Weird query results

Hi Experts,
I am trying to figure out a strange Access/SQL behavior as follows.
I have a query that when displaying only 1 column it gives me one quantity of records and when displaying 2 columns it gives me a different qty.
Query1

SELECT DISTINCT TmpPatBillingCodes.PatientsID, #12/31/2013# AS Expr1
FROM TmpPatBillingCodes
WHERE (((#12/31/2013#) Between [effectivefrom] And [end]));

Select allOpen in new window

Query2

SELECT DISTINCT TmpPatBillingCodes.PatientsID, #12/31/2013# AS Expr1, TmpPatBillingCodes.EffectiveFrom
FROM TmpPatBillingCodes
WHERE (((#12/31/2013#) Between [effectivefrom] And [end]));

Select allOpen in new window

Can someone help me figure out?