#思路:整体思路其实很简单,就是把要求的数分别求出来,在进行相连即可,就是代码长。 #另外:由于活跃的月份数和天数不分试卷还是联系,所以先把试卷表和练习表union all形成表tb1备用。 with tb1 as (select uid, start_time as a, 1 as b from exam_record union all select uid, submit_time as a, 2 as b from practice_record) select uid, if(aa is null,0,aa) aa, if(bb is null,0,bb) bb, if(cc is ...