qq_34239939的博客

insert into jwc(st_num,info) value('131141','{"数学":[95,4],"英语":{"英语上":[87,3],"英语下":[82,3]}，"体育":"不及格"}')

更新一张表中的某些记录值，更新条件来自另一张表(数据量大)，效率极其低下。update A set A.a = 0 where A.b in( select distinct B.b from B where B.c = 0);优化后 update A set A.a = 0 where A.b in ( select b from (select distinct B....