SQL查找上一行和当前行之间的差异

Question

我试图找出当前行和上一行之间的差异。但是，我收到以下错误消息：

无法绑定多部分标识符“tableName”。

不确定如何修复错误。

谢谢！

输出应如下所示：

columnOfNumbers     Difference
      1               NULL
      2               1
      3               1
      10              7
      12              2
      ....            ....

代码：

USE DATABASE;

WITH CTE AS 
(SELECT 
    ROW_NUMBER() OVER (PARTITION BY tableName ORDER BY columnOfNumbers) ROW,
    columnOfNumbers
    FROM tableName)
SELECT
    a.columnOfNumbers
FROM
    CTE a
    LEFT JOIN CTE b
    ON a.columnOfNumbers = b.columnOfNumbers AND a.ROW = b.ROW + 1

Answer 1

如果您在 SQL Server 2012+ 中，则可以使用 LAG。

 SELECT columnOfNumbers
       ,columnOfNumbers - LAG(columnOfNumbers, 1) OVER (ORDER BY columnOfNumbers)
   FROM tableName

注意：LAG的第三个可选参数为：

默认

当 scalar_expression 在 offset 为 NULL 时返回的值。 如果未指定默认值，则返回 NULL。默认可以 列、子查询或其他表达式，但不能是分析 功能。 default 必须与 scalar_expression 类型兼容。

Answer 2

见sqlFiddle

;WITH tblDifference AS
(
    SELECT ROW_NUMBER() OVER(ORDER BY id) AS RowNumber, columnOfNumbers 
    FROM tableName
)

SELECT cur.columnOfNumbers, cur.columnOfNumbers - previous.columnOfNumbers
FROM tblDifference cur
LEFT OUTER JOIN tblDifference previous
ON cur.RowNumber = previous.RowNumber + 1

Answer 3

我认为您不需要partition by 声明：

WITH CTE AS (
      SELECT ROW_NUMBER() OVER (ORDER BY columnOfNumbers) as ROW,
             columnOfNumbers
      FROM tableName
     )
SELECT a.columnOfNumbers, a.columnOfNumbers - b.columnOfNumbers
FROM CTE a LEFT JOIN
     CTE b
     ON a.ROW = b.ROW + 1;

如果你确实需要它，你应该输入一个列名而不是一个表名。