Case expression many cases

Question

Hi all,
I am creating a Java application that - among other useful things - needs to change the values of the DB according a to a huge (maybe > 1000 mappings) , user-created (through the UI) mapping like the one below:
DB Value  UI Value
a --> A1
b --> B2
c --> C3
d --> D4
e --> E5
f --> F6
So, if my SELECT contains the column that needs its values changed (the values on the left), I need to somehow get the values on the right.
Normally, I would create a table with this mapping and use it in my query to have it return the values I need. However, I cannot do this, because I don't have (and will not get) privileges to create tables or procedures.
* One solution that comes into my mind is to generate through Java a query with a HUGE case expression, with a case for each mapping. But this does not seem right.
* Another thing I could do is make the query return the DB value and in my application I could do this mapping.
Is there a more elegant way to do the mapping without creating a table in the DB?
Thanks,
Markos
Edited by: user622271 on Jun 23, 2009 6:42 AM

Answer 1

Your best bet is a lookup table. If you do not have privilege to create a lookup table for some reason, then you should be allowed to create a view.
I am not sure how many mappings you will finally have, but it sounds like too much to DECODE. But in a simpler circumstance, you could use DECODE directly in your application SQL or use it to create a view then access the view from your application instead of the table.
SELECT DECODE(db_value,
              'a','A1',
              'b','B2',
              'c','C3',
              'd','D4',
              'x','Xn') ui_value
FROM table_name
/If you are lucky to have your db_value exist with some kind of pattern, then you can reduce the number of lines with some pattern matching.