How to set ID value from another table - sql

Question

Let's say I have these tables:
CREATE TABLE [dbo].[Users]
(
[User_ID] [int] IDENTITY(1,1)PRIMARY KEY NOT NULL ,
[LogIn] [varchar](100) NULL,
[Pass] [varchar](100) NOT NULL,
)
CREATE TABLE [dbo].[Consecutives]
(
[Consecutives_ID] [int] IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Name] [varchar](100) NULL,
[Value] [int] NOT NULL,
)
I'm being asked to be able to set an edit the User_ID that is going to be used next when adding a new user using the value stated on the Consecutive table.
So if for example the Consecutive value is 50, even if the last user added has the User_ID set to 8 the new user's ID will be 50 and the consecutive updated to 51.
I would do it using a foreign key, but obviously I can't set a primary key to be a foreign key.
I can't find a way to do this.
Can someone help me out?

Answer 1

What you are describing is called a one-to-one relationship.
You create such a relationship by connecting both tables with a foreign key referencing their primary keys (or a unique index).
However, since this is a one-to-one relationship, only the main table actually needs the identity specification on it's primary key.
Your requirement to insert a record to the Users based on an existing record in the Consecutives table seems strange to me. Usually, when you have a one-to-one relationship you populate the related records in both tables in the same transaction.
To create a one-to-one relationship, where Consecutives is the main table, Your DDL should look like this:
CREATE TABLE [dbo].[Consecutives]
(
[Consecutives_ID] [int] IDENTITY(1,1) NOT NULL,
[Name] [varchar](100) NULL,
[Value] [int] NOT NULL,
CONSTRAINT PK_Consecutives PRIMARY KEY (Consecutives_ID)
);
CREATE TABLE [dbo].[Users]
(
[User_ID] [int] NOT NULL,
[LogIn] [varchar](100) NULL,
[Pass] [varchar](100) NOT NULL,
CONSTRAINT PK_Users PRIMARY KEY (User_ID),
CONSTRAINT FK_Users_Consecutives FOREIGN KEY (User_ID) REFERENCES [dbo].[Consecutives]([Consecutives_ID])
);
Please note I've removed the identity specification from the User_ID column, and also changed the way the primary key is declared so that I could name it manually.
Naming constraints is best practice since if you ever need to change them it's much simpler when you already know their names.
Now, to insert a single record to both tables in the same transaction you can create a stored procedure like this:
CREATE PROCEDURE InsertUser
(
#Name varchar(100),
#Value int,
#LogIn varchar(100),
#Pass varchar(100)
)
AS
DECLARE #Consecutives AS TABLE
(
Id int
);
BEGIN TRY
BEGIN TRANSACTION
INSERT INTO [dbo].[Consecutives] ([Name], [Value])
OUTPUT Inserted.Consecutives_ID INTO #Consecutives
VALUES (#Name, #Value)
INSERT INTO [dbo].[Users] ([User_ID], [LogIn], [Pass])
SELECT Id, #Login, #Pass
FROM #Consecutives
COMMIT TRANSACTION
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0
ROLL BACK TRANSACTION
END CATCH
GO
and execute it like this:
EXEC InsertUser 'Zohar Peled', 1, 'Zohar', 'Peled'
You can see a live demo on rextester. (Please note that rextester doesn't allow using transactions so the try...catch and transaction parts are removed from the demo there)

Answer 2

Have you ever tried set identity insert on? This link may help you. To use the identity insert, the user needs some alter table permissions.