Trouble updating new column after adding it

Question

Given the following SQL:

IF EXISTS (SELECT * FROM sys.columns WHERE name = 'NewFieldName' AND object_id = OBJECT_ID('dbo.MyTableName'))
    RETURN

-- Add NewFieldName column to part of the Summer 2012 release cycle.
ALTER TABLE dbo.[MyTableName] ADD
    [NewFieldName] SmallINT NOT NULL
        CONSTRAINT DF_MyTableName_NewFieldName DEFAULT (2)

UPDATE [MyTableName] SET NewFieldName = 1 WHERE [Name] = 'FindMe' --Update one specific value

Produces the following error message:

Msg 207, Level 16, State 1, Line 10 Invalid column name 'NewFieldName'.

I'm sure I'm missing something basic, but trying to put "GO" after the alter makes the UPDATE run everytime and I don't want to do that.

How can I structure this statement so that it will check to see if the column exists and, if it doesn't add it and then set the values as stated in my UPDATE statements?

Answer 1

You need the statement referencing the new column to be compiled after the new column is added. One way of doing this is to run it as a child batch with EXEC.

IF NOT EXISTS (SELECT * 
               FROM   sys.columns 
               WHERE  name = 'NewFieldName' 
                      AND object_id = OBJECT_ID('dbo.MyTableName')) 
BEGIN
  -- Add NewFieldName column to part of the Summer 2012 release cycle. 
  ALTER TABLE dbo.[MyTableName] 
           ADD [NewFieldName] SMALLINT NOT NULL 
           CONSTRAINT DF_MyTableName_NewFieldName DEFAULT (2) 

  EXEC(' UPDATE [MyTableName] SET NewFieldName = 1 WHERE [Name] = ''FindMe''') 
END

The reason it worked for you originally is presumably because the table itself did not exist when the batch was compiled thus meaning that all statements in it referencing the table are subject to deferred compile.