Help me with returing multiple rows - Query

Question

I am trying to return multiple rows and i need help with my query.
and most important of all one of the requirement is the following:
SERVICE LEVEL has categories Sergeant, Bonus I, All Deputies, Deputy Bailiff, Deputy Lockup, Deputy Bailiff Security, Custody Assistant,
Security Officer, Security Assistant, Security Officer and Security Assistant, Private Security, ALL, All Sworn)
Note: Service Level “All Deputies” includes Deputy Bailiff, Deputy Bailiff Security and Deputy Lockup
*“All Sworn”: includes Sergeant, Bonus I, All Deputies, Deputy Bailiff, Deputy Lockup, Deputy Bailiff Security*
//this code doesn't work cuz  case- when statement return only one row. but it works for singles such as 'Sergeant'
select *
from in_service
where rank IN (CASE TRIM(UPPER(:SL))
                WHEN 'ALL DEPUTIES' THEN
                  (SELECT DISTINCT RANK FROM IN_SERVICE
                   WHERE UPPER(RANK) LIKE 'DEPUTY%')
                WHEN 'ALL SWORN' THEN
               (SELECT DISTINCT RANK FROM IN_SERVICE
               WHERE UPPER(RANK) LIKE 'DEPUTY%' OR
               UPPER(RANK) = 'SERGEANT' OR
               UPPER(RANK) = 'BONUS 1')
                WHEN 'ALL' THEN
               (SELECT DISTINCT RANK FROM IN_SERVICE
               WHERE UPPER(RANK) LIKE 'DEPUTY%' OR
               UPPER(RANK) = 'SERGEANT' OR
                UPPER(RANK) = 'BONUS 1' OR
               UPPER(RANK) LIKE 'SECURITY%' OR
               UPPER(RANK) = 'CUSTODY ASSISTANT' OR
                UPPER(RANK) = 'PRIVATE SECURITY') 
                end )   I was able to get multiple rows for 'ALL' and specified category like 'Sergeant' or 'Bonus I' from the code below, but NOT for 'All Deputies' for example which includes Deputy Bailiff, Deputy Bailiff Security and Deputy Lockup. I know CASE, WHEN does NOT return multiple rows, but i am having problems writing the query to make it work for all categories as the requirements mentioned above.
WHERE RANK IN (SELECT RANK FROM (SELECT RANK, 'ALL' ALL_SERVICE
                                        FROM IN_SERVICE
                                        UNION ALL
                                        SELECT RANK, RANK
                                        FROM IN_SERVICE) WHERE ALL_SERVICE = :SL)Please help.
Thanks in advance

Answer 1

If you define your service_level as a table then it will be much easier.
with service_level
as
select 'ALL' parent_lvl, 'Sergeant' srv_lvl from dual union all
select 'ALL', 'Bonus I' from dual union all
select 'ALL', 'Deputy Bailiff' from dual union all
select 'ALL', 'Deputy Lockup' from dual union all
select 'ALL', 'Deputy Bailiff Security' from dual union all
select 'ALL', 'Custody Assistant' from dual union all
select 'ALL', 'Security Officer' from dual union all
select 'ALL', 'Security Assistant' from dual union all
select 'ALL', 'Security Officer and Security Assistant' from dual union all
select 'ALL', 'Private Security' from dual union all
select 'All Deputies', 'Deputy Bailiff' srv_lvl from dual union all
select 'All Deputies', 'Deputy Bailiff Security' from dual union all
select 'All Deputies', 'Deputy Lockup' from dual union all
select 'All Sworn', 'Sergeant' srv_lvl from dual union all
select 'All Sworn','Bonus I' from dual union all
select 'All Sworn','All Deputies' from dual union all
select 'All Sworn','Deputy Bailiff' from dual union all
select 'All Sworn','Deputy Lockup' from dual union all
select 'All Sworn','Deputy Bailiff Security' from dual
select *
  from in_service
where rank IN (
          select srv_lvl
            from service_level
           where upper(parent_lvl) = upper(:SL)
              or upper(srv_lvl) = upper(:SL)
               )