sql - SQLite SELECT 与 JOIN 和 GROUP？

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

这个字符串给了我一个产品代码和销售数量。我需要添加的是，基于产品代码，该产品代码的描述。

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

谢谢！！！

Answer 1

你想把JOIN这两个表放在product_code。

你真的应该做一个LEFT JOIN捕获没有相关收据项目的产品，然后CASE在你的声明中将值SUM减少NULL到 0。

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