Not a simple comparison between the two count()
My solution cover the situation that the product_keys in customer table are out of those in product #table\n\nselect customer_id\nfrom ( \n    select p.product_
#My solution cover the situation that the product_keys in customer table are out of those in product #table\n\nselect customer_id\nfrom ( \n    select p.product_key, c.customer_id\n    from product p\n    left join customer c on c.product_key = p.product_key ) t\ngroup by customer_id\nhaving count(distinct product_key) = (select count(*) from product)
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