Trying to get a record count

Question

select count(*)
from dist_ln a
left outer join jrnl_ln b on
a.journal_id = b.journal_id and
a.journal_line = b.journal_line and
a.journal_date = b.journal_date
where a.DISTRIB_STATUS = 'D'
and b.journal_id is null
and a.business_unit = '00001'
This select never completes. It does for other business units. The problem is there are 20X more rows for this BU 00001 in the dist_ln table.
There are a little over 900000 rows in the dist_ln table with BU of 00001.

Answer 1

First, aliases like "a" and "b" make even a simple query like this harder to read.
select count(*)
  from dist_ln dl
       left outer join jrnl_ln jl on
         jl.journal_id = dl.journal_id and
         jl.journal_line = dl.journal_line and
         jl.journal_date = dl.journal_date
where dl.DISTRIB_STATUS = 'D'
   and jl.journal_id is null
   and dl.business_unit = '00001';Then, the combination of a left outer join and an "is null" requirement on one of the join columns is equivalent to specifying that the table to which you are joining has no matching rows. So consider the following options:
select count(*)
  from dist_ln dl
where dl.DISTRIB_STATUS = 'D'
   and dl.business_unit = '00001'
   and not exists (
       select 'x'
         from jrnl_ln  jl
        where  jl.journal_id = dl.journal_id
         and jl.journal_line = dl.journal_line
         and jl.journal_date = dl.journal_date );
select count(*)
  from (
select journal_id,
       journal_line,
       journal_date
  from dist_ln dl
where dl.DISTRIB_STATUS = 'D'
   and dl.business_unit = '00001'
minus
select journal_id,
       journal_line,
       journal_date
  from jrnl_ln  jl
       );