Leetcode Problem 1158. Market Analysis I

1158. Market Analysis I

Leetcode Solutions

Left Join and Aggregation

Start with the Users table as the base for the query to ensure all users are included in the results.
Perform a LEFT JOIN with the Orders table on the condition that the user_id matches the buyer_id and the order_date is within the year 2019.
Use the COUNT function to count the number of orders for each user, resulting in the number of orders made by each user as a buyer in 2019.
Group the results by user_id to consolidate orders per user.
Select the user_id (aliased as buyer_id), join_date, and the count of orders as orders_in_2019.
Sort the final result by user_id to organize the output.

erDiagram
    Users {
        int user_id
        date join_date
        varchar favorite_brand
    }
    Orders {
        int order_id
        date order_date
        int item_id
        int buyer_id
        int seller_id
    }
    Items {
        int item_id
        varchar item_brand
    }
    Users ||--o{ Orders : ""
    Orders }|--|| Items : ""

Subquery and Group By

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Leetcode Problem 1158. Market Analysis I

Leetcode Solutions

Left Join and Aggregation

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Query Steps

Code Implementation

Subquery and Group By

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