Please Help | Dyanamic variable based on another field

Question

In the query below, I'm attempting to replace task codes with task descriptions by left joining to a multi-purpose control table.
In our corp, the description for the task code varies based on the value of change_program in each record, so rather than referencing the value of code_index.tabl statically as I do in the query below (201), I need a dyanamic variable to be defined for each record based on the value of work.change_program, which would represent the value for code_index.tabl.
     For each record
          if change_program =1 then v_tabl = 201
          elseif change_program =2 then v_tabl = 202
          elseif change_program =3 then v_tabl = 203
          else v_tabl = 201
BTW, I'm really a noob, so I have no idea how to declare and use variables, but I'm sure it must be possible. Any assistance with the syntax would be GREATLY appreciated.
SELECT account,
change_program,
task_code_01,
task_code_02,
task1.longdesc,
task2.longdesc
FROM work
left join (SELECT id,
longdesc
FROM code_index
WHERE corp = mem
AND tabl = 201) task1
ON task1.id = work.task_code_01
left join (SELECT id,
longdesc
FROM code_index
WHERE corp = mem
AND tabl = 201) task2
ON task2.id = work.task_code_02
WHERE work.corp = mem

Answer 1

Welcome to the forum,
CASE WHEN change_program =1 THEN  201
   WHEN change_program =2 THEN   202
   WHEN change_program =3 THEN   203
   ELSE  201
ENDis a valid construct in SELECT statement.
Check SELECT syntax in ORacle documentation.
vr
Sudhakar B.