Using UDF for default value of a column

I created a UDF that I am using to generate a default value for a column. It works开发者_如何学Python great, but I want to pass another field as a parameter into the function. Is this possible?

For example, one of the fields is a DealerID field, and I want to pass in the value of the DealerID field into my UDF because I will use it to calculate the new value. Any help would be appreciated!

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No, because the default value will be needed before DealerID is known (eg on INSERT)

Edit:

This means that SQL Server does not the value in the table at the time of insert, only after. Therefore, it can not a UDF for the default.

For example, what about a multiple row insert, or where you have NEWID() default?

Now, using logic basic on DealerID: if it's GUID, why? It's an internal, non-user readable value.

If you really need this, you'll have to use a computed column for the "base" value and another column for the "actual" value with ISNULL.

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I had a similar issue where I wanted to automatically assign a URL slug for new records inserted to the table. The approach I took was to set the field's default value to 'NOTSET' (just a text placeholder value) then used an insert trigger to update the field ON INSERT to the value of my UDF (where the field value is NOTSET) as follows:

CREATE TRIGGER [dbo].[TR_MyTable_MyTriggerName] 
   ON  [dbo].[tblMyTable]
   AFTER INSERT
AS 
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Create the geography field from the lat and lon coordinates
    UPDATE tblMyTable
    SET fldURLSlug = dbo.UDF_MyFunction(INS.[fldRecordTitle])
    FROM tblMyTable MT INNER JOIN inserted INS ON MT.fldRecordId = INS.fldRecordId
    WHERE INS.fldURLSlug = 'NOTSET'

END

GO

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Please correct me if you have a specific reason why you need to use a UDF, but why not just define the default value for the column in your table DDL, which will then be overwritten if you supply a specific value in your UPDATE, INSERT etc.? Using a UDF in a SELECT will cause the function to be executed every row, an overhead you will save if it is taken care of at the table definition level.