sales-analysis-ii.sql

-- Table: Product

-- +--------------+---------+
-- | Column Name  | Type    |
-- +--------------+---------+
-- | product_id   | int     |
-- | product_name | varchar |
-- | unit_price   | int     |
-- +--------------+---------+
-- product_id is the primary key of this table.
-- Table: Sales

-- +-------------+---------+
-- | Column Name | Type    |
-- +-------------+---------+
-- | seller_id   | int     |
-- | product_id  | int     |
-- | buyer_id    | int     |
-- | sale_date   | date    |
-- | quantity    | int     |
-- | price       | int     |
-- +------ ------+---------+
-- This table has no primary key, it can have repeated rows.
-- product_id is a foreign key to Product table.
-- Write an SQL query that reports the buyers who have bought S8 but not iPhone. Note that S8 and iPhone are products present in the Product table.

-- The query result format is in the following example:

-- Product table:
-- +------------+--------------+------------+
-- | product_id | product_name | unit_price |
-- +------------+--------------+------------+
-- | 1          | S8           | 1000       |
-- | 2          | G4           | 800        |
-- | 3          | iPhone       | 1400       |
-- +------------+--------------+------------+

-- Sales table:
-- +-----------+------------+----------+------------+----------+-------+
-- | seller_id | product_id | buyer_id | sale_date  | quantity | price |
-- +-----------+------------+----------+------------+----------+-------+
-- | 1         | 1          | 1        | 2019-01-21 | 2        | 2000  |
-- | 1         | 2          | 2        | 2019-02-17 | 1        | 800   |
-- | 2         | 1          | 3        | 2019-06-02 | 1        | 800   |
-- | 3         | 3          | 3        | 2019-05-13 | 2        | 2800  |
-- +-----------+------------+----------+------------+----------+-------+

-- Result table:
-- +-------------+
-- | buyer_id    |
-- +-------------+
-- | 1           |
-- +-------------+
-- The buyer with id 1 bought an S8 but didn't buy an iPhone. The buyer with id 3 bought both.

# V0
# NOTE : how we deal with `NOT IN` here
select distinct buyer_id
from Sales inner join Product
where Sales.product_id = Product.product_id
    and product_name = 'S8'
    and buyer_id not in
    (select distinct buyer_id
    from Sales inner join Product
    where Sales.product_id = Product.product_id
        and product_name = 'iPhone')

# V1
# https://code.dennyzhang.com/sales-analysis-ii
select distinct buyer_id
from Sales inner join Product
where Sales.product_id = Product.product_id
    and product_name = 'S8'
    and buyer_id not in
    (select distinct buyer_id
    from Sales inner join Product
    where Sales.product_id = Product.product_id
        and product_name = 'iPhone')

# V2 
# Time:  O(m + n)
# Space: O(m + n)
SELECT DISTINCT buyer_id 
FROM   sales 
       INNER JOIN product 
         ON sales.product_id = product.product_id 
WHERE  product.product_name = "s8" 
       AND buyer_id NOT IN (SELECT DISTINCT buyer_id 
                            FROM   sales 
                                   INNER JOIN product 
                                     ON sales.product_id = product.product_id 
                            WHERE  product.product_name = "iphone");