Update with Incrementing column - sql

Question

Example table:
Sample
------
id (primary key)
secondaryId (optional secondary key)
crtdate (created date)
... (other fields)
Some users use secondaryId for identifying rows (i.e., should be unique)
When the rows were created, secondaryId did not get a value, and was defaulted to 0.
Subsequently, rows were given a secondaryId value as they were used.
I need to update all rows with value 0 to be the next available number.
Desired result (w/ simplified values):
From: To:
id secondaryId id secondaryId
1 0 1 7 // this is the max(secondaryId)+1
2 0 2 8 // incrementing as we fill in the zeroes
3 5 3 5 // already assigned
4 0 4 9 // keep incrementing...
5 6 5 6 // already assigned
This query would accomplish what I want to do; but alas, CTE + UPDATE is not supported:
with temp(primary, rownumber) as (
values (
select
id,
row_number() over (partition by secondaryId order by crtdate)+6 --6 is max secondaryId
from Sample
where secondaryId='0'
)
update Sample set secondaryId=temp.rownumber where Sample.id=temp.id
Does anyone have suggestions for a different way to approach this problem? I'm now suffering from tunnel vision...

Answer 1

You can use MERGE statement as id is primary key and there won't be any duplicates.
MERGE INTO Sample as trgt
Using (
select id,
row_number() over (partition by secondaryId order by crtdate)+6 secondaryId
--6 is max secondaryId
from Sample where secondaryId='0'
) as src
ON( src.id= trgt.id)
WHEN MATCHED THEN UPDATE SET trgt.secondaryid = src.secondaryId

Answer 2

You can also UPDATE a SELECT (well "fullselect"), which is probably the neatest solution here
create table sample (
id int not null primary key
, secondaryId int not null
, crtdate date not null
)
;
INSERT INTO sample VALUES
( 1 , 0 , current_date)
,( 2 , 0 , current_date)
,( 3 , 5 , current_date)
,( 4 , 0 , current_date)
,( 5 , 6 , current_date)
;
UPDATE (
SELECT id, secondaryId
, ROW_NUMBER() OVER(ORDER BY secondaryId Desc)
+ (SELECT MAX(id) from sample) as new_secondaryId
FROM
sample s
WHERE secondaryId = 0
)
SET secondaryId = new_secondaryId
;
https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.1.0/com.ibm.db2.luw.sql.ref.doc/doc/r0001022.html

Answer 3

For a Template method (not necessary to know max value), you can try this:
create table tmptable as (
select f1.id, row_number() over(order by f1.crtdate) + ifnull((select max(f2.secondaryId) from Sample f2), 0) newsecondary
from Sample f1 where f1.secondaryId='0'
) with data;
update Sample f1
set f1.secondaryId=(
select f2.newsecondary
from tmptable f2
where f2.id=f1.id
)
where exists
(
select * from tmptable f2
where f2.id=f1.id
);
drop table tmptable;