Question

我有一个包含以下三列的表格：

value date id

对于每个ID，我想使用订购日期确定第一个值。这是有效的方法吗？：

    ;with cte as
    (
        select 
            id
            ,date
            ,value
            ,ROW_NUMBER() OVER (PARTITION BY id ORDER BY date asc) AS RN 
        from Bla
where value is not null
    )
    select 
        * 
    from cte
    where RN = 1

Answer 1

是的，这是一种有效的方法。我会以相同的方式进行操作，也许一开始就没有星号，也没有分号（因为我也不用句号来开始一个句子）：

WITH 
  cte (id, [date], [value], RN) AS (
    SELECT id, [date], [value],
      ROW_NUMBER() OVER (PARTITION BY id ORDER BY [date])
    FROM Bla
    WHERE [value] IS NOT NULL
  )
SELECT id, [date], [value]
FROM cte
WHERE RN = 1;

Answer 2

另一种方法是使用TOP 1 WITH TIES，对记录进行如下排序：

SELECT TOP 1 WITH TIES id, [date], [value]
FROM BLA
ORDER BY ROW_NUMBER() OVER(PARTITION BY ID ORDER BY 
    CASE WHEN [value] IS NULL THEN '2525-12-31' ELSE [date] END)

获取值不为null的第一个条目SQL Server 2012

2 个答案: