sql query Negative values assign 0 in case using

Question

Hi 

My sql query  is below

 

SELECT (SUM(CAST(TOTAL_TRIPS_SLUM AS BIGINT)) - SUM(CAST(SLUM_SUPPLY AS BIGINT))) as Balance  FROM TBL_SMS_REPORT

WHERE date= '2015-09-01' 

 

Out put is :

-9

 

 i need negative values 0 assign how  this write the commant.