求解一个mysql数据库查询问题

答案：这段sql是根据要求分段：
select case
 when a>100 then 30
 when a>50 and a<=100 then 20
 when a>0 and a<=50 then 10
 when a=0 then 0
end as a,case
 when b>10 then 30
 when b>5 and b<=10 then 20
 when b>0 and b<=5 then 10
 when b=0 then 0
end as b,case
 when c>3 then 30
 when c>1 and c<=3 then 20
 when c>0 and c<=1 then 10
 when c=0 then 0
end as c
from score
之后就是将分段了的结果，取和就是了 
至于最后的sql，你可以复制上去试一下，应该可以达到你的需求：
select a,b,c,(aaa+bbb+ccc) as 总分 from
(select a,b,c,case
 when a>100 then 30
 when a>50 and a<=100 then 20
 when a>0 and a<=50 then 10
 when a=0 then 0
end as aaa,case
 when b>10 then 30
 when b>5 and b<=10 then 20
 when b>0 and b<=5 then 10
 when b=0 then 0
end as bbb,case
 when c>3 then 30
 when c>1 and c<=3 then 20
 when c>0 and c<=1 then 10
 when c=0 then 0
end as ccc
from score) as books

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