joint three tables in Mysql - mysql

Question

I have three tables employee, promotion and punishment
Employee’s table structure something like this
Id int
Fullname varchar
...............
promotionDate date
Promotion’s table structure is like this
id int
emp_id int
directorateDate date
And punishment’s table structure is like this
id int
emp_id int
direcotorateDate date
Let’s say employee table has 200 records, each month a group of employees have promotion (after serving one year), I want to get the list of all employees in the current month that get promotion
I can easily get the list by this query
SELECT *
FROM employee
WHERE MONTH(promotionDate) = MONTH(CURRENT_DATE())
AND YEAR(promotionDate) = YEAR(CURRENT_DATE())
My question is
I want to count number of punishments and promotions each employee got in the current year from punishment and promotion table respectively
I did this query but it did not get right results
SELECT e.fullname , COUNT(punish.emp_id) as siza ,COUNT(pro.emp_id) as supas
FROM emp_employee as e
LEFT JOIN emp_punishment as punish on punish.emp_id=e.id
LEFT JOIN emp_promotion as pro on e.id=pro.emp_id
WHERE ((MONTH(e.promotionDate) = MONTH(CURRENT_DATE())
AND YEAR(e.promotionDate) = YEAR(CURRENT_DATE()))
AND ( YEAR(punish.directorate_date) = YEAR(CURRENT_DATE()) )
AND ( YEAR(pro.directorate_date) = YEAR(CURRENT_DATE()) )
GROUP BY e.fullname;
Any help please.

Answer 1

By joining directly the 3 tables you get duplicate rows.
Group by emp_id and aggregate separately each of the tables emp_punishment and emp_promotion and join the results to the table emp_employee.
select e.fullname, coalesce(pu.siza, 0) siza, coalesce(pr.supas, 0) supas
from emp_employee as e
left join (
select emp_id, count(*) siza
from emp_punishment
where year(directorate_date) = year(CURRENT_DATE)
group by emp_id
) pu on pu.emp_id = e.id
left join (
select emp_id, count(*) supas
from emp_promotion
where year(directorate_date) = year(CURRENT_DATE)
group by emp_id
) pr on pr.emp_id = e.id
I used only the condition:
where year(directorate_date) = year(CURRENT_DATE())
because in your question you say:
I want to count number of punishments and promotions each employee got in the current year from punishment and promotion

Answer 2

Removing MONTH() function, and moving each condition to their respective place, instead of within the WHERE clause should resolve the issue (Since, they're considered as if INNER JOINs with the current style ).
Only keep common column e.promotionDate within the WHERE clause :
SELECT e.fullname,
COUNT(punish.emp_id) as siza ,
COUNT(pro.emp_id) as supas
FROM emp_employee as e
LEFT JOIN emp_punishment as punish
ON punish.emp_id=e.id
AND YEAR(punish.directorate_date) = YEAR(CURRENT_DATE())
LEFT JOIN emp_promotion as pro
ON e.id=pro.emp_id
AND YEAR(pro.directorate_date) = YEAR(CURRENT_DATE()))
WHERE YEAR(e.promotionDate) = YEAR(CURRENT_DATE())
GROUP BY e.fullname;