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一道数据库的面试题求解
1--就拿你问题2的数据举例，邮箱和name同时重复，只保留其中一条delete from 表名 where id not in (select min(id) from 表名 group by name,email) 2--select t1.* from 表名 t1,(select name,max(lastlogon) lastlogon from 表名 group by name) t2where t1.name=t2.name and t1.lastlogon=t2.lastlogon
问几题数据库面试题++++++++++++++++++
14: Cselect e.ename form emp e where e.empno not in (select m.mgr from emp m)1: 1)select A.sid, S.sname from(select sid from sc where cid in (select cid from sc where sid = 123456)group by sid having count(*) = (select count(*) from sc where sid = 123456)) as A inner join student as S on A.sid = S.sid2)select sc.cid, s.sname, sc.cid, c.cname, sc.scscore from sc, student as s, course as cwhere s.sid = sc.sid and c.cid = sc.cid and sc.sid in(select sc.sid from sc,(select cid, avg(scscore) as avg_score from sc group by cid) as awhere sc.cid = a.cid and sc.scscore 《 a.avg_scoregroup by sc.sid having count(*) 》 2)1:select 日期字段,sum(case when 胜负字段 = ’胜’ then 1 else 0 end) as from 比赛表group by 日期字段
