How to Find Nth Row in Partition Given a Condition SQL?

Question

Hello I have the following tables:

Brand Columns: Brand_ID(Primary Key), Company Name

Orders Columns: ORDER_ID(Primary Key), USER_ID, BRAND_ID(Foreign Key), DATE

I'm trying to get the 3rd order for each USER_ID, placed after 2018, if the order is from COMPANY_NAME X. I'm kind of lost on how to proceed. I've tried using a window function, but I don't think it lets me use a WHERE function inside?

I have the following code:

SELECT *
FROM (
    SELECT O.*,
        row_number() OVER (
            PARTITION BY USER_ID 
            WHERE DATE >= '2018/01/01'
            ORDER BY DATE
            ) as rank
    FROM Orders O
    ) O
JOIN Brands B ON O.BRAND_ID = B.BRAND_ID
WHERE O.rank = 3 AND B.COMPANY_NAME = 'X';

Answer 1

You want to filter in a where clause -- which is not part of the window function specification:

SELECT *
FROM (SELECT O.*,
             row_number() OVER (PARTITION BY USER_ID 
                                ORDER BY DATE
                               ) as rank
      FROM Orders O
      WHERE DATE >= '2018-01-01'
     ) O JOIN
     Brands B
     ON O.BRAND_ID = B.BRAND_ID
WHERE O.rank = 3 AND B.COMPANY_NAME = 'X';