使用JOIN和GROUP的SQLite SELECT？

Question

我正在尝试根据以下字符串的结果添加一列：

SELECT product_code AS "Product Code", SUM(quantity) AS "Quantity" 
FROM receipts_items
GROUP BY product_code
ORDER BY SUM(quantity) DESC

此字符串为我提供了产品代码和销售数量。根据产品代码，我需要添加的是产品代码的描述。

product_code和description列在同一个表中“产品” 数量在另一个表“receipts_items”

感谢!!!

Answer 1

您希望JOIN product_code上的两个表格LEFT JOIN。

您确实应该使用CASE来捕获没有关联收据项的产品，然后在SUM中添加NULL语句，将SELECT p.product_code AS "Product Code", p.description AS "Description", SUM(CASE WHEN ri.quantity IS NULL THEN 0 ELSE ri.quantity END) AS "Quantity" FROM products AS p LEFT JOIN receipts_items AS ri ON ri.product_code = p.product_code GROUP BY p.product_code ORDER BY SUM(ri.quantity) DESC 值减少为0。

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