Here's what I'd do next (assumes you have primary key on the source table):

[font="Courier New"]CREATE TABLE logins

   (

   pk datatype,

   lastlogon bigint

   )

INSERT INTO logins

   SELECT TOP 50%

       A.pk,

       A.laslogon

   FROM

       TABLE A LEFT JOIN

       logins L ON

           A.pk = L.pk

   WHERE

       L.pk IS NULL

SELECT

   lastlogon

FROM

   TABLE

WHERE

   ISNUMERIC(lastlogon) <> 0[/font]