Why is my group by not grouping my values as expected? - sql

Question

My project is a clothes factory and I have 3 tables.
Person : A table that contains people's name
Category : Contains each category of clothes in the factory (sockets, shoes, etc.)
Quantity : The quantity of clothes for each person
SELECT Name,
sum(case when category = 'shoes' then quantity else 0 end) as 'Quantity_shoes',
sum(case when category = 'shirts' then quantity else 0 end) as 'Quantity_shirts',
sum(case when category = 'sockets' then quantity else 0 end) as 'Quantity_shirts',
sum(case when category = 'hats' then quantity else 0 end) as 'Quantity_hats'
FROM person p
join inventory i
on i.person_id = p.id
join category c
c.id = i.category_id
WHERE p = 'Paul'
GROUP BY name,
category
And I'm trying to display something like this :
Name
Quantity_shoes
Quantity_shirts
Quantity_sockets
Quantity_hats
Paul
8
25
38
0
But my result isn't that I expected... I got this :
Name
Quantity_shoes
Quantity_shirts
Quantity_sockets
Quantity_hats
Paul
8
0
0
0
Paul
0
0
0
0
Paul
0
25
0
0
Paul
0
0
38
0
It seems that I have one row for each category. So I tried to groupbyquantity but it doesn't sum my quantity and I have more rows.
What I am doing wrong?

Answer 1

As suggested in the above try this (I am guessing the column in person with the name is p.name in which case you may not even need the group by name):
SELECT
Name,
sum(case when category = 'shoes' then quantity else 0 end) as 'Quantity_shoes',
sum(case when category = 'shirts' then quantity else 0 end) as 'Quantity_shirts',
sum(case when category = 'sockets' then quantity else 0 end) as 'Quantity_shirts',
sum(case when category = 'hats' then quantity else 0 end) as 'Quantity_hats'
FROM
person p
join inventory i on i.person_id = p.id
join category c.id = i.category_id
WHERE
p.name = 'Paul'