整数范围上的Oracle SQL组

使用oracle11g

我有一张表格，里面有学生ID和分数的列表。另一个查找表保存每个坡率的边界值

STUDENT_MARKS:
STUDENT_ID  STUDENT_MARK
   1            20
   2            60
   3            90
   4            20

GRADE_LOOKUP:
GRADE_ID    GRADE   LOWER_MARK  UPPER_MARK
  1           A         80         100
  2           B         50          79
  3           C          0          49

我试图写一个查询，返回每个年级边界的学生数量。例如：

STUDENT_GRADE   STUDENT_COUNT
  A                  1
  B                  1
  C                  2

我编写了以下代码，返回正确的结果，但是实际数据包含大约40个“等级”边界。因此，下面的代码变得相当笨拙。理想情况下，我正在寻找一种方法，使用一种内置的方法，按照团队的思路，产生相同的结果

SELECT  'A'               AS STUDENT_GRADE,
        COUNT(STUDENT_ID) AS STUDENT_COUNT
FROM STUDENT_MARKS
WHERE STUDENT_MARK >= (SELECT LOWER_MARK FROM GRADE_LOOKUP WHERE GRADE_ID 
                       = 1)
UNION ALL
SELECT  'B'               AS STUDENT_GRADE,
        COUNT(STUDENT_ID) AS STUDENT_COUNT
FROM STUDENT_MARKS
WHERE STUDENT_MARK >= (SELECT LOWER_MARK FROM GRADE_LOOKUP WHERE GRADE_ID 
                       = 2)
AND STUDENT_MARK <= (SELECT UPPER_MARK FROM GRADE_LOOKUP WHERE GRADE_ID 
                     =2)
UNION ALL
SELECT  'C'               AS STUDENT_GRADE,
        COUNT(STUDENT_ID) AS STUDENT_COUNT
FROM STUDENT_MARKS
WHERE STUDENT_MARK <= (SELECT UPPER_MARK FROM GRADE_LOOKUP WHERE GRADE_ID 
                       = 3);

---

嗯？只需执行一个join和

分组操作

：

SELECT gl.GRADE, COUNT(*) AS STUDENT_COUNT
FROM STUDENT_MARKS sm JOIN
     GRADE_LOOKUP gl
     ON sm.student_mark BETWEEN gl.LOWER_MAKR and gl.UPPER_MARK
GROUP BY gl.GRAdE
ORDER BY gl.GRADE;

SELECT gl.GRADE, COUNT(*) AS STUDENT_COUNT
FROM STUDENT_MARKS sm JOIN
     GRADE_LOOKUP gl
     ON sm.student_mark BETWEEN gl.LOWER_MAKR and gl.UPPER_MARK
GROUP BY gl.GRAdE
ORDER BY gl.GRADE;