Invalid lookup override

Problem :
LOOKUP transformation : SQL Override
SELECT DISTINCT TIM_DT_ID FROM L_TIM_DT
WHERE TIM_DT_ID >= '2006-01-01'

Error :
Severity Timestamp Node Thread Message Code Message
WARNING 3/6/2008 18:12:23 node01_quadjt MAPPING DBG_21263 Invalid lookup override

Solved :
while overriding the lookup you must have to give the
alias name as exisiting port name,

SELECT DISTINCT L_TIM_DT.TIM_DT_ID as TIM_DT_ID FROM L_TIM_DT
WHERE L_TIM_DT.TIM_DT_ID >= '2006-01-01'