Easy Soution with Step by Step Explanation
Intuition\nImagine you have a list of all the sales made by a store, and each sale has information about the product sold, the date of the sale, how many of the
# Intuition\nImagine you have a list of all the sales made by a store, and each sale has information about the product sold, the date of the sale, how many of the product were sold, and the price of each unit. Now, we want to figure out which products were sold more than once on the same day and how much money was made from those products.\n\n# Approach\nHere\'s how we can approach the problem using SQL (a language for working with databases):\n\n1. First, we need to look at the sales data and identify products that were sold in their first year. We do this by finding the minimum year for each product.\n\n1. Once we know which products were sold in their first year, we can use that information to calculate the total sales amount for each of these products on each day they were sold.\n\n1. Finally, we\'ll add up the total sales amounts for all the products that were sold more than once on the same day.\n\n# **SQL Query Steps:**\nHere\'s the SQL query that accomplishes the above steps:\n\n**Subquery (finding first year sales):**\n\n1. We create a small "temporary" table by using a subquery. This table will contain the product_id and the minimum year of sale for each product. This subquery groups the sales data by product_id and finds the minimum year for each product using the MIN() function.\n1. So, in this temporary table, we have one row for each product, showing which year it was first sold.\n\n**Main Query (calculating total sales amount):**\n\n1. We use the main query to retrieve the product_id, year, quantity sold, and price for all sales data.\n1. We then filter the results to only include rows where the product was sold in its first year. We do this by matching the product_id and year with the product_id and minimum year from the temporary table we created in the subquery.\n\n**Summing up the total sales amount:**\n\n1. With the filtered results, we now have the sales data for products that were sold in their first year. We calculate the total sales amount for each product on each day they were sold. This is done by multiplying the quantity sold with the price per unit for each sale.\n1. Finally, we add up the total sales amounts for all the products that were sold more than once on the same day.\n\n# Complexity\n- Time complexity:\nThe time complexity is $$O(NlogN)$$, where N is the number of rows in the "Sales" table. The main contributor to this time complexity is the subquery, which involves grouping and finding the minimum year for each product_id, and this operation takes $$O(NlogN)$$ time.\n\n\n- Space complexity:\nThe space complexity is $$O(N)$$, where N is the number of unique products in the "Sales" table. The subquery creates a temporary table with one row for each unique product_id, leading to O(N) space usage.\n\n\n# Code\n```\n# Write your MySQL query statement below\n\nselect\n    product_id,\n    year as first_year,\n    quantity,\n    price\nfrom Sales\nwhere (product_id, year) in (select product_id, min(year) from Sales group by 1)\n\n```
['Database', 'MySQL']