Question

How do I need to write my SQL script to ensure my new column is visible on following lines after it is created.

This is the general form of my SQL:

BEGIN TRANSACTION

  if (not exists(select 1 from THIS_TABLE))
      BEGIN
        ALTER TABLE THIS_TABLE add THIS_COLUMN int
      END
COMMIT

BEGIN TRANSACTION

    IF (NOT EXISTS (SELECT 1 FROM THIS_TABLE
            WHERE THIS_COLUMN = 1))
    BEGIN
            UPDATE THIS_TABLE SET THIS_COLUMN = 1 
    END

COMMIT

This is the error I’m getting:

Invalid column name 'THIS_COLUMN'. 

on this line:

        IF (NOT EXISTS (SELECT 1 FROM THIS_TABLE
            WHERE THIS_COLUMN = 1))

Answer 1

The column has to be created before a query that uses it can be parsed. You can accomplish this by putting the update in a different batch, using the “go” keyword:

alter table t1 add c1 int
go
update t1 set c1 = 1

Or by running the second transaction as dynamic SQL:

alter table t1 add c1 int
exec ('update t1 set c1 = 1')