在 SQL Server 2008 R2 中，有没有办法在不使用 IDENTITY(1,1) 的情况下创建自定义自动增量标识字段？

Question

I would like to be able to pull the custom key value from a table, but would also like it to perform like SQL Server's IDENTITY(1,1) column on inserts.

The custom key is for another application and will need to be used by different functions so the value will need to be pulled from a table and available for other areas.

Here are some if my attempts:

1. Tried a trigger on the table works well on single inserts, failed on using SQL insert (forgetting the fact that a triggers are not per row but by batch)

ALTER TRIGGER [sales].[trg_NextInvoiceDocNo] 
ON [sales].[Invoice]
AFTER INSERT 
AS
BEGIN
    DECLARE @ResultVar VARCHAR(25)
    DECLARE @Key VARCHAR(25)

    EXEC [dbo].[usp_GetNextKeyCounterChar] 
               @tcForTbl = 'docNbr', @tcForGrp = 'docNbr', @NewKey =      @ResultVar OUTPUT

    UPDATE sales.InvoiceRET
    SET DocNbr = @ResultVar
    FROM sales.InvoiceRET
    JOIN inserted ON inserted.id = sales.InvoiceRET.id;
END;

2. Thought about a scalar function, but functions cannot exec stored procedures or update statements in order to set the new key value in the lookup table.

Thanks

Answer 1

You can use ROW_NUMBER() depending on the type of concurrency you are dealing with. Here is some sample data and a demo you can run locally.

-- Sample table
USE tempdb
GO
IF OBJECT_ID('dbo.sometable','U') IS NOT NULL DROP TABLE dbo.sometable;
GO
CREATE TABLE dbo.sometable
(
  SomeId INT NULL,
  Col1   INT NOT NULL
);
GO

-- Stored Proc to insert data
CREATE PROC dbo.InsertProc @output BIT AS
BEGIN -- Your proc starts here
  INSERT dbo.sometable(Col1) 
  SELECT datasource.[value]
  FROM   (VALUES(CHECKSUM(NEWID())%100)) AS datasource([value]) -- simulating data from somewhere
  CROSS APPLY (VALUES(1),(1),(1)) AS x(x);

  WITH 
  id(MaxId) AS (SELECT ISNULL(MAX(t.SomeId),0) FROM dbo.sometable AS t),
  xx AS 
  (
    SELECT     s.SomeId, RN = ROW_NUMBER() OVER (ORDER BY (SELECT NULL))+id.MaxId, s.Col1, id.MaxId
    FROM       id     AS id
    CROSS JOIN dbo.sometable AS s
    WHERE      s.SomeId IS NULL
  )
  UPDATE xx SET xx.SomeId = xx.RN;

  IF @output = 1
  SELECT t.* FROM dbo.sometable AS t;
END
GO 

Each time I run: EXEC dbo.InsertProc 1; it returns 3 more rows with the correct ID col. Each time I execute it, it adds more rows and auto-increments as needed.

SomeId   Col1
-------- ------
1        62
2        73
3        -17