I need to calculate the average production per employee per month

Question

I need to create a report showing the employees that produced on average at least 30 pieces/ day

I have 2 tables:

Employees: id, name, surname
Production: id, date_time, id_employee, [..], quantity_produced

the id from the employees table = id_employee from the production table

---

SELECT name, surname, Avg(quantity_produced), Month(data_ora) Mnth
FROM production inner join employees on employees.id = production.id_employee
GROUP BY name, quantity_produced, Month(date_time);

OR

select name, surname, quantity_produced, avg(quantity_produced) as avgentrypermonth 
    from (
select month(date_time) as month ,count(1) as quantity
     group by month(date_time));

OR

select name, surname, quantity_produced
    from production 
     inner join employees on employees.id = production.id_employee
    where avg(quantity_produced) > 30;

Answer 1

I would most likely go for one off the queries below.

But hard to suggest something solid without example data and expected results.

Query:

SELECT 
    Production.id_employee,
    AVG(Production.quantity_produced)
FROM 
    Production
WHERE
    Production.date_time BETWEEN
                         (LAST_DAY(NOW()) + INTERVAL 1 DAY) - INTERVAL 1 MONTH # first day of current month
                         AND
                         LAST_DAY(NOW()) # last day of current month
GROUP BY 
    Production.id_employee

Query when you need the employees record instead:

SELECT 
    Employees.name,
    Employees.surname,
    AVG(Production.quantity_produced)
FROM 
    Production
INNER JOIN 
    Employees ON Production.id_employee = Employees.id
WHERE
    Production.date_time BETWEEN
                         (LAST_DAY(NOW()) + INTERVAL 1 DAY) - INTERVAL 1 MONTH  # first day of current month
                         AND
                         LAST_DAY(NOW()) # last day of current month
GROUP BY 
    Employees.id

Note the query above assumes at least MySQL 5.7.5+ and SQL 1999+ standards optional feature which is called functional dependency .

See manual

Or as co-related subqueries: which should be fine when indexed correctly

SELECT 
    (SELECT Employees.name FROM Employees.id = Production.id_employee) AS name,
    (SELECT Employees.surname FROM Employees.id = Production.id_employee) AS surname,
    AVG(Production.quantity_produced)
FROM 
    Production
WHERE
    Production.date_time BETWEEN
                         (LAST_DAY(NOW()) + INTERVAL 1 DAY) - INTERVAL 1 MONTH # first day of current month
                         AND LAST_DAY(NOW()) # last day of current month
GROUP BY 
    Production.id_employee

Answer 2

for filter aggregated result you need having clause

SELECT name, surname, Avg(quantity_produced), Month(date_time) Mnth
FROM production 
inner join employees on employees.id = production.id_employee
GROUP BY name, surname, Month(date_time)
having Avg(quantity_produced) > 30 ;

and with year too

SELECT name, surname, Avg(quantity_produced), Month(date_time) Mnth, year(date_time) year
FROM production 
inner join employees on employees.id = production.id_employee
GROUP BY name, surname, Month(date_time), year(date_time) year
having Avg(quantity_produced) > 30 ;

Answer 3

When working with months, you should be sure that you are taking the year into account as well:

SELECT year(p.data_ora) as yyyy, month(p.data_ora) as mm,
       e.name, e.surname, avg(p.quantity_produced),
FROM production p inner join
     employees e
     on e.id = p.id_employee
GROUP BY year(p.data_ora), month(p.data_ora,
         e.name, e.surname
HAVING avg(p.quantity_produced) >= 30
ORDER BY year(p.data_ora), month(p.data_ora),
         e.name, e.surname;

This assumes that production has the quantity produced per day that the employee works.

Notes:

• Qualify all column references when your table references more than one table.
• Use table aliases so the query is easier to write and to read.
• Remember the year! (when you are working with months)

Answer 4

    I think this should work , can you please try it once. And may be little modification required, Comment here I will try to do the fixes.
  1.Select
         E.id "Employee ID",
         E.name "Employee Name",
         Month(P.date_time) "Month",
         AVG(P.quantity_produced) "Quantity Produced"
    From Employee as E
         Join Production as P on E.id=P. id_employee
    Group by
         E.id,E.name,Month(P.date_time)
    Having Avg(P.quantity_produced) > 30

2.Select
         E.name "Employee Name",
         Month(P.date_time) "Month",
         AVG(P.quantity_produced) "Quantity Produced"
    From Employee as E
         Join Production as P on E.id=P. id_employee
    Group by
         E.name,Month(P.date_time)
    Having Avg(P.quantity_produced) > 30