Subqueries in 2 tables - oracle

Question

I have 2 tables: machine and work.
Table:machine
machine_no downtime location
A1-100-01 2 A1
A1-100 1.5 A1
A1-200 3 A1
CC3-100-01 0.5 CC3
CC3-100 1.5 CC3
Table:work
machine_no date
A1-100-01 2/4/14
A1-100 2/14/14
A1-200 2/6/14
CC3-100-01 3/15/14
CC3-100 3/2/14
I want the output to be like this:
machine_no total_downtime month
A1-100 3.5 (total of A1-100, A1-100-01) 02
A1-200 3 02
When location A1 is selected.
SELECT machine_no, SUM(downtime) as total_downtime
FROM (
SELECT
SUBSTR(machine_no, 1,
CASE WHEN INSTR(machine_no, '-', 1, 2) = 0
THEN LENGTH(machine_no)
ELSE INSTR(machine_no, '-', 1, 2)-1
END) as machine_no,
downtime
FROM machine
WHERE location='A1'
) InnerQuery
GROUP BY machine_no
How do I join table WORK and display the month? I'm using Oracle.
Thank you.

Answer 1

The month column's semantics in your expected query result is unclear. Assuming that it is another aggregation "key", then your query would be
select
regexp_substr(M.machine_no, '^[^-]+-[^-]+') as machine_no,
sum(downtime) as total_downtime,
to_char(W.date, 'mm') as month
from machine M
join work W
on W.machine_no = M.machine_no
group by
regexp_substr(M.machine_no, '^[^-]+-[^-]+'),
to_char(W.date, 'mm')
;
Assuming it is a (somehow) aggregated value, let's say via min() function, then your query would be
select
regexp_substr(M.machine_no, '^[^-]+-[^-]+') as machine_no,
sum(downtime) as total_downtime,
min(to_char(W.date, 'mm')) as month
from machine M
join work W
on W.machine_no = M.machine_no
group by
regexp_substr(M.machine_no, '^[^-]+-[^-]+')
;
Both of these, in addition, assume that the (total of A1-100, A1-100-01) in your expected result is just your note, not really a part of the result. But if not, then your query could be something along the lines of
select
regexp_substr(M.machine_no, '^[^-]+-[^-]+') as machine_no,
sum(downtime)||
case when count(1) > 1 then
' (total of '||
listagg(M.machine_no)
within group (order by M.machine_no)||
')'
end
as total_downtime,
to_char(W.date, 'mm') as month
from machine M
join work W
on W.machine_no = M.machine_no
group by
regexp_substr(M.machine_no, '^[^-]+-[^-]+'),
to_char(W.date, 'mm')
;
And even this works because of a few more assumptions about the (unsaid) properties of your machine and work tables, so I'm going to stop my answer here. :-)

Answer 2

User regular expression to take sub string of machine_no and to_char to get the month
WITH machine(machine_no, downtime, location) as (
select 'A1-100-01', 2, 'A1' from dual union all
select 'A1-100', 1.5, 'A1' from dual union all
select 'A1-200', 3, 'A1' from dual union all
select 'CC3-100-01', 0.5, 'CC3' from dual union all
select 'CC3-100', 1.5, 'CC3' from dual),
work(machine_no, ddate) as (
select 'A1-100-01', to_date('2/4/14', 'mm/dd/yyyy') from dual union all
select 'A1-100', to_date('2/14/14', 'mm/dd/yyyy') from dual union all
select 'A1-200', to_date('2/6/14', 'mm/dd/yyyy') from dual union all
select 'CC3-100-01', to_date('3/15/14', 'mm/dd/yyyy') from dual union all
select 'CC3-100', to_date('3/2/14', 'mm/dd/yyyy') from dual)
--End of data preparation
SELECT regexp_substr(m.machine_no, '^\w+-\w+') AS machine_no,
sum(m.downtime) downtime_sum,
to_char(w.ddate , 'MM') MONTH
FROM WORK w
JOIN machine m ON m.machine_no = w.machine_no
WHERE m.location = 'A1'
GROUP BY regexp_substr(m.machine_no, '^\w+-\w+'),
to_char(w.ddate , 'MM');
Output:
| MACHINE_NO | DOWNTIME_SUM | MONTH |
|------------|--------------|-------|
| A1-200 | 3 | 02 |
| A1-100 | 3.5 | 02 |