Question

Considering the following tables:

Users
----------------------
Id  | 1   | 2
Name| John| Jack

Cars
----------------------
Id  | 14      | 26
Name| Mercedes| BMW

Import
-----------------------
Id         | 12   | 34
UserName   | John | Daniel
UserId     | NULL | NULL
CarName    | BMW  | Mercedes
CarId      | NULL | NULL
SomeOtherId| 45   | 45

I basically want to find UserId and CarId in the other tables, If they are not find they remain NULL,

I tried something like

UPDATE Import i
SET UserId = ( SELECT Id FROM Users WHERE Name=i.UserName ),
    CarId = ( SELECT Id FROM Cars WHERE Name= i.CarName )
WHERE SomeOtherId=45;

In this case i am getting an incorrect syntax.
How can i fix it?
Is it a way to use MERGE in this case? (merging more than 2 tables and using a WHERE clause)?
Thanks.

Answer 1

You might use from clause in update itself:

UPDATE i
   SET UserId = Users.Id,
       CarId = Cars.Id
  FROM Import i
  LEFT JOIN Users
    ON i.UserName = Users.Name
  LEFT JOIN Cars
    ON i.CarName = Cars.Name
 WHERE i.SomeOtherId=45;