Joining onto a table that doesn't have ranges, but requires ranges - sql

Question

Trying to find the best way to write this SQL statement.
I have a customer table that has the internal credit score of that customer. Then i have another table with definitions of that credit score. I would like to join these tables together, but the second table doesn't have any way to link it easily.
The score of the customer is an integer between 1-999, and the definition table has these columns:
Score
Description
And these rows:
60 LOW
99 MED
999 HIGH
So basically if a customer has a score between 1 and 60 they are low, 61-99 they are med, and 100-999 they are high.
I can't really INNER JOIN these, because it would only join them IF the score was 60, 99, or 999, and that would exclude anyone else with those scores.
I don't want to do a case statement with the static numbers, because our scores may change in the future and I don't want to have to update my initial query when/if they do. I also cannot create any tables or functions to do this- I need to create a SQL statement to do it for me.
EDIT:
A coworker said this would work, but its a little crazy. I'm thinking there has to be a better way:
SELECT
internal_credit_score
(
SELECT
credit_score_short_desc
FROM
cf_internal_credit_score
WHERE
internal_credit_score = (
SELECT
max(credit.internal_credit_score)
FROM
cf_internal_credit_score credit
WHERE
cs.internal_credit_score <= credit.internal_credit_score
AND credit.internal_credit_score <= (
SELECT
min(credit2.internal_credit_score)
FROM
cf_internal_credit_score credit2
WHERE
cs.internal_credit_score <= credit2.internal_credit_score
)
)
)
FROM
customer_statements cs

Answer 1

try this, change your table to contain the range of the scores:
ScoreTable
-------------
LowScore int
HighScore int
ScoreDescription string
data values
LowScore HighScore ScoreDescription
-------- --------- ----------------
1 60 Low
61 99 Med
100 999 High
query:
Select
.... , Score.ScoreDescription
FROM YourTable
INNER JOIN Score ON YourTable.Score>=Score.LowScore
AND YourTable.Score<=Score.HighScore
WHERE ...

Answer 2

Assuming you table is named CreditTable, this is what you want:
select * from
(
select Description, Score
from CreditTable
where Score > 80 /*client's credit*/
order by Score
)
where rownum = 1
Also, make sure your high score reference value is 1000, even though client's highest score possible is 999.
Update
The above SQL gives you the credit record for a given value. If you want to join with, say, Clients table, you'd do something like this:
select
c.Name,
c.Score,
(select Description from
(select Description from CreditTable where Score > c.Score order by Score)
where rownum = 1)
from clients c
I know this is a sub-select that executed for each returning row, but then again, CreditTable is ridiculously small and there will be no significant performance loss because of the the sub-select usage.

Answer 3

You can use analytic functions to convert the data in your score description table to ranges (I assume that you meant that 100-999 should map to 'HIGH', not 99-999).
SQL> ed
Wrote file afiedt.buf
1 with x as (
2 select 60 score, 'Low' description from dual union all
3 select 99, 'Med' from dual union all
4 select 999, 'High' from dual
5 )
6 select description,
7 nvl(lag(score) over (order by score),0) + 1 low_range,
8 score high_range
9* from x
SQL> /
DESC LOW_RANGE HIGH_RANGE
---- ---------- ----------
Low 1 60
Med 61 99
High 100 999
You can then join this to your CUSTOMER table with something like
SELECT c.*,
sd.*
FROM customer c,
(select description,
nvl(lag(score) over (order by score),0) + 1 low_range,
score high_range
from score_description) sd
WHERE c.credit_score BETWEEN sd.low_range AND sd.high_range