[MySQL] Easy solution with explanation in comment
\nSELECT\n    product_id, product_name\nFROM\n    Product\nWHERE\n\t# First, find out the product that were sold in 2019 Q1\n    product_id IN (\n        SELECT
```\nSELECT\n    product_id, product_name\nFROM\n    Product\nWHERE\n\t# First, find out the product that were sold in 2019 Q1\n    product_id IN (\n        SELECT product_id\n        FROM Sales\n        WHERE\n            sale_date BETWEEN \'2019-01-01\' AND \'2019-03-31\'\n    )\n    AND \n\t# Then, we have to eliminate the products which were sold besides 2019 Q1 \n\t# That is, we only pick those products which had never been sold "except 2019 Q1" (not between 2019/1/1 and 2019/3/31)\n    product_id NOT IN (\n        SELECT product_id\n        FROM Sales\n        WHERE\n            sale_date NOT BETWEEN \'2019-01-01\' AND \'2019-03-31\'\n    )\n```
[]