Question

What is the simplest way to insert a Car for each user in Users and set the users CarID to the ID of the inserted Car?

[Users]

- ID
- Name
- CarID

[Cars]

- ID (Auto increment)
- Name

Sorry if this might be a duplicate question but I can’t find any simple solutions. Everything I’ve found is using complicated cursors, pointers etc.

A simple and reusable syntax for this would save me hours while migrating data during system upgrades etc.

Answer 1

If you are on SQL Server 2008 or later you can use merge and output something like this.

Sample tables and data:

declare @Users table
(
  ID int identity primary key,
  Name varchar(10) not null,
  CarID int null
);

declare @Cars table
(
  ID int identity primary key,
  Name varchar(10) not null
);

insert into @Users(Name) values ('User1'),('User2'),('User3');

Add one care for each user and move the auto-generated CarID back to Users.

declare @ID table(CarID int, UserID int)

merge @Cars as C
using @Users as U
on 0 = 1
when not matched then
  insert (Name) values ('CarName')
output inserted.ID, U.ID into @ID;

update U
set CarID = I.CarID
from @Users as U
  inner join @ID as I
    on U.ID = I.UserID 

Try it out on SE Data.

More info on the merge/output trick can be found here.