Adding a new column that auto increments based on existing field values - sql

Question

Not sure how to do this, but I want to add a new column "Jersey" that will increment by 1 depending on the "Sport" value in both tab_A and tab_B. So if a "Sport" already exists in tab_B, then just grab the max jersey_no and add 1 for the new column. That one is easy.
Now if the "Sport" does not exist in tab_B, then give it a "Jersey" value of 100 for the new column. However, if there is more than one of the same "Sport" in tab_A (but do not exist in tab_B), then it should start with 100 and increment by 1 for the next same Sport, and so on (e.g. see Garcia example below).
I created a sequence "seqnce" but, that really didn't help at all. Is there another way to accomplish this? Thanks in advance!
Tab_A
Name State Sport
Garcia CA Basketball
Garcia AL Basketball
Garcia NY Basketball
McGee CA Swimming
Tontou CA Football
Tontou AL Swimming
Tab_B
Name Sport Jersey_No
Garcia Swimming 100
Garcia Football 100
McGee Swimming 101
Tontou Swimming 101
Tontou Swimming 102
Expected Output
Name State Sport Jersey
Garcia CA Basketball 100
Garcia AL Basketball 101
Garcia NY Basketball 102
McGee CA Swimming 102
Tontou CA Football 100
Tontou AL Swimming 103
My Code
select name, state, sport
,nvl ((select max(b.jersey_no + 1) from tab_b b
where b.sport = a.sport
and b.name = a.name),
(case
when not exists (select 1 from tab_b b
where b.sport = a.sport
and b.name = a.name
having count(a.sport) > 1)
then seqnce.nextval
else '100'
end )
) Jersey
from tab_a

Answer 1

If it's only select result then using row_number(). If you need update column in table, then write trigger
Example this:
WITH taba AS
(SELECT 'Garcia' Name, 'CA' State, 'Basketball' Sport from dual
UNION ALL
SELECT 'Garcia' Name, 'AL' State, 'Basketball' Sport from dual
UNION ALL
SELECT 'Garcia' Name, 'NY' State, 'Basketball' Sport from dual
UNION ALL
SELECT 'McGee' Name, 'CA' State, 'Swimming' Sport from dual
UNION ALL
SELECT 'Tontou' Name, 'CA' State, 'Football' Sport from dual
UNION ALL
SELECT 'Tontou' Name, 'AL' State, 'Swimming' Sport from dual),
tabb AS
(SELECT 'Garcia' Name, 'Swimming' Sport, 100 Jersey from dual
UNION ALL
SELECT 'Garcia' Name, 'Football', 100 from dual
UNION ALL
SELECT 'McGee' Name, 'Swimming', 101 from dual
UNION ALL
SELECT 'Tontou' Name, 'Swimming', 101 from dual
UNION ALL
SELECT 'Tontou' Name, 'Swimming', 102 from dual)
SELECT taba.Name,
taba.State ,
taba.Sport,
row_number() over(partition by taba.Name, taba.Sport ORDER BY taba.State)
+ nvl((SELECT MAX(tabb.Jersey)
FROM tabb
WHERE taba.name = tabb.name
AND taba.sport = tabb.sport), 99)
FROM taba
result:
Garcia AL Basketball 100
Garcia CA Basketball 101
Garcia NY Basketball 102
McGee CA Swimming 102
Tontou CA Football 100
Tontou AL Swimming 103