Question

我一直在尝试编写存储过程，我可以使用合并以下条件执行UpSert

如果记录存在，则将目标的EndDate更改为昨天的日期，即当前日期 - 1
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，它将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

如何在匹配列时执行更新现有记录和添加新记录

请有人在TSQL中解释合并的执行流程，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

每次在Merge中都会执行以上所有3个条件，或者每次只执行匹配条件

先谢谢

Answer 1

这不是MERGE的意图（在同一条款中更新和插入）。要实现此目的，您可以使用OUTPUT子句仅获取所有更新的记录。 MERGE / OUTPUT组合非常挑剔。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。然后你将那些背对着SOURCE进行匹配来进行INSERT。您不会被允许直接将输出结果加入源代码，甚至可以在WHERE中用作相关子查询。

设置一些示例数据

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

您可以在OUTPUT的末尾使用MERGE让它返回目标记录的修改记录，并且通过加入$action，您还可以获得它是否是插入，更新或删除。

但是，MERGE / OUTPUT的结果集无法直接与SOURCE表连接，因此您可以执行INSERT，因为您只能获得TARGET记录。您也无法使用SOURCE表中相关子查询中OUTPUT的结果。最简单的方法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MERGE的输出并过滤到只获取更新的TARGET记录，那么您可以通过仅过滤属于的部分的SOURCE记录来执行未完成的INSERT MERGE更新。

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?)
    )

<强>输出继电器

这是更改后样本记录的输出。您进行了预期的TARGET更改。

-- Show output
SELECT * FROM @tblEmployee

Answer 2

遵循已接受答案的想法，这在Sql Server 2008 r2中也可以正常工作：

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'

您可以使用不同的值。

在TSQL-Merge

2 个答案: