连接外键表

Question

I have the following three tables:

• Product
• Purchase (contains ProductID as foreign key)
• Sale (contain ProductID as foreign key as well)

I want to form query joining these 3 tables where my result is the product name, purchased, and sold.

Product Name - (from Products table)

Purchased - (Number of occurences in Purchase table according to ProductID)

Sold - (Number of occurences in Sale Table according to ProductID)

Can you please set me on the right track by giving me hints and I'll complete by myself?

Answer 1

I'm betting this will get deleted...but hopefully you see this before it does. The following is really helpful in understanding the differences in the SQL JOINS. . This answer or Kyle's answers is all you need to solve your question.

Source: INNER JOIN, LEFT/RIGHT OUTER JOIN

Answer 2

As far as a hint, you need to use a join of some sort ( join fundamentals ).

A possible answer is below:

Select p.ProductName, pu.Purchased, s.Sold
From Products p 
INNER JOIN Purchase pu on p.ProductID = pu.ProductID
INNER JOIN Sale s on s.ProductID = p.ProductID