SQL Update Multiple Fields FROM via a SELECT Statement

Question

This works, but i would like to remove the redundancy. Is there a way to merge the update with a single select statement so i don\'t have to use vars?

    DE         


        

Answer 1

I just had to solve a similar problem where I added a Sequence number (so that items as grouped by a parent ID, have a Sequence that I can order by (and presumably the user can change the sequence number to change the ordering).

In my case, it's insurance for a Patient, and the user gets to set the order they are assigned, so just going by the primary key isn't useful for long-term, but is useful for setting a default.

The problem with all the other solutions is that certain aggregate functions aren't allowed outside of a SELECT

This SELECT gets you the new Sequence number:

select PatientID,
       PatientInsuranceID, 
       Sequence, 
       Row_Number() over(partition by PatientID order by PatientInsuranceID) as RowNum
from PatientInsurance
order by PatientID, PatientInsuranceID

This update command, would be simple, but isn't allowed:

update PatientInsurance
set Sequence = Row_Number() over(partition by PatientID order by PatientInsuranceID)

The solution that worked (I just did it), and is similar to eKek0's solution:

UPDATE PatientInsurance
SET  PatientInsurance.Sequence = q.RowNum
FROM (select PatientInsuranceID, 
             Row_Number() over(partition by PatientID order by PatientInsuranceID) as RowNum
      from PatientInsurance
     ) as q 
WHERE PatientInsurance.PatientInsuranceID=q.PatientInsuranceID 

this lets me select the ID I need to match things up to, and the value I need to set for that ID. Other solutions would have been fine IF I wasn't using Row_Number() which won't work outside of a SELECT.

Given that this is a 1 time operation, it's coding is still simple, and run-speed is fast enough for 4000+ rows