sales-analysis-i.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 best seller by total sales price, If there is a tie, report them all.

-- 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         | 2          | 3        | 2019-06-02 | 1        | 800   |
-- | 3         | 3          | 4        | 2019-05-13 | 2        | 2800  |
-- +-----------+------------+----------+------------+----------+-------+

-- Result table:
-- +-------------+
-- | seller_id   |
-- +-------------+
-- | 1           |
-- | 3           |
-- +-------------+
-- Both sellers with id 1 and 3 sold products with the most total price of 2800.

# V0 
select seller_id
from Sales
group by seller_id
having sum(price) = (
    select sum(price)
    from Sales
    group by seller_id
    order by sum(price) desc
    limit 1)

# V1 
# https://code.dennyzhang.com/sales-analysis-i
select seller_id
from Sales
group by seller_id
having sum(price) = (
    select sum(price)
    from Sales
    group by seller_id
    order by sum(price) desc
    limit 1)

# V2 
# Time:  O(n)
# Space: O(n)
SELECT seller_id 
FROM   sales 
GROUP  BY seller_id 
HAVING Sum(price) = (SELECT Sum(price) 
                     FROM   sales 
                     GROUP  BY seller_id 
                     ORDER  BY Sum(price) DESC 
                     LIMIT  1) 
ORDER  BY NULL