Select max value from a table and increment it in another - sql

Question

I'm struggling with a sql query, and will appreciate any help.
I have two tables, they both have a sort column. The first one looks like this:
person_id
image_name
sort_number
739
chest.png
1
739
legs.png
2
And the second table like this
person_id
advert
sort_number
739
house.png
1
739
car.png
2
I want to be able to select the max sort_number from the table1 and make the first sort_number in table2 (house.png) to become 3, and the sort_number for car.png) to become 4.
Essentially, what I'm looking to achieve is an insert statement that selects from table2 and insert into table1, but I need the sort_number not to have duplicate, so the starting sort_number from the table2 should be the max of table1+1...and so on. If table1 does not have the person, I simply insert and not change the sort_number value.
I would appreciate of someone can help me please.

Answer 1

Here's one way:
With grouped as
(Select person_id, max(sort_num) as maxsort
From table1
Group by person_id)
Select t2.person_id, t2.advert, t2.sort_num + coalesce(g.maxsort,0) as newsortnum
From table t2
Left join grouped g on t2.person_id = g.person_id
This will get max value of sort number for each key in the first table, and then attempt to join the second table to this grouped dataset. If there is a match, you add your second table's value to the max, and retain the value from the second table otherwise.

Answer 2

You could try using UNION ALL and ROW_NUMBER:
WITH CTE AS
(
SELECT
person_id,
image_name,
sort_number,
1 sort_table
FROM dbo.Table1 t1
UNION ALL
SELECT
person_id,
advert,
sort_number,
2
FROM dbo.Table2 t2
)
SELECT
person_id,
image_name,
ROW_NUMBER() OVER(PARTITION BY person_id ORDER BY sort_table, sort_number) sort_number
FROM CTE
;

Answer 3

insert into table2(person_id, advert, sort_number)
select table1.person_id, table1.image_name, table1.sort_number + table2.sort_number
from table1
join table2
on 1 = 1
left join table2 newer
on table2.sort_number < newer.sort_number
left join table1 mismatch
on table2.person_id = mistmatch.person_id and table2.advert = mismatch.image_name
where newer.person_id is null and mismatch.person_id is null
Firs join: we need to pair table1 and table2
Second join: we make sure that table2 record in the pair is the newest
Third join: we make sure that we do not insert what's already there.