Question

I need to update the DateModified Column without knowing the name of the Primary Key Column.

Basically, I’ve got a plain-jane UPDATE trigger like this:

CREATE TRIGGER updated_SCHEMA_TABLE
 ON [SCHEMA].[TABLE]
   AFTER UPDATE AS 
     BEGIN 
       SET NOCOUNT ON; 
       UPDATE [SCHEMA].[TABLE] 
       SET DateModified = getdate() 
       WHERE [PRIMARYKEY]
       IN (SELECT [PRIMARYKEY]
       FROM Inserted)
     END

but won’t know the primary key’s column name because the trigger will be generated programmatically (see this question as to why).

Is this possible?

Answer 1

OK, perhaps I was a bit unfair leaving this part as an “exercise” in the previous question.

This would work for tables with a single column PK. It might be easiest to start with these and then go back and manually adjust those with a composite PK.

select 'create trigger updated_'+s.name + '_' + t.name + ' on  ' + quotename(s.name) + '.' + quotename(t.name) 
       + ' after update as'
       + ' begin '
       + ' set nocount on; '
       + ' update t'
       + '     set [DateModified] = getdate()'
       + '     from inserted i'
       + '         inner join ' + quotename(s.name) + '.' + quotename(t.name) + ' t'
       + '             on i.' + quotename(c2.name) + ' = t.' + quotename(c2.name)
       + ' end'
    from sys.columns c
        inner join sys.tables t
            on c.object_id = t.object_id
        inner join sys.schemas s
            on t.schema_id = s.schema_id
        inner join sys.indexes i
            on t.object_id = i.object_id
        inner join sys.index_columns ic
            on i.object_id = ic.object_id
                and i.index_id = ic.index_id
        inner join sys.columns c2
            on ic.object_id = c2.object_id
                and ic.index_id = c2.column_id
    where c.name = 'DateModified'
        and t.type = 'U'
        and i.is_primary_key = 1