Students Table:
ID | Family_ID | Student_name | F_name
Families Table:
ID | F_name | Contact_No
i want to get all records from students where family_id is repeating.(basically i want to know students Brothers/Sisters records if there is any in student table.
i tried it this way but got wrong output;
SELECT students.*
FROM students
INNER JOIN families
ON families.id = students.family_id
ORDER BY families.id ASC
my query result in image: as you can see some ids are showing once others are more then once, but i think all should appear more then once.
If you want to see only relevant people you don't need to link it to the families table. You can group the student with family_id. Here is your query :
SELECT *
FROM Student
WHERE family_id IN (SELECT family_id
FROM students
GROUP BY family_id
HAVING COUNT(1)>1)
ORDER BY family_id
You could try using a join on subquery for the family_id that have more that one rows in students
SELECT students.*
FROM students
inner join (
select students.family_id
FROM students
group by students.family_id
having count(*)>1
) t on t. family_id = students.family_id
Related
As I'm SQL beginner, I can't describe a problem in a simple way, so let me show you an example:
3 Tables:
PRODUCT
id
group_id
person_id
GROUP
id
name
PERSON
id
group_id
As you see, GROUP can have multiple PERSONs and PRODUCT can be connected with GROUP and PERSON.
From this point, I would like to count number of PERSONs having a PRODUCT within a GROUP
I don't really understand the background of IN or using another SELECT within FROM, so if that's the point, then I'm happy that I was one step before it lol.
SELECT
group.name as GROUP_name,
COUNT(DISTINCT person_id) AS PERSON_having_min_one_PRODUCT
FROM products
LEFT JOIN groups ON groups.id = products.group_id
LEFT JOIN persons ON persons.id = products.person_id;
With this data:
GROUP
ExampleGroupName1 has 3 PERSONs, but 2 of them has >0 PRODUCTS
ExampleGroupName2 has 3 PERSONs and all of them has >0 PRODUCTS
ExampleGroupName3 has 2 PERSONs, but none of them has the PRODUCT
ExampleGroupName4 has 2 PERSONs, but only 1 has >0 PRODUCT
I would like to have an output like this:
GROUP_name | PERSON_having_min_one_PRODUCT
ExampleGroupName1 | 2
ExampleGroupName2 | 3
ExampleGroupName4 | 1
I would like to count number of PERSONs having a PRODUCT within a GROUP
Note: I will assume the table product does not have the column group_id, since it is redundant and can lead to a lot of errors.
The following query will show you the result you want by joining the tables person and product:
select
count(distinct x.id)
from person x
join product p on p.person_id = x.id
where x.group_id = 123 -- choosing a specific group
and p.id = 456 -- choosing a specific product
This would rather be simple like below meaning all the groups with some group_id with count(persons) and those count who has some product via id used in having clause
Select group_id,
count( distinct id ) AS "PERSON_WITH_PRODUCT"
from
person group by group_id having id
in (Select id from product);
I got 3 tables:
student
internship
student_internship
create table student(student_id varchar(45), student_name varchar(45));
create table internship(internship_id varchar(45), internship_name varchar(45));
and student_intership is the 'bridge' of the two tables.
student_intership(student_id, internship_id)
So, it is a many to many situation.
Situation:
I want to get the name of the internship and number of student, but
if there's no student for that internship, so it should have the following example:
intership_name | count(student_id)
--------------------------------
1. intern1 | 20
2. intern2 | 3
3. intern3 | 0
the code i have tried:
select internship.internship_id, count(student.student_id)
from student_internship, internship, student
where student_internship.student_id = student.student_id
and student_internship.internship_id = internship.internship_id
group by student_internship.internship_id;
Try this:
SELECT i.internship_name, COALESCE(COUNT(si.student_id), 0) AS cnt
FROM internship i
LEFT JOIN student_intership si ON i.internship_id = si.internship_id
GROUP BY si.internship_id, i.internship_name
The above query will return all records of table internship. It will return 0 for internship records having no relation to student records.
Quick stab:
SELECT st.student_id
,st.student_name
,si.InternshipCount
FROM student st
LEFT JOIN (
SELECT count(*) AS InternshipCount
,student_id
FROM student_internship s
INNER JOIN internship i
ON s.student_id = i.student_id
group by student_id
) AS si
ON st.student_id = si.student_id
I am using MySQL and database server and I have two tables one is for customer and another for customer_contacts.
Here are the table structures:
customer(
id(pk, ai)
name
email
)
and
customer_contacts(
id(ai)
customer_id
first_name
last_name
)
Now my question is:
lets say I have one customer has many customer_contacts like this
customer
id name email
1 john john#example.com
and customer_contacts is like this (first row)
id customer_id first_name last_name
1 1 john doe
2 1 johnp pual
like this
So here I want to get all the contact details count for the id john. So can some one tell me how to get that?
Any help and suggestions will be really appreciable. Thanks
If the id is already known (as suggested by the question, it would be a plain
SELECT COUNT(*) from customer_contacts
WHERE customer_contacts.id = 1;
You just need to know the number of contactacs for the customer John, right?
SELECT COUNT(*)
FROM customer cus INNER JOIN customer_contacts con ON cus.id = con.customer_id
WHERE cus.name = 'john'
Nevertheless, It would be better if you know the id of John. Your query would be this:
SELECT COUNT(*)
FROM customer_contacts
WHERE customer_id = 1
Simply join both tables and use count() with group by c.id use where to filter records
select c.*,
count(*) total_contacts
from customer c
left join customer_contacts cc on(c.id = cc.customer_id)
group by c.id
Fiddle Demo
I have 2 tables in a database person and order tables.
PERSON table:
PERSON_ID | NAME
ORDER table:
ORDER_ID | ORDER_NO | PERSON_ID
I need to display all the orders + a name of corresponding person if it exists, if not just order details.
So far I got up to query:
SELECT ORDER_ID, ORDER_NO, order.PERSON_ID, NAME
FROM person, order
WHERE person.PERSON_ID = order.PERSON_ID AND
person.FIRST_NAME IS NOT NULL;
Which gives me orders only if the name is available whereas I need to display all the orders despite the fact if name is available or not.
Any suggestions?
Yes, you can use LEFT JOIN for that:
SELECT o.order_id, o.order_no, o.person_id, p.name
FROM `order` o
LEFT JOIN person p
ON p.person_id = o.person_id AND p.FIRST_NAME IS NOT NULL
With LEFT JOIN if the name is null it will still give you the orders.
I need some help to create my select correctly...
Here is my tables :
**teacher** :
id
name
**classroom** :
id
teacher_id
**students** :
id
name
classroom_id
status
I am trying to select all the teachers that have a classroom.
Classroom may be selected only if ALL students have a status > 10...
If a student has a status 5 for example the classroom may NOT be selected and therefore the teacher may NOT be selected (besides he has a another OK classroom)
try this :
select * from teacher t
inner join classroom c on t.id=c.teacher_id
inner join
(select * from students
group by classroom_id having classroom_id not in
(select distinct classroom_id from students where status<=10)) s
on s.classroom_id=c.id
updated :
from your comment i think query above should work but you can test this query :
select * from teacher t where id in
(select distinct teacher_id from classroom where id in
(select distinct classroom_id from students
group by classroom_id having classroom_id not in
(select distinct classroom_id from students where status<=10)
)
)