sql - 获取单个查询中记录的计数百分比

Question

引用这个问题:

Get count of items and their values in one column

如何在单个查询中获取记录计数的百分比，如下所示:

ItemId        count          Percent
------------------------------------
   1            2              33.3
   2            0                0
   3            1              16.6
   4            3              50.0            

谢谢

Answer 1

COUNT(*) OVER() 给出总计数。

编辑但实际上您需要 SUM(COUNT(MyTbl.ItemID)) OVER() 来对该列中的值求和。

SELECT Items.ItemID,
       [count] = COUNT(MyTbl.ItemID),
       [Percent] = 100.0 * COUNT(MyTbl.ItemID) / SUM(COUNT(MyTbl.ItemID)) OVER()
FROM   (VALUES (1,'N1'),
               (2,'N2'),
               (3,'N4'),
               (4,'N5')) Items(ItemID, ItemName)
       LEFT JOIN (VALUES(1),
                        (1),
                        (3),
                        (4),
                        (4),
                        (4)) MyTbl(ItemID)
         ON ( MyTbl.ItemID = Items.ItemID )
GROUP  BY Items.ItemID
ORDER  BY Items.ItemID