query SQL how to check all records from a three table join share the same value

Question

Hello

Since i'm a poor sql developer, i need support to write a sql query for the following scenario (just a simplified example of my situation):
i've got 3 tables, say employe table,department table and companybranch table. the dept column , on the employe table is a fk on the department table; the branch column on the department table is a fk on the companybranch table. Finally more employee are "marked" with the same value . There's a way to select all employes with the same "mark" and, in the same query, check that they work in the same company branch ?

thank you in advance

Stefano

Answer 1

Something like this would work:

SELECT * 
FROM employee e
JOIN department d ON e.dept = d.id
JOIN companybranch b ON d.branch = b.id
WHERE e.mark = 'mark here'
AND b.id = 'Branch id here'

EDIT

if you can't filter by branch, cause you don't know its value, then you can make a DISTINCT query, to check the differents b.id

SELECT DISTINCT b.id branch_id
FROM employee e
JOIN department d ON e.dept = d.id
JOIN companybranch b ON d.branch = b.id
WHERE e.mark = 'mark here'

this is another option, you can check

SELECT inside.branch_id, COUNT(*) total
FROM (
    SELECT b.id branch_id
    FROM employee e
    JOIN department d ON e.dept = d.id
    JOIN companybranch b ON d.branch = b.id
    WHERE e.mark = 'mark here'
    ) inside
GROUP BY inside.branch_id