SQL to generate report of entity-attribute-value structured data - sql

Question

I have 3 tables:
Productmaster:
ProductId PName PDescription
Attributes:
AttributeID attName
---- ----
1 Brand
2 Category
3 Artist
ProductAttributeValues
paId ProductId AttributeID AttributeValues
A product can have multiple attributes.
Here's the desired output:
ProductId ProductDesc Brand Category Artist
--- --- --- --- ---
1 sadasd Brand1 Category1 Artist1
2 sadasds Brand2 Category3 Artist4
How can I get this output?
Thanks in advance.

Answer 1

You should left join for each attribute value you want to pull in, e.g.
select p.ProductId,p.ProductDesc,
a1.AttributeValues as Brand,
a2.AttributeValues as Category,
a3.AttributeValues as Artist,
from Product p
left join ProductAttributeValues a1 on(p.ProductId=a1.ProductId and a1.AttributeID=1)
left join ProductAttributeValues a2 on(p.ProductId=a2.ProductId and a2.AttributeID=2)
left join ProductAttributeValues a3 on(p.ProductId=a3.ProductId and a3.AttributeID=3)
To turn this back into English, "give me all products, and for each one, give me a brand, category and artist attribute if they exist"
I've assumed that a product has only one or zero values for each attribute.

Answer 2

Assumed that every attribute appears exactly once per product:
SELECT
pm.ProductId as ProductId,
pm.PDescription as ProductDesc,
pav_Brand.AttributeValues as Brand,
pav_Category.AttributeValues as Category,
pav_Artist.AttributeValues as Artist
FROM
ProductMaster pm
inner join ProductAttributeValues pav_Brand
on pm.productId == pav_Brand.ProductId
inner join Attributes a_Brand
on pav_Brand.AttributeId = a_Brand.AttributeId
AND a_Brand.attName = 'Brand'
inner join ProductAttributeValues pav_Category
on pm.productId == pav_Category.ProductId
inner join Attributes a_Category
on pav_Category.AttributeId = a_Category.AttributeId
AND a_Brand.attName = 'Category'
inner join ProductAttributeValues pav_Artist
on pm.productId == pav_Artist.ProductId
inner join Attributes a_Artist
on pav_Category.AttributeId = a_Artist.AttributeId
AND a_Brand.attName = 'Artist'
You can use left outer joins if the data is not always available.

Answer 3

SELECT ProductId, ProductDesc,
(
SELECT AttributeValues
FROM ProductAttributeValues pv
WHERE pv.AttributeID = 1
AND pv.ProductID = p.ProductID
) AS Brand,
(
SELECT AttributeValues
FROM ProductAttributeValues pv
WHERE pv.AttributeID = 2
AND pv.ProductID = p.ProductID
) AS Category,
(
SELECT AttributeValues
FROM ProductAttributeValues pv
WHERE pv.AttributeID = 3
AND pv.ProductID = p.ProductID
) AS Artist
FROM Products p

Answer 4

Try this query, maybe some tweak required
Select pm.ProductId, pm.PDescription, pav1.AttributeValues, pav2.AttributeValues, pav3.AttributeValues
from Productmaster pm, ProductAttributeValues pav1, ProductAttributeValues pav2, ProductAttributeValues pav3
where pm.ProductId = pav1.ProductId
and pav1.AttributeID = 1
and pm.ProductId = pav2.ProductId
and pav2.AttributeID = 2
and pm.ProductId = pav3.ProductId
and pav3.AttributeID = 3