Question

我有一个包含审计信息的SQL表：

GroupId AuditDate   ID  FirstName   LastName
1      01/06/2011   123 Michael    Jackson
1      01/09/2010   123 M          J
1      01/06/2009   123 Mike       J

并尝试显示审核记录之间的差异：

GroupId AuditDate   ID  Attribute   From    To
1      01/06/2011   123 FirstName   M       Michael
1      01/06/2011   123 LastName    J       Jackson
1      01/09/2010   123 FirstName   Mike    M
1      01/06/2009   123 FirstName   NULL    Mike
1      01/06/2009   123 LastName    NULL    J

我正在使用以下SQL查询：

WITH result AS (
SELECT          [Current].Id, 
                [Current].GroupId, 
                [Current].AuditDate, 
                [Current].FirstName, 
                [Current].LastName
                Previous.FirstName AS PFirstName,
                Previous.LastName AS PLastName,
FROM 
    (SELECT 
        *, ROW_NUMBER() OVER(PARTITION BY GroupId ORDER BY AuditDate ASC) AS RowNumber 
    FROM 
        AuditTable  
    WHERE 
        Id = @ID
    ) AS [Current]
LEFT JOIN
    (SELECT 
        *, ROW_NUMBER() OVER(PARTITION BY GroupId ORDER BY AuditDate ASC) AS RowNumber 
    FROM 
        AuditTable
    WHERE 
        Id = @ID
    ) AS [Previous]
ON
    [Current].RowNumber = [Previous].RowNumber + 1
)

SELECT r.Id,r.GroupId, r.AuditDate 
  x.Attribute,
  x.[From],
  x.[To]
FROM result r
CROSS APPLY 
(
    VALUES
        ('FirstName', t.FirstName, t.PFirstName),
        ('LastName', t.LastName, t.PLastName),
) x (Attribute, [To], [From])
where 
    ISNULL(x.[From],'') <> ISNULL(x.[To],'') 
ORDER BY r.AuditDate asc;

是否可以合并两个选择查询以提高性能？

Answer 1

您可以使用lag()完全删除这两个子查询：

WITH result AS (
SELECT Id, 
       GroupId, 
       AuditDate, 
       FirstName, 
       LastName,
       lag(FirstName) over (PARTITION BY GroupId ORDER BY AuditDate ASC) 
          AS PFirstName,
       lag(LastName) over (PARTITION BY GroupId ORDER BY AuditDate ASC)
          AS PLastName
    FROM AuditTable  
    WHERE Id = @ID
)
...

Here is the relevant documentation

更新但是，不幸的是，这仅适用于SQL Server 2012。如果您有早期版本，则需要某种自联接。

如果你不能使用lag()，你至少应该能够将你的代码从3个查询减少到2个：在你的第一个select语句中包含行号，并且左边连接一个子查询而不是有两个子查询。我不确定这种方式或Chris Moutray的方式会更快。

WITH result AS (
SELECT ROW_NUMBER() OVER(PARTITION BY GroupId ORDER BY AuditDate ASC) AS RowNumber         
       [Current].Id, 
       [Current].GroupId, 
       [Current].AuditDate, 
       [Current].FirstName, 
       [Current].LastName
       [Previous].FirstName AS PFirstName,
       [Previous].LastName AS PLastName,
FROM AuditTable as [Current]
LEFT JOIN
    (SELECT 
        *, ROW_NUMBER() OVER(PARTITION BY GroupId ORDER BY AuditDate ASC) AS RowNumber 
    FROM 
        AuditTable
    WHERE 
        Id = @ID
    ) AS [Previous]
ON
    [Current].RowNumber = [Previous].RowNumber + 1
)

Answer 2

尝试此查询

WITH result AS (
SELECT Id, 
       GroupId, 
       AuditDate, 
       FirstName, 
       LastName,          
       ROW_NUMBER() OVER(PARTITION BY GroupId ORDER BY AuditDate ASC) AS RowNumber 
FROM AuditTable  
WHERE Id = @ID
 )
SELECT r.Id,r.GroupId, r.AuditDate,
       x.Attribute,
       x.[From],
       x.[To]
FROM result r LEFT JOIN result r2 ON r.RowNumber = r2.RowNumber + 1
CROSS APPLY (
             VALUES ('FirstName', r.FirstName, r2.FirstName),
                    ('LastName', r.LastName, r2.LastName)
             ) x (Attribute, [To], [From])
WHERE ISNULL(x.[From],'') <> ISNULL(x.[To],'') 
ORDER BY r.AuditDate ASC;

SQLFiddle上的演示

Answer 3

您可以在SQL Server 2012中使用LAG。我在这里使用UNION ALL将列拆分为行。

根据您的过滤方式和组级别，添加/修改PARTITION BY

DECLARE @foo TABLE (GroupId tinyint, AuditDate date, ID tinyint, FirstName varchar(100),  LastName varchar(100));
INSERT @foo VALUES (1, '20110601', 123, 'Michael', 'Jackson'), (1, '20100901', 123, 'M', 'J'), (1, '20090601', 123, 'Mike', 'J');

SELECT
    X.GroupId, X.AuditDate, X.ID, X.[From], X.[To]
FROM
    (
    SELECT
        F.GroupId, F.AuditDate, F.ID, 'FirstName' AS Attribute, LAG(F.FirstName) OVER (/*PARTITION BY GroupId, ID*/ ORDER BY AuditDate) AS [From], F.FirstName AS [To]
    FROM
        @foo F
    UNION ALL
    SELECT
        F.GroupId, F.AuditDate, F.ID, 'LastName' AS Attribute, LAG(F.LastName) OVER (/*PARTITION BY GroupId, ID*/ ORDER BY AuditDate) AS [From], F.LastName AS [To]
    FROM
        @foo F
    ) X
WHERE
    ISNULL(X.[From], '') <> ISNULL(X.[To],  '')
ORDER BY
    X.AuditDate DESC, X.Attribute

SQL交叉申请

3 个答案: