Question

我想选择所有通过semester 1 和 4 的学生，我的查询只显示学生一行，我是期待两个人。

SELECT Student.mat_stud, fname, lname, dbirth, materials_notes, semester
FROM Student, Notes 
WHERE Notes.mat_stud = Student.mat_stud
    AND fails_status = 1
    AND Notes.mat_div = 1
    AND semester IN(1 , 4)
    AND Notes.level = 1 
    AND school_year = 2015
Group By Notes.mat_stud
Having count(fname) = 2
Order By Notes.mat_stud

我的数据库表如下所示：

Student
-------------------------
mat_stud    fname   lname
-------------------------
142-3698    fname   name    
142-3699    fname   name        
142-3701    fname   name    
142-3700    fname   name    



Notes
---------------------------------------------------------------
mat_stud    materials_notes     semester    level   school_year
---------------------------------------------------------------
142-3698                        1           1       2015
142-3699                        1           1       2015
142-3701                        1           1       2015
142-3698                        4           1       2015
142-3700                        1           1       2015
142-3700                        4           1       2015

预期结果：

mat_stud    fname   lname   materials_notes     semester
142-3698    fname   name                        1
142-3698    fname   name                        4
142-3700    fname   name                        1
142-3700    fname   name                        4

Answer 1

我通过加入已经过第一学期和第四学期的所有学生的成绩来获得这个解决方案：

SELECT Notes.mat_stud FROM Notes 
    WHERE semester IN (1, 4) Group By mat_stud Having COUNT(*) = 2

与所有学生一起。

SELECT t1.mat_stud, fname, lname, materials_notes FROM Student as t1, Notes 
INNER JOIN ( SELECT Notes.mat_stud FROM Notes 
WHERE semester IN (1, 4) Group By mat_stud Having COUNT(*) = 2) as t2 
ON t2.mat_stud = t1.mat_stud  
WHERE fails_status = 1 
AND Notes.mat_div = 1 
AND Notes.level = 1 
AND school_year = 2015 
AND t1.mat_stud = Notes.mat_stud 
Order By Notes.mat_stud

Answer 2

select S.mat_stud, S.fname, S.lname, N.materials_notes, N.semester
from Notes N, student S 
where N.mat_stud = S.mat_stud and N.mat_stud in (
    select mat_stud from Notes where semester in(1,4) 
    group by mat_stud 
    having count(mat_stud) > 1
)

选择在同一列中具有两个不同值的行

2 个答案: