我一直在獲取連接表上的SUM時(shí)總是遇到麻煩，總是有一個(gè)問題，我可以通過運(yùn)行兩個(gè)查詢來獲得所需的結(jié)果，我想知道這兩個(gè)查詢是否可以組合在一起以構(gòu)成一個(gè)連接查詢，這是我查詢的結(jié)果有和我嘗試加入查詢查詢1SELECT last_name, first_name, DATE_FORMAT( (mil_date),  '%m/%d/%y' ) AS dates, SUM( drive_time ) MINUTES FROM bhds_mileage LEFT JOIN bhds_teachers i ON i.ds_id = bhds_mileage.ds_id WHERE mil_date BETWEEN  '2016-04-11' AND  '2016-04-30'AND bhds_mileage.ds_id =5GROUP BY CONCAT( YEAR( mil_date ) ,  '/', WEEK( mil_date ) ) ,    bhds_mileage.ds_idORDER BY last_name ASC , dates ASC 以分鐘為單位的輸出是271、281、279查詢2SELECT last_name, first_name, DATE_FORMAT((tm_date), '%m/%d/%y') AS dates,   SUM(tm_hours) total FROM bhds_timecard LEFT JOIN bhds_teachers i ON i.ds_id = bhds_timecard.ds_id WHERE tm_date BETWEEN '2016-04-11' AND '2016-04-30' AND bhds_timecard.ds_id = 5GROUP BY CONCAT(YEAR(tm_date), '/', WEEK(tm_date)), bhds_timecard.ds_id ORDER BY last_name ASC, dates ASC這里的輸出是33.00，36.00，26.75現(xiàn)在我嘗試加入查詢SELECT last_name, first_name, DATE_FORMAT((tm_date), '%m/%d/%y') AS dates,  SUM(tm_hours) total,  SUM( drive_time ) MINUTES FROM bhds_timecard LEFT JOIN bhds_teachers i ON i.ds_id = bhds_timecard.ds_id LEFT JOIN bhds_mileage ON DATE_FORMAT((bhds_timecard.tm_date), '%m/%d/%y') = DATE_FORMAT((bhds_mileage.mil_date), '%m/%d/%y') AND bhds_timecard.ds_id = bhds_mileage.ds_idWHERE tm_date BETWEEN '2016-04-11' AND '2016-04-30' AND bhds_timecard.ds_id = 5GROUP BY CONCAT(YEAR(tm_date), '/', WEEK(tm_date)), bhds_timecard.ds_id 括號(hào)是預(yù)期的這輸出1044（271），1086（281），1215（279）