Inner join with multiple tables - sql

Question

I have these four tables:
PRODUCTS
---------
PRODUCT_ID
PRODUCT_TITLE
(other fields)
COLORS
---------
COLOR_ID
COLOR_NAME
MATERIALS
---------
MATERIAL_ID
MATERIAL_NAME
IMAGES
---------
IMAGE_ID
BIG
MED
SMALL
THUMB
SIZE
---------
SIZE_ID
SIZE_NAME
And also:
PRODUCT_COLOR
---------
PRODUCT_ID
COLOR_ID
PRODUCT_MATERIAL
---------
PRODUCT_ID
MATERIAL_ID
PRODUCT_SIZE
---------
PRODUCT_ID
SIZE_ID
PRODUCT_IMAGE
---------
PRODUCT_ID
IMAGE_ID
COLOR_ID (can be null)
MATERIAL_ID (can be null)
All the products can have a different color and/or material. E.g. I can have a product that has one or more material options but no colors associated and vice versa. The output should be something like this:
-----------------------------------------------------------------------------
| PRODUCT_ID | PRODUCT_NAME | COLOR_ID | MATERIAL_ID | IMAGE_ID | SIZE_ID |
-----------------------------------------------------------------------------
| 1 | T-SHIRT | 1 | null | 1 | 1 |
| 1 | T-SHIRT | 1 | null | 1 | 2 |
| 1 | T-SHIRT | 1 | null | 1 | 3 |
| 1 | T-SHIRT | 1 | null | 1 | 4 |
| 2 | JEANS | null | 1 | 2 | 1 |
| 2 | JEANS | null | 1 | 2 | 2 |
| 2 | JEANS | null | 1 | 2 | 3 |
| 2 | JEANS | null | 1 | 2 | 4 |
| 2 | JEANS | null | 1 | 2 | 5 |
| 3 | T-SHIRT VNECK | 2 | 2 | 3 | 1 |
| 3 | T-SHIRT VNECK | 2 | 2 | 3 | 2 |
| 3 | T-SHIRT VNECK | 3 | 2 | 4 | 1 |
| 3 | T-SHIRT VNECK | 3 | 2 | 4 | 2 |
| 3 | T-SHIRT VNECK | 4 | 3 | 5 | 1 |
| 3 | T-SHIRT VNECK | 4 | 3 | 5 | 2 |
-----------------------------------------------------------------------------
I have tried the following statement but it returns 0 rows:
SELECT PRODUCTS.PRODUCT_ID, PRODUCTS.PRODUCT_TITLE, COLORS.COLOR_ID, MATERIALS.MATERIAL_ID, IMAGES.IMAGE_ID, SIZE.SIZE_ID from PRODUCTS
INNER JOIN PRODUCT_COLOR ON (PRODUCTS.PRODUCT_ID = PRODUCT_COLOR.PRODUCT_ID)
INNER JOIN COLORS ON (COLORS.COLOR_ID = PRODUCT_COLOR.COLOR_ID)
INNER JOIN PRODUCT_MATERIAL ON (PRODUCTS.PRODUCT_ID = PRODUCT_MATERIAL.PRODUCT_ID)
INNER JOIN MATERIALS ON (MATERIALS.MATERIAL_ID = PRODUCT_MATERIAL.MATERIAL_ID)
INNER JOIN PRODUCT_IMAGE ON (PRODUCTS.PRODUCT_ID = PRODUCT_IMAGE.PRODUCT_ID)
INNER JOIN IMAGES ON (IMAGES.IMAGE_ID = PRODUCT_IMAGE.IMAGE_ID)
INNER JOIN PRODUCT_SIZE ON (PRODUCTS.PRODUCT_ID = PRODUCT_SIZE.PRODUCT_ID)
INNER JOIN SIZE ON (SIZE.SIZE_ID = PRODUCT_SIZE.SIZE_ID)
ORDER BY PRODUCTS.id_PRODUCT;
Any ideas?

Answer 1

You could do something like this:
select p.product_id,
p.product_name,
c.color_id,
m.material_id,
i.image_id,
s.size_id
from products p
left join product_color pc
on p.product_id = pc.product_id
left join colors c
on pc.color_id = c.colorid
left join product_material pm
on p.product_id = pm.product_id
left join materials m
on pm.material_id = m.material_id
left join product_image pi
on p.product_id = pi.product_id
left join images i
on pi.image_id = i.image_id
or c.color_id = i.color_id
or m.material_id = i.material_id
left join product_size ps
on p.product_id = ps.product_id
left join size s
on ps.size_id = s.size_id
I would advise you reviewing JOINs. There is a great visual explanation of joins online that will help you write these queries.

Answer 2

Well, you need to learn how to build joins, and the way I normally do it is by selecting one table and join the next one and the next one and the next one until I have the result I want.
select product_id, product_name
from products
next I join the first one I need so I go ahead and say
select p.product_id, p.product_name, pc.color_id
from products p
join product_color pc on (pc.product_id = p.product_id)
On the join it is important to figure out if I maybe have nothing to join with and I still want to see the line. So I rather use a left join
select p.product_id, p.product_name, pc.color_id
from products p
left join product_color pc on (pc.product_id = p.product_id)
That way you add each table to join. By the way. Is this homework?

Answer 3

If you just need IDs, keep it simple
select p.product_id,
p.product_name,
pc.color_id,
pm.material_id,
pi.image_id,
ps.size_id
from products p,
PRODUCT_COLOR pc,
product_material pm,
PRODUCT_SIZE ps,
PRODUCT_IMAGE pi
where
p.product_id = pc.product_id(+)
and p.product_id = pm.product_id(+)
and p.product_id = ps.product_id(+)
and p.product_id = pi.product_id(+);