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select sname , avg(scgrade) as 'ƽ¾ù³É¼¨'
from s

join sc on s.sno = sc.sno
where sc.sno in

£¨ select sno from sc

where scgrade <60

group by sno

having count£¨*£©>=2

£©;

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SQL code:
select SNO,avg(isnull(score,0))
from SC
where SNO in (select SNO from SC where score <60 group by SNO having count(*)>=2)group by SNO;

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SQL code:
select S.SNAME,avg(isnull(SC.score,0))
from SC
JOIN S ON SC.SNO=S.SNO
where SC.SNO in (select SNO from SC where score <60 group by SNO having count(*)&