MySQL getting duplicates using multiple left join

For some reason I'm getting duplicate values from the Tags and Person table using following query:

# Selects
SELECT 
Organization.name AS 'Name',
GROUP_CONCAT(Person.name) AS 'Persons',
GROUP_CONCAT(Tag.name) AS 'Tags'

# From
FROM Organization

# Joins
LEFT JOIN Person ON Organization.id = Person.organizationID
LEFT JOIN Refs ON Organization.id = Refs.fromID
LEFT JOIN Tag ON Tag.id = Refs.toID

GROUP BY Organization.id

If I remove the "Person" or "Refs + Tag" JOIN, duplicates dissappear. I'm a bit confused with this problem.

Here is a link for the SQL Fiddle: http://sqlfiddle.com/#!9/6251f/3/0

Solution

The join to the tags/refs tables is causing each organization, and therefore the people inside that organization, to be duplicated. You may try aggregating both persons and tags in separate subqueries. The following seems to work:

SELECT 
    org.name AS Name,
    t1.Persons,
    t2.Tags
FROM Organization org
LEFT JOIN
(
    SELECT organizationID, GROUP_CONCAT(name) AS Persons
    FROM Person
    GROUP BY organizationID
) t1
    ON org.id = t1.organizationID
LEFT JOIN
(
    SELECT r.fromID, GROUP_CONCAT(t.name) AS Tags
    FROM Refs r
    LEFT JOIN Tag t
        ON t.id = r.toID
    GROUP BY r.fromID
) t2
    ON org.id = t2.fromID;

MySQL getting duplicates using multiple left join

Demo