simple solution
\nSELECT customer_id from Customer\ngroup by customer_id\nhaving count(distinct product_key) = \n(\nselect count(distinct product_key) from Product\n)\n\n
```\nSELECT customer_id from Customer\ngroup by customer_id\nhaving count(distinct product_key) = \n(\nselect count(distinct product_key) from Product\n)\n\n```
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