Case statement logic and substring - sql

Question

Say I have the following data:
Passes
ID | Pass_code
-----------------
100 | 2xBronze
101 | 1xGold
102 | 1xSilver
103 | 2xSteel
Passengers
ID | Passengers
-----------------
100 | 2
101 | 5
102 | 1
103 | 3
I want to count then create a ticket in the output of:
ID 100 | 2 pass (bronze)
ID 101 | 5 pass (because it is gold, we count all passengers)
ID 102 | 1 pass (silver)
ID 103 | 2 pass (steel)
I was thinking something like the code below however, I am unsure how to finish my case statement. I want to substring pass_code so that we get show pass numbers e.g '2xBronze' should give me 2. Then for ID 103, we have 2 passes and 3 customers so we should output 2.
Also, is there a way to firstly find '2xbronze' if the pass_code contained lots of other things such as '101001, 1xbronze, FirstClass' - this may change so i don't want to substring, could we search for '2xbronze' and then pull out the 2??
SELECT
CASE
WHEN Passes.pass_code like '%gold%' THEN Passengers.passengers
WHEN Passes.pass_code like '%steel%' THEN SUBSTRING(passes.pass_code, 1,1)
WHEN Passes.pass_code like '%bronze%' THEN SUBSTRING(passes.pass_code, 1,1)
WHEN Passes.pass_code like '%silver%' THEN SUBSTRING(passes.pass_code, 1,1)
else 0 end as no,
Passes.ID,
Passes.Pass_code,
Passengers.Passengers
FROM Passes
JOIN Passengers ON Passes.ID = Passengers.ID
https://dbfiddle.uk/?rdbms=oracle_18&fiddle=db698e8562546ae7658270e0ec26ca54

Answer 1

So assuming you are indeed using Oracle (as your DB fiddle implies).
You can do some string magic with finding position of a splitter character (in your case the x), then substringing based on that. Obviously this has it's problems, and x is a bad character seperator as well.. but based on your current set.
WITH PASSCODESPLIT AS
(
SELECT PASSES.ID,
TO_Number(SUBSTR(PASSES.PASS_CODE, 0, (INSTR(PASSES.PASS_CODE, 'x')) - 1)) AS NrOfPasses,
SUBSTR(PASSES.PASS_CODE, (INSTR(PASSES.PASS_CODE, 'x')) + 1) AS PassType
FROM Passes
)
SELECT
PASSCODESPLIT.ID,
CASE
WHEN PASSCODESPLIT.PassType = 'gold' THEN Passengers.Passengers
ELSE PASSCODESPLIT.NrOfPasses
END AS NrOfPasses,
PASSCODESPLIT.PassType,
Passengers.Passengers
FROM PASSCODESPLIT
INNER JOIN Passengers ON PASSCODESPLIT.ID = Passengers.ID
ORDER BY PASSCODESPLIT.ID ASC
Gives the result of:
ID NROFPASSES PASSTYPE PASSENGERS
100 2 bronze 2
101 5 gold 5
102 1 silver 1
103 2 steel 3
As can also be seen in this fiddle
But I would strongly advise you to fix your table design. Having multiple attributes in the same column leads to troubles like these. And the more variables/variations you start storing, the more 'magic' you need to keep doing.
In this particular example i see no reason why you don't simply have the 3 columns in Passes, also giving you the opportunity to add new columns going forward. I.e. to keep track of First class.

Answer 2

You can extract the numbers using regexp_substr(). So I think this does what you want:
SELECT (CASE WHEN p.pass_code LIKE '%gold%'
THEN TO_NUMBER(REGEXP_SUBSTR(p.pass_code, '^[0-9]+'))
ELSE pp.passengers
END) as num,
p.ID, p.Pass_code, pp.Passengers
FROM Passes p JOIN
Passengers pp
ON p.ID = pp.ID;
Here is a db<>fiddle.
This converts the leading digits in the code to a number. Also note the use of table aliases to simplify the query.