今天同事碰到一个SQL的性能问题，主要是MERGE INTO的性能问题，执行脚本的时候，居然耗时50多分钟，汗！简直让人抓狂，脚本如下：
MERGE INTO EDS.TW_DP_B_TDTERM_IMEI_DAY DM
USING T_IMEI_DAY_1111 TEMP
ON(
DM.DATE_CD = TEMP.DATE_CD AND
DM.CITY_ID = TEMP.CITY_ID AND
DM.IMEI = TEMP.IMEI AND
DM.USR_NBR = TEMP.USR_NBR
)
WHEN MATCHED THEN UPDATE SET
DM.GSM_FLUX = TEMP.GSM_FLUX ,
DM.TD_FLUX = TEMP.TD_FLUX ,
DM.GPRS_FLUX = TEMP.GPRS_FLUX
WHEN NOT MATCHED THEN INSERT(