I have a MySQL database with these two tables:
Tutor(tutorId, initials, lastName, email, phone, office)
Student(studentId, initials, lastName, email, tutorId)
What is the query to return the initials and last names of any student who share the same tutor?
I tried SELECT intials, lastName FROM Student WHERE tutorId = tutorId but that just returns the names of all students.
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
If you want to output the pairs:
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
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 */
SELECT Tutor.tutorId, Student.initials, Student.lastName FROM Student INNER JOIN Tutor ON Tutor.tutorId = Student.tutorId GROUP BY tutorId
This will return (not tested, but it should) a list of student initials and last names grouped by tutorId. Is that what you want?
Join Student table to itself
SELECT S1.intials, S1.lastName
FROM Student S1, Student S2
WHERE S1.tutorId = S2.tutorId
AND S1.studentId <> S2.studentId
this is the query in SQL Server, im sure the idea is very close to mySql:
select s1.initials,s1.lastname,s2.initials,s2.lastname from students s1 inner join students s2 on s1.tutorid= s2.tutorid and s1.studentid <> s2.studentid
You will have to make a query for every single tutorId. Pseudo-Code:
for id in tutorIds
query('SELECT intials, lastName FROM Student WHERE tutorId = '+id )
If you wanna have a list containing all Tutors who actually have students, do a
SELECT tutorId FROM Student GROUP BY tutorId
