Query join help

Question

Hello everyone, I kindly need help with a query I am trying to write. I think it's meant to be a kind of join but I'm a little unsure. Here is an example:
select a.person_id, a.company, b.name, e.element, f.value
from a, b, e, f
where a.person_id = b.person_id
and e.el_id = f.el_id
-- e.t.c
Lets say this returns
person_id, company, name, element, value
1, Vols, krog, lunch, 34
2, Mols, flog, munch, 24
The problem now is the table e. I want to get all values from table e that meet a certain criteria. As in:
select e.element
where e.name = 'EVALUE'
Lets say this returns
element
food
lunch
munch
And combine it with the top query. But I also want to show all of the other values, a.person_id, a.company, b.name for each row.
So my goal is to have finally:
person_id, company, name, element, value
1, Vols, krog, lunch, 34
1, Vols, krog, food, 0
1, Vols, krog, munch, 0
2, Mols, flog, munch, 24
2, Mols, flog, food, 0
2, Mols, flog, lunch, 0
That is to have a default for zero where no join exists for value and not to duplicate anything although I could still use distinct.
Can anyone help with this?

Answer 1

with t1 as (
            select a.person_id, a.company, b.name, e.element, f.value
              from a, b, e, f
              where a.person_id = b.person_id
              and e.el_id = f.el_id
              -- e.t.c
     t2 as (
            select e.element
             where e.name = 'EVALUE'
select  person_id,
        company,
        name,
        t2.element,
        sum(
            case t1.element
              when t2.element then value
              else 0
            end
           ) value
  from  t1,
        t2
  group by person_id,
           company,
           name,
  order by person_id,
           company,
           name,
           t2.element
/For example:
with t1 as (
            select 1 person_id, 'Vols' company, 'krog' name, 'lunch' element, 34 value from dual union all
            select 2, 'Mols', 'flog', 'munch', 24 from dual
     t2 as (
            select 'food' element from dual union all
            select 'lunch' from dual union all
            select 'munch' from dual
select  person_id,
        company,
        name,
        t2.element,
        sum(
            case t1.element
              when t2.element then value
              else 0
            end
           ) value
  from  t1,
        t2
  group by person_id,
           company,
           name,
           t2.element
  order by person_id,
           company,
           name,
           t2.element
PERSON_ID COMP NAME ELEME      VALUE
         1 Vols krog food           0
         1 Vols krog lunch         34
         1 Vols krog munch          0
         2 Mols flog food           0
         2 Mols flog lunch          0
         2 Mols flog munch         24
6 rows selected.
SQL> SY.