I have one table that contains both students and parents records. There is a common field (email address) in both parent and student records that match the records (parents and students have the same email address).
I want my query to find the common email addresses and return each
student record but it must also include a field (Mifare) from the
parents record.
So I have tried to join and where clauses but i am getting crazy results. I was also thinking of using the with clause.
Expected result is
The basic script is:
Select extid, first_name, last_name, commonemail, designation,mifare
from students
Please assist with a basic coding - no procedures etc...just simple help for a newbie!
Thank you all!
Here is the solution for your problem:
SELECT stud.ExtId,
stud.FirstName,
stud.LastName,
stud.CommonEmail,
stud.Designation,
stud.Mifare,
prnt.Mifare
FROM Students AS stud
INNER JOIN Students AS prnt
ON stud.CommonEmail = prnt.CommonEmail
AND stud.Designation = 'Student'
AND prnt.Designation = 'Parent'
You can also follow the link to the demo:
http://sqlfiddle.com/#!9/5b790b/1
Select s.*
p.mifare
from students s
left join students p on p.commonemail=s.commonemail and p.Designation='Parent'
Try using the following Sub query
Select *,
(Select Mifare from students b where b.Designation = 'Parent' and b.commonemail = a.commonemail) as ParentMifare
from students a
I am not sure you can try this way join both the tables with email select only the designation student only.
Select
st.extid,
st.first_name,
st.last_name,
st.commonemail,
st.designation,
st. mifare
pr.parentmifare
from students st inner join students pr on st.commonemail=pr.commonemail
where pr.designation='student' and st.designation='parent'
Related
So I have a database and I have 4 tables (admin, appointment, doctor, patient).
I only care about appointment, doctor and patient.
Diagram of these 3 tables:
What I want is based on a patients amka(int) to find all his appointments and show his name, surname and doctors name, surname.
I made this query:
(SELECT doctor.name, doctor.surname
FROM public.doctor
INNER JOIN public.appointment ON doctor.username = 'alouisot2')
union
(SELECT patient.name, patient.surname
FROM public.patient
INNER JOIN public.appointment ON patient.amka = '713783001');
The problem with this query is that it will only show appointments between this specific doctor and I just want to get all the doctors names and surnames.
Also I use postgresql.
I was trying to figure it out but I couldn't. I need to restructure the query but I cannot think how I would solve this problem.
If you have any idea on how to do achieve this I would really appreciate it.
Try this - properly join the three tables together (doctor to appointment based on the common username column, appointment to patient on the common amka column), and define the WHERE clause with your desired values:
SELECT
doctor.name, doctor.surname,
patient.name, patient.surname
FROM
public.doctor
INNER JOIN
public.appointment ON doctor.username = appointment.username
INNER JOIN
public.patient ON appointment.amka = patient.amka
WHERE
doctor.username = 'alouisot2'
AND patient.amka = '713783001';
this query just needs simple joins; you seem to have overcomplicated it a lot for some reason...
SELECT
patient.name,
patient.surname,
doctor.name,
doctor.surname
FROM public.patient
INNER JOIN public.appointment
ON patient.amka = appointment.amka
INNER JOIN public.doctor
ON appointment.username = doctor.username
WHERE patient.amka = '713783001'
I have a database in Access. The database has 4 tables:
[DEPARTMENT], [TEACHER], [LECTURE], [SGROUP].
I need to display a list of departments whose teachers teach DBMS department students.
The question is: how to do it? I think it should be a query to join multiple times on the same table ... but I don't understand which table to join ...
I'm a noob.
First, you need to add DepNo value which 3, so the concatenation logically works
INNER JOIN displays everything you want about;
departments whose teachers teach DBMS department students
SELECT DEPARTMENT.DepNo, TEACHER.TechNo, TEACHER.name, DEPARTMENT.name, TEACHER.post
FROM DEPARTMENT
INNER JOIN TEACHER ON DEPARTMENT.DepNo=TEACHER.DepNo
ORDER BY TEACHER.name;
Image chart for What's the INNER JOIN:
Reference:
SQL Joins
Can anyone help me how to possibly do this query:
I have 2 tables namely Students and Subjects, and what I want to do is get all the students with more than one subjects in the Subject table. Also I want to show the count of subjects that each student has.
Thanks you!
use join between Students and Subjects tables ,and for count aggregate function , below query can be your solution
select st.id,st.name,count(sb.subjectid) as numberofTakenSubject
from Students st inner join Subjects sb
on st.id=sb.student_id
group by st.id,st.name
having count(*)>1
BTW your question should be more clear and specific like
Students and Subject tables structure and sample data
Try this:
select studentid,count(subjectid) from students inner join subjects
on student.id=subjects.studentid
group by studentid
having count(subjectid)>1
I have 2 tables, students and courses. In the students table each student has a course code and in the courses table I have course codes with their names.
How can I return the course name when running the query?
So for example if I run a basic SELECT * FROM Students it says "Jimmy | Computing" instead of "Jimmy | 12390814"
JOIN both tables. Try something like this,
SELECT a.*, b.courseName
FROM students a
INNER JOIN courses b
ON a.courseCode = b.courseCode
-- WHERE ....
I am having a few issues with a DB query.
I have two tables, students (Fields: FirstName, LastName, StdSSN), and teachers (TFirstName, TLastName, TSSN) which I've stripped down for this example. I need to perform a query that will return all the students except for the students that are teachers themselves.
I have the query
SELECT student.FirstName, student.LastName
FROM `student`,`teachers`
WHERE student.StdSSN=teachers.TSSN
Which gives me a list of all the teachers who are also students it does not provide me with a list of students who are not teachers, so I tried changing to:
SELECT student.FirstName, student.LastName
FROM `student`,`teachers`
WHERE student.StdSSN!=teachers.TSSN
Which gives me a list of all the students with many duplicate values so I am a little stuck here. How can I change things to return a list of all students who are not teachers? I was thinking INNER/OUTER/SELF-JOIN and was playing with that for a few hours but things became complicated and I did not accomplish anything so I've pretty much given up.
Can anyone give me any advice? I did see the query before and it was pretty simple, but I've failed somewhere.
Using NOT IN
SELECT s.*
FROM STUDENTS s
WHERE s.stdssn NOT IN (SELECT t.tssn
FROM TEACHERS t)
Using NOT EXISTS
SELECT s.*
FROM STUDENTS s
WHERE NOT EXISTS (SELECT NULL
FROM TEACHERS t
WHERE t.tssn = s.stdssn)
Using LEFT JOIN / IS NULL
SELECT s.*
FROM STUDENTS s
LEFT JOIN TEACHERS t ON t.tssn = s.stdssn
WHERE t.column IS NULL
I used "column" for any column in TEACHERS other than what is joined on.
Comparison:
If the column(s) compared are nullable (value can be NULL), NOT EXISTS is the best choice. Otherwise, LEFT JOIN/IS NULL is the best choice (for MySQL).