Leetcode Problem 1045. Customers Who Bought All Products

1045. Customers Who Bought All Products

Leetcode Solutions

Counting Distinct Products Bought by Each Customer

Algorithm

Select the customer_id from the Customer table.
Group the results by customer_id to prepare for counting the distinct products each customer bought.
Count the distinct product_key for each grouped customer_id.
Use the HAVING clause to filter only those customers whose count of distinct product_key is equal to the total number of products in the Product table. This total is obtained by a subquery that counts all entries in the Product table.
Return the customer_id of customers who meet the criteria.


erDiagram
    Customer {
        int customer_id
        int product_key
    }

    Product {
        int product_key
    }

    Customer }|--|| Product : has

Using Nested Subquery with Cartesian Product

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Leetcode Problem 1045. Customers Who Bought All Products

Leetcode Solutions

Counting Distinct Products Bought by Each Customer

Solution Idea

Query Steps

Code Implementation

Algorithm

Using Nested Subquery with Cartesian Product

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