Question

I have 3 queries which retrieves maximum value depending on a condition.

select max(to_number(substr(attr_value,9)))+1 
  from circ_inst inner
  join circ_attr_settings 
    on circ_inst.circ_inst_id=circ_attr_settings.circ_inst_id 
   and val_attr_inst_id=1045 
 where circ_attr_settings.attr_value like 'IPANEMA-%' 



select max(to_number(substr(attr_value,10)))+1 
  from circ_inst inner
  join circ_attr_settings 
    on circ_inst.circ_inst_id=circ_attr_settings.circ_inst_id 
   and val_attr_inst_id=1045 
 where circ_attr_settings.attr_value like 'FIREWALL-%'



select max(to_number(substr(attr_value,16)))+1 
  from circ_inst 
 inner join circ_attr_settings
    on circ_inst.circ_inst_id=circ_attr_settings.circ_inst_id
   and val_attr_inst_id=1045 
 where circ_attr_settings.attr_value like 'LAYER2 SWITCH-%'

I would like to get the maximum number out of these 3 queries(if the results of the 3 queries are 6430, 6434 and 6418 respectively, then I would like to get the value “6434” which is the maximum of the three results.

I tried using max(query1,query2,query3) but not successful.

Answer 1

I think you can do this with one query:

select max(to_number(substr(attr_value,instr(attr_value, '-')+1)))+1
from circ_inst inner join
     circ_attr_settings
     on circ_inst.circ_inst_id=circ_attr_settings.circ_inst_id and
        val_attr_inst_id=1045
where circ_attr_settings.attr_value like 'LAYER 2 SWITCH-%') or
      circ_attr_settings.attr_value like 'IPANEMA-%' or
      circ_attr_settings.attr_value like 'FIREWALL-%'

Your joins all appear to be the same. The only difference is extracting the number. You can get the right start location by looking for a “-” in the value.