从表中选择一个字段具有相同值的行 [英] Selecting rows from a table that have the same value for one field

问题描述

我有一个带有以下两个表的MySQL数据库:

I have a MySQL database with these two tables:

Tutor(tutorId, initials, lastName, email, phone, office)
Student(studentId, initials, lastName, email, tutorId)

要查询共享同一位导师的任何学生的姓名缩写和姓氏是什么?

What is the query to return the initials and last names of any student who share the same tutor?

我尝试了SELECT intials, lastName FROM Student WHERE tutorId = tutorId，但这只是返回所有学生的姓名.

I tried SELECT intials, lastName FROM Student WHERE tutorId = tutorId but that just returns the names of all students.

推荐答案

您将不得不与学生对抗:

You'll have to join students against itself:

SELECT s1.initials, s1.lastName
FROM Student s1, Student s2
WHERE s1.studentId <> s2.studentID /* Every student has the same tutor as himself */
AND s1.tutorId = s2.tutorid

如果要输出对:

SELECT s1.initials, s1.lastName, s2.initials, s2.lastName
FROM Student s1, Student s2
WHERE s1.studentId <> s2.studentID /* Every student has the same tutor as himself */
AND s1.tutorId = s2.tutorid

要获取教师列表-学生:

To get a list of Tutor - Students:

SELECT tutorId, GROUP_CONCAT( initials, lastName SEPARATOR ', ') 
FROM `Student` 
GROUP BY tutorId
/* to only show tutors that have more than 1 student: */
/* HAVING COUNT(studentid) > 1 */

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