Question

I have the following database structure:

`Products`
-------------------------------------
ID | ProductNo
-------------------------------------
1 | 3340
2 | 3450


`ProductVariants`
-------------------------------------
ID | MasterID (ref to `Products`.`ID`) | ProductNo
-------------------------------------
1 | 1 | 3341
2 | 1 | 3342
3 | 2 | 3451

How do I get the Products and their Product Variants with one query?

EDIT:

Desired result:

MasterID | IsMaster | ProductNo | VariantProductNo
1 | 1 | 3340 | null
1 | 0 | 3340 | 3341
1 | 0 | 3340 | 3342
2 | 1 | 3450 | null
2 | 0 | 3450 | 3451

Answer 1

This would do it

SELECT *
FROM Products
INNER JOIN ProductVariants
ON Products.ID = ProductVariants.MasterID

Normally done with a single query for efficiency (you could have a query on the Products table, loop round the results of that and for each one do a query on the ProductVariants table, but it would be dog slow).

You could use a LEFT OUTER JOIN instead if you wanted products for which there were no variants

To go with your updated requirements, something like this (not tested so excuse any typos)

SELECT Products.MasterID, 1 AS IsMaster, Products.ProductNo, NULL AS VariantProductNo
FROM Products
UNION
SELECT Products.MasterID, 0 AS IsMaster, Products.ProductNo, ProductVariants.VariantProductNo
FROM Products
INNER JOIN ProductVariants
ON Products.ID = ProductVariants.MasterID
ORDER BY MasterID, IsMaster DESC, ProductNo