Question

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我想按年份和月份查询OrderDate组，因此可以将同月的数据添加到一起

非常感谢你的帮助

Answer 1

您需要从日期中提取年份和月份，并使用select和group by列中的年份和月份。如何执行此操作在很大程度上取决于数据库。许多支持称为year()和month()的函数。

然后你需要按你想要的字段聚合。像这样：

SELECT YEAR(so.OrderDate) as yyyy, MONTH(so.OrderDate) as mm,      
       b.BookID, b.title,
       COUNT(so.ShopOrderID) AS "Total number of order",
       SUM(ol.Quantity) AS "Total quantity",
       SUM(ol.UnitSellingPrice * ol.Quantity  AS "Total order value",
       SUM(b.Price * ol.Quantity) AS "Total retail value" 
FROM ShopOrder so JOIN
     Orderline ol
     ON ol.ShopOrderID = so.ShopOrderID JOIN
     Book b
     ON b.BookID = ol.BookID JOIN
     Publisher p
     ON p.PublisherID = b.PublisherID
WHERE p.name = 'Addison Wesley'
GROUP BY YEAR(so.OrderDate), MONTH(so.OrderDate), b.BookID, b.title
ORDER BY MIN(so.OrderDate)

请注意，使用表别名可以使查询更容易编写和读取。

以上在MySQL，DB2和SQL Server中有效。在Postgres和Oracle中，to_char(so.OrderDate, 'YYYY-MM')。

Answer 2

对于组，您可以使用datepart函数

GROUP BY (DATEPART(yyyy, ShopOrder.OrderDate), DATEPART(mm, ShopOrder.OrderDate))

Answer 3

你应该聚合

, Orderline.UnitSellingPrice * Orderline.Quantity  AS "Total order value"
, book.Price * Orderline.Quantity AS "Total retail value"

或者您将count(...)个值等于1。 YEAR(myDate)的{{1}}和MONTH(myDate)是group by函数的便捷快捷方式（在MS SQL Server上）

SQL按日期和月份排序日期

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