Write a big sql query or handle it through code? - mysql

Question

I have 2 tables built in this way:
Trips
- id
- organization_id REQUIRED
- collaboration_organization_id OPTIONAL
...other useless fields...
Organizations
- id
- name REQUIRED
...other useless fields...
Now I have been asked to create this type of report:
I want the sum of all trips for each organization, considering that if
they have a collaboration_organization_id it should count as 0.5,
obviusly the organization in collaboration_organization_id get a +0.5
too
So whenever I have a trip that has organization_id AND collaboration_organization_id set, that trip count as 0.5 for both organizations. If instead only organization_id is set, it counts as 1.
Now my question is composed by two parts:
1.
Is a good idea to "solve" the problem all in SQL?
I already know how to solve it through code, my idea is currently "select all trips (only those 3 fields) and start counting in ruby". Please consider that I'm using ruby on rails so could still be a good reason to say "no because it will work only on mysql".
2.
If point 1 is YES, I have no idea how to count for 0.5 each trip where it's required, because count is a "throw-in-and-do-it" function

Answer 1

I'm not familiar with ruby on rails, but this is how you can do this with MySQL.
Sample data:
CREATE TABLE Trips(
id int not null primary key,
organization_id int not null,
collaboration_organization_id int null
);
INSERT INTO Trips (id,organization_id,collaboration_organization_id)
VALUES
(1,1,5),
(2,1,1),
(3,1,2),
(4,11,1),
(5,1,null),
(6,2,null),
(7,10,null),
(8,6,2),
(9,1,3),
(10,1,4);
MySQL Query:
SELECT organization_id,
sum(CASE WHEN collaboration_organization_id IS null THEN 1 ELSE 0.5 End) AS number
FROM Trips
GROUP BY organization_id;
Try it out via: http://www.sqlfiddle.com/#!2/1b01d/107
EDIT: adding collaboration organization
Sample data:
CREATE TABLE Trips(
id int not null primary key,
organization_id int not null,
collaboration_organization_id int null
);
INSERT INTO Trips (id,organization_id,collaboration_organization_id)
VALUES
(1,1,5),
(2,1,1),
(3,1,2),
(4,11,1),
(5,1,null),
(6,2,null),
(7,10,null),
(8,6,2),
(9,1,3),
(10,1,4);
CREATE TABLE Organizations(
id int auto_increment primary key,
name varchar(30)
);
INSERT INTO Organizations (name)
VALUES
("Org1"),
("Org2"),
("Org3"),
("Org4"),
("Org5"),
("Org6"),
("Org7"),
("Org8"),
("Org9"),
("Org10"),
("Org11"),
("Org12"),
("Org13"),
("Org14"),
("Org15"),
("Org16");
MySQL query:
SELECT O.id, O.name,
sum(CASE WHEN T.collaboration_organization_id IS null THEN 1 ELSE 0.5 End) AS number
FROM Organizations AS O LEFT JOIN Trips AS T
ON T.organization_id = O.id OR T.collaboration_organization_id = O.id
WHERE T.collaboration_organization_id = O.id OR O.id = T.organization_id
GROUP BY O.id;
http://www.sqlfiddle.com/#!2/ee557/15