4

我一直在尝试编写一个存储过程，我可以在其中使用带有以下条件的 Merge 执行 UpSert

  1. 如果记录存在，则将目标的结束日期更改为昨天，即现在 - 1

  2. 如果记录不存在，则插入新记录

这是我在 SP 中使用的表 tblEmployee

CREATE TABLE tblEmployee
(
    [EmployeeID] [int] IDENTITY(1,1) NOT NULL, 
    [Name] [varchar](10) NOT NULL,  
    [StartDate] [date] NOT NULL,
    [EndDate] [date] NOT NULL
)

这是我的 SP，它以 UDTT 作为输入参数

CREATE PROCEDURE [dbo].[usp_UpsertEmployees]
@typeEmployee typeEmployee READONLY -- It has same column like tblEmployye except EmployeeID
AS
BEGIN
    SET NOCOUNT ON;      

    MERGE INTO tblEmployee AS TARGET
    USING @typeEmployee AS SOURCE
    ON TARGET.Name = SOURCE.Name 

    WHEN MATCHED and TARGET.StartDate < SOURCE.StartDate
    THEN 

            --First Update Existing Record EndDate to Previous Date as shown below 
            UPDATE 
            set TARGET.EndDate = DATEADD(day, -1, convert(date, SOURCE.StartDate))

            -- Now Insert New Record 
            --INSERT VALUES(SOURCE.Name, SOURCE.StartDate, SOURCE.EndDate);

    WHEN NOT MATCHED by TARGET 
    THEN
            INSERT VALUES(SOURCE.Name, SOURCE.StartDate, SOURCE.EndDate);

    SET NOCOUNT OFF;        
END

当列匹配时，如何同时执行更新现有记录和添加新记录

请有人解释一下TSQL中合并的执行流程，即

    WHEN MATCHED --Will this Execute Everytime

    WHEN NOT MATCHED by TARGET -- Will this Execute Everytime

    WHEN NOT MATCHED by SOURCE -- Will this Execute Everytime

每次合并中都会执行以上 3 个条件还是每次只执行匹配条件

提前致谢

4

2 回答 2

8

这不是MERGE应该做的（在同一子句中更新和插入）。为此，您可以使用该OUTPUT子句仅获取所有更新的记录。/组合非常挑剔MERGE。OUTPUT您的OUTPUT更新实际上是已更新的 TARGET 记录，因此您必须在 temp/table 变量中启动 TARGET 记录。然后你将它们与 SOURCE 匹配以进行 INSERT。不允许您将输出结果直接连接回源，甚至不能用作WHERE.

设置一些样本数据

下面的代码只是设置了一些示例数据。

-- Setup sample data
DECLARE @typeEmployee TABLE (
    [Name] [varchar](10) NOT NULL,  
    [StartDate] [date] NOT NULL,
    [EndDate] [date] NOT NULL
)
DECLARE @tblEmployee TABLE (
    [EmployeeID] [int] IDENTITY(1,1) NOT NULL, 
    [Name] [varchar](10) NOT NULL,  
    [StartDate] [date] NOT NULL,
    [EndDate] [date] NOT NULL   
)
INSERT @tblEmployee VALUES ('Emp A', '1/1/2016', '2/1/2016')
INSERT @typeEmployee VALUES ('Emp A', '1/5/2016', '2/2/2016'), ('Emp B', '3/1/2016', '4/1/2016')

存储过程的更新

您可以OUTPUT在 a 的末尾使用MERGE它来返回目标记录的修改记录，并且通过包含$action，您还将获得它是插入、更新还是删除。

但是，来自MERGE/的结果集OUTPUT不能直接连接到 SOURCE 表，因此您可以执行您的操作INSERT，因为您只能获取 TARGET 记录。您也不能使用OUTPUT来自 SOURCE 表的内部相关子查询的结果。最简单的事情是使用临时表或表变量来捕获输出。

-- Logic to do upsert
DECLARE @Updates TABLE (
    [Name] [varchar](10) NOT NULL,  
    [StartDate] [date] NOT NULL,
    [EndDate] [date] NOT NULL
)

INSERT @Updates
    SELECT
        Name,
        StartDate,
        EndDate
    FROM (
        MERGE INTO @tblEmployee AS TARGET
        USING @typeEmployee AS SOURCE
            ON TARGET.Name = SOURCE.Name 
        WHEN MATCHED AND TARGET.StartDate < SOURCE.StartDate
        THEN
            --First Update Existing Record EndDate to Previous Date as shown below 
            UPDATE SET
                EndDate = DATEADD(DAY, -1, CONVERT(DATE, SOURCE.StartDate))
        WHEN NOT MATCHED BY TARGET -- OR MATCHED AND TARGET.StartDate >= SOURCE.StartDate -- Handle this case?
        THEN
            INSERT VALUES(SOURCE.Name, SOURCE.StartDate, SOURCE.EndDate)
        OUTPUT $action, INSERTED.Name, INSERTED.StartDate, INSERTED.EndDate
        -- Use the MERGE to return all changed records of target table
    ) AllChanges (ActionType, Name, StartDate, EndDate)
    WHERE AllChanges.ActionType = 'UPDATE' -- Only get records that were updated

既然您已经捕获了 的输出MERGE并进行了过滤以仅获取更新的 TARGET 记录，那么您可以INSERT通过仅过滤作为更新一部分的 SOURCE 记录来完成您的工作MERGE。

INSERT @tblEmployee
    SELECT
        SOURCE.Name,
        SOURCE.StartDate,
        SOURCE.EndDate
    FROM @typeEmployee SOURCE
    WHERE EXISTS (
        SELECT *
        FROM @Updates Updates
        WHERE Updates.Name = SOURCE.Name
            -- Other join conditions to ensure 1:1 match against SOURCE (start date?)
    )

输出

这是更改后的样本记录的输出。进行了预期的 TARGET 更改。

-- Show output
SELECT * FROM @tblEmployee
于 2016-07-12T13:12:41.743 回答
1

按照接受的答案的想法，这在 Sql server 2008 r2 中也适用：

create table Test1 (
  Id int, FromDate date, ThruDate date, Value int
)


insert into dbo.Test1
 (Id, FromDate, ThruDate, [Value])
select 
  t.Id, t.FromDate, T.ThruDate, t.Value * 100
from (

MERGE  dbo.Test1 AS Target
 USING (
         select 1 as Id, '2000-01-01' as FromDate, '2000-12-31' as ThruDate, 2 as Value
       ) AS Source
    ON (  target.id = source.Id
        )
WHEN MATCHED
THEN
  UPDATE SET Target.[Id] = Source.[Id]
           , Target.[FromDate] = Source.[FromDate]
           , Target.[ThruDate] = Source.[ThruDate]
           , Target.[Value] = Source.[Value]
WHEN NOT MATCHED BY TARGET
THEN
  INSERT ([Id]
        , [FromDate]
        , [ThruDate]
        , [Value])
  VALUES (Source.[Id]
        , Source.[FromDate]
        , Source.[ThruDate]
        , Source.[Value])
OUTPUT $ACTION as Act, Inserted.*
) t
where t.Act  = 'Update'

你可以玩不同的价值观。

于 2018-07-26T19:41:06.090 回答