Question

Is there a way to update a column only when it is null and leave it as it is when it is not null in one multiple-columns-update query?
something like below. (like how we use case in select statements)

UPDATE users  SET users.city = 'Dallas',
      CASE
          WHEN users.Global_id IS NULL
          THEN
              users.Global_id = '123'
      END WHERE userid = '12312312'

The above update statement throws ORA-00927: missing equal sign error.

Reason why I am looking for this?
I have a schedule job that runs a similar query like above.
And there also exists a trigger in users table that will raise error if you try to update a ‘not null’ global_id. So my job fails when it encounters this trigger.

I have one option… to split this update query to two.. one to update city and one to update global_id where global_id is null.

But wondering if this can be achieved by any other way… Any idea would be appreciated.

Answer 1

You can use coalesce function:

UPDATE users  
SET 
   users.city = 'Dallas',
   users.Global_id = coalesce( users.Global_id, '123')

Also, you can split your update in two sentences, remember than you can enclose it in a single transaction:

UPDATE users  
SET 
   users.city = 'Dallas';

UPDATE users  
SET 
   users.Global_id = '123'
WHERE
    users.Global_id is null