How to Find Out Distinct Records?

Hi,

I want to find out distinct records in my query. Following is the query

SELECT DISTINCT m.client_id,t.Acc_NUM
FROM MST_MASTER m,
MST_TRANS t
WHERE
m.Acc_NUM= t.Acc_NUM
GROUP BY m.client_id,t.Acc_NUM

The Out put i m getting is :
Client_Id Acc_Num
41398 370855082
41398 370855157
41398 370855082

I want distinct records for client_id.

Any hep is appreciated.

Thanks.