Select and insert in same transaction

I am new to SQL. I want to do a query:

	select colA, colB, colC from table
	  where colDate is null

After this, I want to set colDate of each record selected in the above query to the current date.

How can I assure that I update all the selected records from the first query and no more. I am worried that between the two DML statements further records might have been added having colDate = NULL.

TIA - Larry Received on Mon Mar 18 2002 - 15:15:55 CST