MySQL query to get the total from three tables - mysql

Question

Using MySQL, how do I get the total items and total revenue for each manager's team? Suppose I have these 3 different tables (parent-child-grandchild):
Employee1 is under Supervisor1, and they are both under Manager1, and so on, but real data are in random arrangement. Color-coded the numbers to visualize which gets added.
I want my query to output the total items and total revenue of each manager's team like:
To easily create the table:
DROP TABLE IF EXISTS manager;
CREATE TABLE manager (id int, name varchar(55), no_of_items int, revenue int);
INSERT INTO manager (id, name, no_of_items, revenue)
VALUES
(1 , 'Manager1' , 10 , 100),
(2 , 'Manager2' , 20 , 200),
(3 , 'Manager3' , 30 , 300);
DROP TABLE IF EXISTS supervisor;
CREATE TABLE supervisor (id int, name varchar(55), manager_id int, no_of_items int, revenue int);
INSERT INTO supervisor (id, name, manager_id, no_of_items, revenue)
VALUES
(4 , 'Sup1' , 1, 100 , 1000),
(5 , 'Sup2' , 2, 200 , 2000),
(6 , 'Sup3' , 3, 300 , 3000);
DROP TABLE IF EXISTS employee;
CREATE TABLE employee (id int, name varchar(55), supervisor_id int, no_of_items int, revenue int);
INSERT INTO employee (id, name, supervisor_id, no_of_items, revenue)
VALUES
(7 , 'Emp1' , 4, 400 , 4000),
(8 , 'Emp2' , 5, 500 , 5000),
(9 , 'Emp3' , 4, 600 , 6000);

Answer 1

SQL Fiddle
Utilizing a combination of Nested Subqueries and UNION ALL, you can use the following:
SELECT inner_nest.manager_id,
inner_nest.name,
SUM(inner_nest.total_items) AS total_items,
SUM(inner_nest.total_revenue) AS total_revenue
FROM (
SELECT id as manager_id,
name,
SUM(no_of_items) AS total_items,
SUM(revenue) AS total_revenue
FROM manager
GROUP BY id
UNION ALL
SELECT m.id as manager_id,
m.name,
SUM(s.no_of_items) AS total_items,
SUM(s.revenue) AS total_revenue
FROM manager m
INNER JOIN supervisor s ON s.manager_id = m.id
GROUP BY m.id
UNION ALL
SELECT m.id as manager_id,
m.name,
SUM(e.no_of_items) AS total_items,
SUM(e.revenue) AS total_revenue
FROM manager m
INNER JOIN supervisor s ON s.manager_id = m.id
INNER JOIN employee e ON e.supervisor_id = s.id
GROUP BY m.id
) AS inner_nest
GROUP BY inner_nest.manager_id

Answer 2

Try this: http://sqlfiddle.com/#!9/7a0aef/20
select id,name,COALESCE(sum(distinct m),0)+COALESCE(sum(distinct s),0)+COALESCE(sum(e),0)
as total_item,COALESCE(sum(distinct mv),0)+COALESCE(sum(distinct sv),0)+COALESCE(sum(ev),0)
as total_revenue
from
(
select m.id,m.name,m.no_of_items as m,s.no_of_items as s,e.no_of_items as e,
m.revenue as mv,s.revenue as sv,e.revenue as ev
from manager m left join supervisor s
on m.id=s.manager_id
left join employee e on s.id=e.supervisor_id)a
group by id,name

Answer 3

A single query with the appropriate joins does the trick... In pseudo code (sorry, I'm typing on my phone)
Select a.manager_id, (a.total_items+b.total_items+c.total_items) as totalitems, (a.total_revenue+b.total_revenue+c.total_revenue) as totalrevenue
From parent_table a
Join child_table b on a.manager_id=b.manager.id
Join grandchild_table c on b.sup_id=c.sup_id
Group by a.manager_id
Some adjustments may be needed, but this should definitely point you in your way