mysql - 从三个具有相同 ID 的表中选择

Question

我有三张桌子

students_first_semester_mark (StudentdID,Subject, Semester_I_Mark )
students_second_semester_mark (StudentdID,Subject, Semester_II_Mark )
students_third_semester_mark (StudentdID,Subject, Semester_III_Mark )

我想要以下类型的输出：

_________________________________________________________________________________
|StudentdID  | Subject |  Semester_I_Mark|  Semester_II_Mark |  Semester_III_Mark
_________________________________________________________________________________

请注意Semester_I_MarkorSemester_II_Mark可能有 Null 值。

我渴望得到你的答案。

标签： mysqlsqlselectjoin

Answer 1

以下是我能想到的最简单的答案。

SELECT T1.StudentdID,T1.Subject,T1.Semester_I_Mark,            
       T2.Semester_II_Mark, T3.Semester_III_Mark
FROM students_first_semester_mark T1, students_second_semester_mark T2, 
     students_third_semester_mark T3
JOIN T2 ON T1.StudentdID = T2.StudentdID
JOIN T3 ON T1.StudentdID = T3.StudentdID