SOLUTION WITH SIMPLE JOIN ( SQL SERVER )
Intuition\r\n Describe your first thoughts on how to solve this problem. \r\n\r\n# Approach\r\n Describe your approach to solving the problem. \r\n\r\n# Complex
# Intuition\r\n<!-- Describe your first thoughts on how to solve this problem. -->\r\n\r\n# Approach\r\n<!-- Describe your approach to solving the problem. -->\r\n\r\n# Complexity\r\n- Time complexity:\r\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\r\n\r\n- Space complexity:\r\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\r\n\r\n# Code\r\n```\r\n/* Write your T-SQL query statement below */\r\n\r\n\r\n\r\n    SELECT \r\n        T2.customer_id\r\n    FROM\r\n        product T1 \r\n    INNER JOIN\r\n        (\r\n            SELECT\r\n                DISTINCT *\r\n            FROM\r\n                Customer\r\n         ) T2 ON T2.product_key = T1.product_key\r\n    GROUP BY\r\n        T2.customer_id\r\n    HAVING  COUNT(T1.product_key) = (SELECT COUNT(product_key) FROM Product)\r\n\r\n```
['MS SQL Server']