[英]SQL Find difference between previous and current row
我试图找到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
.... ....
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
如果您使用的是SQL Server 2012+,则可以使用LAG。
SELECT columnOfNumbers
,columnOfNumbers - LAG(columnOfNumbers, 1) OVER (ORDER BY columnOfNumbers)
FROM tableName
注意:LAG的可选第三个参数是:
默认
当偏移处的scalar_expression为NULL时返回的值。 如果未指定默认值,则返回NULL。 default可以是列,子查询或其他表达式,但它不能是分析函数。 default必须与scalar_expression类型兼容。
;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
我不认为你需要partition by
语句:
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;
如果确实需要它,则应该输入列名而不是表名。
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