统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

    1. SELECT
    2.     a.c_id, a.c_name,
    3.   SUM(CASE WHEN s_score >85 AND s_score <= 100 THEN 1 ELSE 0 END) "[100-85]",
    4.   SUM(CASE WHEN s_score >70 AND s_score <= 85 THEN 1 ELSE 0 END) "[85-70]",
    5.   SUM(CASE WHEN s_score >60 AND s_score <=70 THEN 1 ELSE 0 END) "[70-60]",
    6.   SUM(CASE WHEN s_score >0 AND s_score <=60 THEN 1 ELSE 0 END) "[0-60]",
    7.   sum(case when s_score >85 and s_score <=100 then 1 else 0 end)/ count(1) "[100-85]%",
    8.     sum(case when s_score >70 and s_score <=85 then 1 else 0 end)/ count(1) "[85-70]%",
    9.     sum(case when s_score >60 and s_score <=70 then 1 else 0 end)/ count(1) "[70-60]%",
    10.     sum(case when s_score >0 and s_score <=60 then 1 else 0 end)/ count(1) "[0-60]%"
    11. FROM
    12.     Course a
    13. LEFT JOIN
    14.     Score b
    15. ON a.c_id = b.c_id
    16. GROUP BY a.c_id, a.c_name