I have a table of students:
id | age
--------
0 | 25
1 | 25
2 | 23
I want to query for all students, and an additional column that counts how many students are of the same age:
id | age | count
----------------
0 | 25 | 2
1 | 25 | 2
2 | 23 | 1
sql querry should look like :
SELECT age, count(age)
FROM Students
GROUP by age
If you need the id as well you could include the above as a sub query like so:
SELECT S.id, S.age, C.cnt
FROM Students S
INNER JOIN (SELECT age, count(age) as cnt
FROM Students
GROUP BY age) C ON S.age = C.age
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