Report based on mutually exclusive items:

Question

Hi guys,
I am trying to create a parameterized report based on mutually exclusive items:
I have a Select List item "P1_Property_type" which has these values ( office , apartment ),
if 'office' is chosen then the report should consider ONLY the value of the select list item "P1_beds"
if 'apartment' is chosen then the report should consider ONLY the value of the select list "P1_size"
I used this query, but it does not seem to wrok:
select * from realestate where
unit_type = decode (:P1_PROPERTY_TYPE,'null',unit_type,:P1_property_type)
and
( br= decode (:P1_beds,'null',br,:P1_beds) or size= decode (:P1_size,'null',size,:P1_size) )----------------
I hope my question is clear
Regards,
Fateh

Answer 1

Assuming you're using the string literal 'null' rather than NULL.
"it does not seem to work" because of this:
( br= decode (:P1_beds,'null',br,:P1_beds) or size= decode (:P1_size,'null',size,:P1_size) )Assuming you pick "office" and :p1_beds is set and :p1_size is 'null', you end up with a statement that is the equivalent of:
select * from realesate
where unit_type = 'office'
and (br = :p1_beds
or size=size)    <--------------problemand your :p1_beds restriction is then ineffective.
I'm not a fan of decode to do this logic.
I prefer a clear statement of exclusive predicates which the optimizer can sometimes deal with more effectively.
e.g. assuming that it's irrelevant whether you pick office or appartment because the relevant parameter :p1_beds or :p1_size will be set appropriately:
select * from realestate
where
      (:p1.property_type is null / = 'null'
or    (:p1.property_type is not null / != 'null'
and    unit_type          = :p1_property_type))
and   (:p1_beds          is null / = 'null'
or    (:p1_beds          is not null / != 'null'
and    br                 = :p1_beds))
and   (:p1_size          is null / = 'null'
or    (:p1_size          is not null / != 'null'
and    size               = :p1_size))Note that I've provided alternatives depending on whether you're actually using NULL or a magic string.