✔✔✔tricky but easy solution with stepwise explanation⚡MS SQL Server | MySQL | Oracle | PostgreSQL
Code - MS SQL Server | MySQL | Oracle | PostgreSQL\n\nSELECT c.customer_id\nFROM Customer AS c\nGROUP BY c.customer_id\nHAVING COUNT(DISTINCT c.product_key) = (
# Code - MS SQL Server | MySQL | Oracle | PostgreSQL\n```\nSELECT c.customer_id\nFROM Customer AS c\nGROUP BY c.customer_id\nHAVING COUNT(DISTINCT c.product_key) = (SELECT COUNT(product_key) FROM Product)\n```\n\n# Explanation\n- step 1\n```\nGROUP BY c.customer_id\n```\nfirst, group the records based on unique customer IDs\n\n- step 2\n```\nHAVING COUNT(DISTINCT c.product_key) = (SELECT COUNT(product_key) FROM Product)\n```\nthen, include only those customer IDs where the count of distinct product keys associated with each customer is equal to the total count of product keys in the "Product" table.
['MySQL', 'Oracle', 'MS SQL Server']