Populate/Join multiple tables of many to many relationship table in mysql - mysql

Question

This question should have been asked before, but I am finding it hard to find.
I have table users,allergies,dietaries. users can have multiple allergies,and multiple dietaries. So for that I have user_allergies, user_dietaries table which store both tables foreign key.
Now I want to show list of users with their corresponding allergies, dietaries name. I tried with left join like this -->
SELECT
users.user_id as 'id',
IFNULL(CONCAT(users.first_name,' ',users.last_name),'') as 'name',
IFNULL(GROUP_CONCAT(allergies.title),'') as 'allergies'
FROM (users
LEFT JOIN user_allergies
ON users.user_id = user_allergies.user_id
LEFT JOIN allergies
ON user_allergies.allergies_id = allergies.allergies_id
)
GROUP BY users.user_id;
Which respond exactly like I want-->
7 | Khabib Nurmagamedov | Milk,Corn
8 | Conor Mcgregor | Milk,Corn
Now I wish to get the dietaries same way. So I added Left Join for dietaries similarly -->
SELECT
users.user_id as 'id',
IFNULL(CONCAT(users.first_name,' ',users.last_name),'') as 'name',
IFNULL(GROUP_CONCAT(allergies.title),'') as 'allergies',
IFNULL(GROUP_CONCAT(dietaries.title),'') as 'dietaries'
FROM (users
LEFT JOIN user_allergies
ON users.user_id = user_allergies.user_id
LEFT JOIN allergies
ON user_allergies.allergies_id = allergies.allergies_id
LEFT JOIN user_dietaries
ON users.user_id = user_dietaries.user_id
LEFT JOIN dietaries
ON user_allergies.allergies_id = dietaries.dietaries_id
)
GROUP BY users.user_id;
But now the output I get -->
7 | Khabib Nurmagamedov | Milk,Corn,Eggs,Meat | Milk,Corn,Eggs,Meat
8 | Conor Mcgregor | Milk,Corn,Eggs,Meat | Milk,Corn,Eggs,Meat
Which should be -->
7 | Khabib Nurmagamedov | Milk,Corn | Eggs,Meat
8 | Conor Mcgregor | Milk,Corn | Eggs,Meat
I am struggling here. What should I do?
Thanks In Advance.
Edit:
Te response is -->
7 | Khabib Nurmagamedov | Milk,Corn,Milk,Corn | Milk,Milk,Corn,Corn
8 | Conor Mcgregor | Milk,Eggs,Milk,Eggs | Milk,Milk,Corn,Corn
I thought both table data getting concatenated but apparently result is appearing twice.
Result needs to be-->
7 | Khabib Nurmagamedov | Milk,Corn | Milk,Corn
8 | Conor Mcgregor | Milk,Eggs | Milk,Corn

Answer 1

Your issue is that you want your GROUP_CONCAT in 2 separate columns, and it can't work like that.
You have to join your group_concat results 2 times, from the user table:
SELECT u.user_id as 'id',
IFNULL(CONCAT(u.first_name,' ',u.last_name),'') as 'name',
ua.allergies_c as 'allergies',
ud.dietaries_c as 'dietaries'
FROM users u
LEFT JOIN
(
SELECT
users.user_id ,
IFNULL(GROUP_CONCAT(allergies.title),'') as allergies_c
FROM (users
LEFT JOIN user_allergies
ON users.user_id = user_allergies.user_id
LEFT JOIN allergies
ON user_allergies.allergies_id = allergies.allergies_id
)
GROUP BY users.user_id
) ua ON u.user_id=ua.user_id
LEFT JOIN
(
SELECT
users.user_id,
IFNULL(GROUP_CONCAT(dietaries.title),'') as dietaries_c
FROM (users
LEFT JOIN user_dietaries
ON users.user_id = user_dietaries.user_id
LEFT JOIN dietaries
ON user_dietaries.dietaries_id = dietaries.dietaries_id
)
GROUP BY users.user_id
) ud ON u.user_id=ud.user_id
I made some mass-replace to go faster, you might have a few things to fix, but the idea is there.

Answer 2

By adding Distinct before allergies.title and dietaries.title, I can get my desired result.
But not sure why title fields were appearing twice.
SELECT
users.user_id as 'id',
IFNULL(CONCAT(users.first_name,' ',users.last_name),'') as 'name',
IFNULL(GROUP_CONCAT(Distinct allergies.title),'') as 'allergies',
IFNULL(GROUP_CONCAT(Distinct dietaries.title),'') as 'dietaries'
FROM (users
LEFT JOIN user_allergies
ON users.user_id = user_allergies.user_id
LEFT JOIN allergies
ON user_allergies.allergies_id = allergies.allergies_id
LEFT JOIN user_dietaries
ON users.user_id = user_dietaries.user_id
LEFT JOIN dietaries
ON user_allergies.allergies_id = dietaries.dietaries_id
)
GROUP BY users.user_id;