坚持查询。我想要每个董事会的学生总数

Question

我有两张桌子学生和成绩 它们通过PK FK关系从学生（计数）链接到等级（marksID）。 董事会明智的我必须选择得分超过70％的学生百分比 每个城市都有自己的董事会 查询是：

select g3.board,(count(g2.percentag)/ count(board))*100
from  loadbise.grade as g2, loadbise.student as g3
where g2.marksID=g3.countt
and percentag > 70
group by g3.board;

我知道count（ge.percentag）和count（board）的值是相同的 我被困在这个数量（板）点 我希望每个董事会的学生总人数（董事会） 我错过了什么？ 架构是..

Answer 1

检查此SQL查询。对于每个董事会，我已经计算了百分比≥1的学生数量。 70和学生总数。

SELECT T.board,
       (SELECT COUNT(DISTINCT G.countt) FROM loadbise.Grades AS G
            JOIN loadbise.Student AS S ON S.countt = G.countt
        WHERE G.percentage > 70
                  AND S.board = T.board)
        /
       (SELECT COUNT(S.countt) FROM loadbise.Student AS S
        WHERE S.board = T.board) * 100
FROM
    (SELECT DISTINCT board
    FROM Student AS S) AS T