摘要:
简介 select user.id, user.name,t.grade_sum from ( select user_id,sum(grade_num) as grade_sum from grade_info group by user_id having grade_sum = ( selec
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摘要:
简介 联表查询, 相当于 inner join? 不是 因为不能用on select a.id, a.number, count(distinct b.number) as t_rank from passing_number as a, passing_number as b where a.nu
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摘要:
简介 第二个select一定要起一个别名,否则会出错 注意子查询 select a.id, a.job, a.score from grade as a left join ( select job, avg(c.score) as score from grade as c group by c.
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