"Merge" style operation with literal values?

I have a table containing开发者_开发知识库 a student-grade relationship:

Student   Grade   StartDate   EndDate
   1        1    09/01/2009    NULL
   2        2    09/01/2010    NULL
   2        1    09/01/2009   06/15/2010

I am trying to write a stored procedure that takes Student, Grade, and StartDate, and I would like it to

1. check to make sure these values are not duplicates
2. insert the record if it's not a duplicate
3. if there is an existing student record, and it has a EndDate = NULL, then update that record with the StartDate of the new record.

For instance, if I call the procedure and pass in 1, 2, 09/01/2010, I'd like to end up with:

Student   Grade   StartDate   EndDate
   1        2    09/01/2010    NULL
   1        1    09/01/2009   09/01/2010
   2        2    09/01/2010    NULL
   2        1    09/01/2009   06/15/2010

This sounds like I could use MERGE, except that I am passing literal values, and I need to perform more than one action. I also have a wicked headache this morning and can't seem to think clearly, so I am fixating on this MERGE solution. If there is a more more obvious way to do this, don't be afraid to point it out.

You can use a MERGE even if you are passing literal values. Here's an example for your issue:

CREATE PROCEDURE InsertStudentGrade(@Student INT, @Grade INT, @StartDate DATE)
AS
BEGIN;

    MERGE StudentGrade AS tbl
     USING (SELECT @Student AS Student, @Grade AS Grade, @StartDate AS StartDate) AS row
     ON tbl.Student = Row.Student AND tbl.Grade = row.Grade
    WHEN NOT MATCHED THEN
      INSERT(Student, Grade, StartDate)
       VALUES(row.Student, row.Grade, row.StartDate)
    WHEN MATCHED AND tbl.EndDate IS NULL AND tbl.StartDate != row.StartDate THEN
      UPDATE SET
        tbl.StartDate = row.StartDate;

END;

I prefer the following, it is cleaner and easier to read and modify.

MERGE Definition.tdSection AS Target
USING
    (SELECT *
     FROM   ( VALUES
            ( 1, 1, 'Administrator', 1, GETDATE(), NULL, Current_User, GETDATE())
             ,( 2, 1, 'Admissions', 1, GETDATE(), NULL, Current_User, GETDATE())
             ,( 3, 1, 'BOM', 1, GETDATE(), NULL, Current_User, GETDATE())
             ,( 4, 1, 'CRC', 1, GETDATE(), NULL, Current_User, GETDATE())
             ,( 5, 1, 'ICM', 1, GETDATE(), NULL, Current_User, GETDATE())
             ,( 6, 1, 'System', 1, GETDATE(), NULL,Current_User, GETDATE())
             ,( 7, 1, 'Therapy', 1, GETDATE(), NULL, Current_User, GETDATE()) 
            )
            AS s (SectionId
                  ,BusinessProcessId
                  ,Description, Sequence
                  ,EffectiveStartDate
                  ,EffectiveEndDate
                  ,ModifiedBy
                  ,ModifiedDateTime)
     ) AS Source
ON Target.SectionId = Source.SectionId
WHEN NOT MATCHED THEN
    INSERT (SectionId
           ,BusinessProcessId
           ,Description
           ,Sequence
           ,EffectiveStartDate
           ,EffectiveEndDate
           ,ModifiedBy
           ,ModifiedDateTime
           )
    VALUES (Source.SectionId
           ,Source.BusinessProcessId
           ,Source.Description
           ,Source.Sequence
           ,Source.EffectiveStartDate
           ,Source.EffectiveEndDate
           ,Source.ModifiedBy
           ,Source.ModifiedDateTime
           );

Simply:

--Arrange

CREATE TABLE dbo.Product
(
    Id   INT IDENTITY PRIMARY KEY,
    Name VARCHAR(40),   
)
GO

--Act

MERGE INTO dbo.Product AS Target 
USING 
(
    --Here is the trick :)

    VALUES 
        (1, N'Product A'),
        (2, N'Product B'),
        (3, N'Product C'),
        (4, N'Product D')
) 
AS 
Source 
(
     Id,
     Name
) 

ON Target.Id= Source.Id

WHEN NOT MATCHED BY TARGET THEN 

INSERT 
(
      Name
) 
VALUES 
(
      Name
);