，LEFT JOIN有关问题，着

在线等，，LEFT JOIN问题，，着急
 SELECT 
                    PC_DESC,
                    NVL(ROUND(CALL_DUR,0),0) AS CALL_DUR,
                    A.LOCALNET
                    FROM
                    APP_THRESHOLD_LOCALPC A
                    LEFT JOIN UN_F_CDR_DPCTRAF_15 B ON A.PC_DESC = B.DPC_DESC
                    AND DAY_ID = 20130904
                    AND HOUR_ID = 8
                    AND MI_ID = 30

 SELECT 
                    PC_DESC,
                    NVL(ROUND(CALL_DUR,0),0) AS CALL_DUR,
                    A.LOCALNET
                    FROM
                    APP_THRESHOLD_LOCALPC A
                    LEFT JOIN UN_F_CDR_DPCTRAF_15 B ON A.PC_DESC = B.DPC_DESC
                    WHERE 1=1
                    AND DAY_ID = 20130904
                    AND HOUR_ID = 8
                    AND MI_ID = 30