = @newudtDataType

IF @newudtDataType Like '%char%'
    AND @newudtDataSize IS NOT NULL
    AND ( @newudtDataType <> 'varchar(max)'
          OR @newudtDataType <> 'nvarchar(max)'
        )
    BEGIN
        SET @varcharDataType = @varcharDataType + '('
            + CAST(@newudtDataSize AS VARCHAR(50)) + ')'
    END

SET @exec = 'CREATE TYPE [' + @newudtschema + '].[' + @udt + '] FROM '
    + @varcharDataType + ' ' + @OtherParameter
EXEC ( @exec
    )

OPEN alter_cursor
FETCH NEXT FROM alter_cursor INTO @Schemaname, @TableName, @FiledName

WHILE @@FETCH_STATUS = 0
    BEGIN
        SET @exec = 'Alter Table ' + @Schemaname + '.' + @TableName
            + '  ALTER COLUMN ' + @FiledName + ' ' + '[' + @newudtschema
            + '].[' + @udt + ']'
        EXECUTE ( @exec
               )
        FETCH NEXT FROM alter_cursor INTO @Schemaname, @TableName, @FiledName
    END

CLOSE alter_cursor
DEALLOCATE alter_cursor
SELECT  *
FROM    #udtflds

DROP TABLE #udtflds

1: http://www.sql-server-performance.com/2008/how-to-alter-a-uddt/ has replaced http://www.sql-server-performance.com/faq/How_to_alter_a%20_UDDT_p1.aspx