How to display unique product properties by category ID using SQL query?

Question

SQL

Now I'm solving the last problem in the SQL and database test, which talks about a database that has 4 tables:

• table of product categories category (id, name);
  
• product table product (id,category_id,name,price);
  
• property table property (id, name);
  
• table of goods property values ​​property_value (product_id,property_id,value);
  

And the problem lies in the condition itself:

Get a list of names of unique product properties by category name (the property should be only for 1 product in the category)

This is the first time I have encountered such a task of this kind (have you ever encountered this?) and I want to deal with an SQL query that allows you to get a unique list of product properties by category ID. Since I have about a year of experience with SQL, I did not play around with more complex queries. Do you have a variant of such a query, while using SELECT DISTINCT, so that I can write it as an answer?

Answer 1

Well, here it turns out you need to get all the properties of goods for a particular category, count their number, grouping them by property id first, and then take only those where the number is equal to one. Looks simple enough. But maybe I misunderstood the problem statement.