SQL 分组和运行日期范围内未清项的总计

Question

为了简单起见，我有一个项目表，其中包含 ItemID、StartDate 和 EndDate 项目列表。

ItemID     StartDate     EndDate
1          1/1/2011      1/15/2011
2          1/2/2011      1/14/2011
3          1/5/2011      1/17/2011
...

我的目标是能够将此表连接到具有顺序日期列表的表中， 并说出在特定日期有多少项目是打开的，以及有多少项目是累积打开的。

Date      ItemsOpened     CumulativeItemsOpen
1/1/2011  1               1
1/2/2011  1               2
...

我可以看到如何使用WHILE 循环来完成此操作， 但这会影响性能。我想知道如何 这可以通过基于集合的方法来完成吗？

Answer 1

SELECT COUNT(CASE WHEN d.CheckDate = i.StartDate THEN 1 ELSE NULL END)
         AS ItemsOpened
     , COUNT(i.StartDate)
         AS ItemsOpenedCumulative
FROM Dates AS d
  LEFT JOIN Items AS i
    ON d.CheckDate BETWEEN i.StartDate AND i.EndDate
GROUP BY d.CheckDate

Answer 2

这可能会给你想要的东西

SELECT DATE, 
    SUM(ItemOpened) AS ItemsOpened, 
    COUNT(StartDate) AS ItemsOpenedCumulative
FROM
    (
    SELECT d.Date, i.startdate, i.enddate,
        CASE WHEN i.StartDate = d.Date THEN 1 ELSE 0 END AS ItemOpened
    FROM Dates d
    LEFT OUTER JOIN Items i ON d.Date BETWEEN i.StartDate AND i.EndDate
    ) AS x
GROUP BY DATE
ORDER BY DATE

这假定您的日期值是 DATE 数据类型。或者，日期是没有时间值的 DATETIME。

Answer 3

您可能会发现这很有用。递归部分可以用一张桌子代替。为了证明它有效，我必须填充某种日期表。可以看到，实际的sql很短很简单。

DECLARE @i table (itemid INT, startdate DATE, enddate DATE)

INSERT @i VALUES (1,'1/1/2011', '1/15/2011') 
INSERT @i VALUES (2,'1/2/2011', '1/14/2011')
INSERT @i VALUES (3,'1/5/2011', '1/17/2011') 

DECLARE @from DATE
DECLARE @to DATE
SET @from = '1/1/2011'
SET @to = '1/18/2011'

-- the recusive sql is strictly to make a datelist between @from and @to
;WITH cte(Date) 
AS ( 
SELECT @from DATE 
UNION ALL 
SELECT DATEADD(day, 1, DATE) 
FROM cte ch     
WHERE DATE < @to 
) 
SELECT cte.Date, sum(case when cte.Date=i.startdate then 1 else 0 end) ItemsOpened, count(i.itemid) ItemsOpenedCumulative 
FROM cte 
left join @i i on cte.Date between i.startdate and i.enddate
GROUP BY cte.Date
OPTION( MAXRECURSION 0)

Answer 4

如果您使用的是 SQL Server 2005+，则可以使用 recursive CTE 来获取运行总计，并借助 ranking 函数 ROW_NUMBER() 的额外帮助，如下所示：

WITH grouped AS (
  SELECT
    d.Date,
    ItemsOpened = COUNT(i.ItemID),
    rn = ROW_NUMBER() OVER (ORDER BY d.Date)
  FROM Dates d
    LEFT JOIN Items i ON d.Date BETWEEN i.StartDate AND i.EndDate
  GROUP BY d.Date
  WHERE d.Date BETWEEN @FilterStartDate AND @FilterEndDate
),
cumulative AS (
  SELECT
    Date,
    ItemsOpened,
    ItemsOpenedCumulative = ItemsOpened
  FROM grouped
  WHERE rn = 1
  UNION ALL
  SELECT
    g.Date,
    g.ItemsOpened,
    ItemsOpenedCumulative = g.ItemsOpenedCumulative + c.ItemsOpened
  FROM grouped g
    INNER JOIN cumulative c ON g.Date = DATEADD(day, 1, c.Date)
)
SELECT *
FROM cumulative