README_EN.md

1045. Customers Who Bought All Products

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Description

Table: Customer

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| customer_id | int     |
| product_key | int     |
+-------------+---------+
There is no primary key for this table. It may contain duplicates.
product_key is a foreign key to Product table.

 

Table: Product

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| product_key | int     |
+-------------+---------+
product_key is the primary key column for this table.

 

Write an SQL query to report the customer ids from the Customer table that bought all the products in the Product table.

Return the result table in any order.

The query result format is in the following example.

 

Example 1:

Input: 
Customer table:
+-------------+-------------+
| customer_id | product_key |
+-------------+-------------+
| 1           | 5           |
| 2           | 6           |
| 3           | 5           |
| 3           | 6           |
| 1           | 6           |
+-------------+-------------+
Product table:
+-------------+
| product_key |
+-------------+
| 5           |
| 6           |
+-------------+
Output: 
+-------------+
| customer_id |
+-------------+
| 1           |
| 3           |
+-------------+
Explanation: 
The customers who bought all the products (5 and 6) are customers with IDs 1 and 3.

Solutions

SQL

# Write your MySQL query statement below
SELECT
    customer_id
FROM
    Customer
GROUP BY
    customer_id
HAVING
    COUNT(DISTINCT(product_key)) = (
        SELECT
            COUNT(1)
        FROM
            Product
    );