mysql - 跨多个表的 SQL 条件求和

Question

我有以下三个表

1.产品大师（下午）

• 产品代码
• 产品名称
• Product_Category（书籍、文具、期刊、杂志）

2.订单大师（om）

• Order_ID
• 订单号
• 订购日期

3.订单行（ol）

• Order_Line_ID
• Order_ID
• 产品代码
• 数量
• 数量

现在我需要记录集中的以下列：

om.order_no, om.order_date, sum(ol.qty) for Books, sum(ol.amount) for Books, sum(ol.qty) for Stationary, sum(ol.amount) for Stationary, sum(ol.qty)用于期刊，sum(ol.amount) 用于期刊，sum(ol.qty) 用于杂志，sum(ol.amount) 用于杂志。

请帮助编写条件总和。谢谢。

Answer 1

试试这个，

SELECT  a.Order_NO,
        a.Order_Date,
        SUM(CASE WHEN c.Product_Category = 'Books' THEN b.Qty ELSE 0 END) totalBooks,
        SUM(CASE WHEN c.Product_Category = 'Books' THEN b.Amount ELSE 0 END) totalBooks_Amount,
        SUM(CASE WHEN c.Product_Category = 'Stationary' THEN b.Qty ELSE 0 END) totalStationary,
        SUM(CASE WHEN c.Product_Category = 'Stationary' THEN b.Qty ELSE 0 END) totalStationary_Amount,
        SUM(CASE WHEN c.Product_Category = 'Journals' THEN b.Qty ELSE 0 END) totalJournals,
        SUM(CASE WHEN c.Product_Category = 'Journals' THEN b.Qty ELSE 0 END) totalJournals_Amount,
        SUM(CASE WHEN c.Product_Category = 'Magazines' THEN b.Qty ELSE 0 END) totalMagazines,
        SUM(CASE WHEN c.Product_Category = 'Magazines' THEN b.Qty ELSE 0 END) totalMagazines_Amount
FROM    OrderMaster a
        INNER JOIN OrderLines b 
            ON a.Order_ID = b.Order_ID
        INNER JOIN ProductMaster c
            ON b.Product_Code = c.Product_Code
GROUP   BY a.Order_NO, a.Order_Date