写一个查询这个..？

Question

学生和成绩。 Students 包含三列 ID、Name 和 Marks、Grades-(grade,min_mark,max_mark)

Ketty 给 Eve 一个任务来生成一个包含三列的报告：名称、等级和标记。 Ketty 不想要那些成绩低于 8 分的学生的姓名。报告必须按成绩降序排列——即首先输入更高的成绩。如果分配给他们的同一年级 (1-10) 的学生不止一名，请按这些特定学生的姓名字母顺序排列这些学生。最后，如果分数低于 8 分，则使用“NULL”作为他们的名字，并按分数升序排列。

写一个查询来帮助 Eve。

注意 如果成绩小于8，则打印“NULL”作为名称。

我已经写了这个查询：

select name,grade,marks from students s join grades g on marks between min_mark and max_mark
where grade>7
order by 2 desc,name

select translate(name,name,'NULL'),grade,marks from students s join grades g on marks between min_mark and max_mark
where grade<=7
order by 3 desc

但不知道如何加入这两个查询。

Answer 1

大概是这样的：

SELECT CASE WHEN g.grade < 8 THEN NULL ELSE s.name END as name,
    g.grade, s.marks 
FROM students AS s 
INNER JOIN grades AS g 
ON s.marks BETWEEN g.min_mark AND g.max_mark
ORDER BY g.grade DESC, s.name;

Answer 2

SELECT CASE WHEN Grades.Grade < 8 THEN NULL ELSE Students.Name END as name,
   Grades.Grade, Students.Marks 
FROM Students INNER JOIN Grades 
ON Students.Marks BETWEEN Grades.Min_mark AND Grades.Max_mark
ORDER BY Grades.Grade DESC, Students.Name;

Answer 3

select case
when grade < 8 then NULL
else
name
end
as name, grade, marks
from students, grades
where marks between min_mark and max_mark
order by grade desc, name asc, marks asc;

Answer 4

SELECT 
CASE 
    WHEN G.Grade < 8 THEN NULL
    ELSE S.Name
END,
G.Grade, S.Marks
FROM Students AS S
JOIN Grades AS G
ON S.Marks BETWEEN G.Min_Mark AND G.Max_Mark
ORDER BY G.Grade DESC, S.Name ASC;

Answer 5

这是我的回答，但他并不完美： 也许从那，你可以解决

grades.grade, students.marks,
case
    when grades.grade < 8 then "null"
    else students.name
    end as NNN
from students
inner join grades on students.marks between grades.min_mark and grades.max_mark
order by grades.grade desc;

Answer 6

你也可以试试下面的 SQL 查询：

SELECT CASE WHEN (STUDENTS.MARKS < 70) THEN 'NULL' ELSE STUDENTS.NAME END,
        GRADES.GRADE, STUDENTS.MARKS
FROM STUDENTS, GRADES
WHERE STUDENTS.MARKS >= GRADES.MIN_MARK AND STUDENTS.MARKS <= GRADES.MAX_MARK
ORDER BY GRADES.GRADE DESC, STUDENTS.NAME ASC;

或

SELECT CASE WHEN (STUDENTS.MARKS < 70) THEN 'NULL' ELSE STUDENTS.NAME END,
        GRADES.GRADE, STUDENTS.MARKS
FROM STUDENTS, GRADES
WHERE STUDENTS.MARKS BETWEEN GRADES.MIN_MARK AND GRADES.MAX_MARK
ORDER BY GRADES.GRADE DESC, STUDENTS.NAME ASC;

Answer 7

在hackerrank上尝试和测试过的代码...

select s.name, g.grade, s.marks from students s, grades g where g.grade>=8 and s.marks between g.min_mark and g.max_mark order by g.grade desc, s.name;

select 'NULL', g.grade, s.marks from students s, grades g where g.grade<8 and s.marks between g.min_mark and g.max_mark order by g.grade desc, s.marks;

Answer 8

SELECT 

  CASE 
  WHEN marks >= 70 THEN name
  ELSE NULL
  END AS req_name,
 
  CASE
  WHEN marks BETWEEN 0  AND 9  THEN 1
  WHEN marks BETWEEN 10 AND 19 THEN 2
  WHEN marks BETWEEN 20 AND 29 THEN 3
  WHEN marks BETWEEN 30 AND 39 THEN 4
  WHEN marks BETWEEN 40 AND 49 THEN 5
  WHEN marks BETWEEN 50 AND 59 THEN 6
  WHEN marks BETWEEN 60 AND 69 THEN 7
  WHEN marks BETWEEN 70 AND 79 THEN 8
  WHEN marks BETWEEN 80 and 89 THEN 9
  WHEN marks BETWEEN 90 and 100 THEN 10
  END AS grade,
 
  marks
 
FROM students
ORDER BY grade DESC, req_name, marks ASC

Answer 9

这在 MySQL 中对我有用 -

select if(Grade < 8, NULL , Name), Grade, Marks
from Students
Inner Join Grades
where Marks between Min_Mark AND Max_Mark
ORDER BY GRADE DESC, Name ASC;

Answer 10

这个答案不像以前的答案那么优雅，而是我如何拼凑出一个解决方案。 看到这里的解决方案后，我建议使用 JOIN、ON 和 BETWEEN 语句而不是我的解决方案，我使用最左边的字符并添加一个以使其与我在第二个表中看到的值对齐。 如果您在我上面提到的之外发现任何缺陷，请发表评论，以便我改进。

SELECT 
CASE 
    WHEN LEFT(MARKS, 1) + 1 < 8 AND MARKS != 100 THEN NULL
    ELSE NAME
END AS NAME, 
CASE 
    WHEN MARKS = 100 THEN 10
    ELSE LEFT(MARKS, 1) + 1
END AS GRADE, MARKS 
FROM STUDENTS
ORDER BY GRADE DESC,
(CASE WHEN GRADE >= 8 THEN NAME END),
(CASE WHEN GRADE < 8 THEN MARKS END) ASC