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Asked: 2026-05-17T14:55:38+00:00

I have another simple one. How to make a long decode inside a function

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I have another simple one. How to make a long decode inside a function in oracle?

My select looks like this:

select something, sum(ofsomethingelse)
from a_table
where code in 
('390','391','392','393','394','395','396','397','398','400','402','406',
'407','408','409','410','411','412','413','414','416','418','471','473',
'1734','1742','1735','1736','1737','1738','1739','1740','1741','1745',
'1748','1752','1760','1753','1754','1755','1756','1757','1758','1759',
'1763','1766','1902','1904','1003','1011','1004','1005','106','1007',
'1008','1009','1010','1159','1161','1015','1023','1016','1017','1018',
'1019','1020','1021','1022','1164','1166','1189','1191','1201','1209',
'1202','1203','1204','205','1206','1207','1208','1356','1358','1213',
'1221','1214','1215','1216','1217','1218','1219','1220','1361','1363',
'1386','1388','1401','1409','1402','1403','1404','1405','1406','1407',
'1408','1557','1559','1413','1421','1414','1415','1416','1417','1418',
'1419','1420','1562','1564','1587','1589','9033','9034','9035','9036',
'9037','9038','909','9040','9049','9050','9051','9052')
group by something
order by 1

And I have a couple more of large code lists like that which I want to turn into one neat query.

Something like:

CREATE OR REPLACE FUNCTION grouping_func (id_in IN varchar2)
RETURN varchar2
AS
res varchar(255);
BEGIN
   res := CASE id_in
            WHEN id_in in ([long list of ids from query1]) THEN 'Group1'
            WHEN id_in in ([long list of ids from query2]) THEN 'Group2'
            WHEN id_in in ([long list of ids from query3]) THEN 'Group3'
            ELSE id_in
          END;
    RETURN res;
END;

so I can have a clear query that just uses this function into the group by and everything the way I like 🙂

The problem is I cant use that id_in in ([long list of ids from query3]) in the switch cases and I’m quite a n00b in plsql…

May I get suggestions of elegant ways of doing it?

thanks!

f.

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1 Answer

  1. Editorial Team

    Actually, the only problem with your first stab is that you’ve mixed up the two syntaxes of the CASE expression.

    If you follow the CASE keyword with an expression (e.g. id_in), then you are doing a switch on the value of that expression, and each of the WHEN clauses must include a single expression that will be checked for equality against the first expression.

    Alternatively, you can skip the expression immediately after CASE, and specify a full boolean condition in each WHEN clause.

    So, either of these should work for you:

       res := CASE id_in
         WHEN 390 THEN 'Group1'
         WHEN 391 THEN 'Group1'
         WHEN 392 THEN 'Group2'
         ...etc...

   res := CASE
            WHEN id_in in ([long list of ids from query1]) THEN 'Group1'
            WHEN id_in in ([long list of ids from query2]) THEN 'Group2'
            WHEN id_in in ([long list of ids from query3]) THEN 'Group3'
            ELSE id_in
          END;

    Note that overall, I agree with others that the preferable way to do this is store the mapping of ID values to groups in another table and change the query to a join.

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