How can I have two columns in SQL Server auto increment?

问题

I have two columns in a table of a SQL server DB that I would like to autoincrement when new fields are added. However, Managment Studio wont allow me to set two columns to IDENTITY. Is there some other way to do this?

回答1:

You could make the second field a calculated field based on the first.

Or make an INSERT trigger than programatically generates the value for the second.

回答2:

If you wanted the 2nd column to basically be a mirror of the first:

ALTER TABLE dbo.myTable ADD
   foo  AS [rowid]
GO

If you wanted it to apply some math formula to it to achieve some kind of offset:

ALTER TABLE dbo.myTable ADD
    foo  AS ([rowid]+1) * 7 --or whatever you like.
GO

回答3:

There can only be one auto increment field per table. But, you could have a calculated field based on the auto increment field. Or, you could have an int field where you manage the sequence by front end code or by a trigger. And also you could use a sequence in SQL Server.

CREATE SEQUENCE MySequence START WITH 100;

CREATE TABLE MyTable
(
    RealIdentity INT IDENTITY(1,1),
    RandomCol NVARCHAR(100),
    FakeIdentity INT DEFAULT NEXT VALUE FOR MySequence
);

来源：https://stackoverflow.com/questions/3622627/how-can-i-have-two-columns-in-sql-server-auto-increment