How to put all rows at the same level in SQL? - mysql

Question

Trying to use this query for a procedure where a client ask for a loan:
select loan_id,
CASE WHEN status = 'document_sent' then date ELSE NULL END as document_sent,
CASE WHEN status = 'document_rejected' then date ELSE NULL END as document_rejected
from table
and status in ('document_sent', 'document_rejected')
order by 2 asc, 3 asc
And this is the result:
loan_id
document_sent
doc_rejected
123
2021-03-01 14:52
123
2021-03-01 14:57
123
2021-03-01 15:33
123
2021-03-01 14:54
123
2021-03-01 15:00
123
2021-03-01 15:39
I would like to have something like this:
loan_id
document_sent
doc_rejected
123
2021-03-01 14:52
2021-03-01 14:54
123
2021-03-01 14:57
2021-03-01 15:00
123
2021-03-01 15:33
2021-03-01 15:39
Is it possible? Thanks

Answer 1

If we don't make any assumptions about the absence/presence of each type of record:
select
coalesce(a.loan_id,b.loan_id) as loan_id
, ds.date as document_sent
, dr.date as document_rejected
from
(select * from tbl where status='document_sent') ds
full outer join
(select * from tbl where status='document_rejected') dr
on ds.loan_id=dr.loan_id
If you know that one or the other status is always present, then it can be a little simplified (can be turned into left join), or if both records are expected to be there it can be simplified to:
select
a.loan_id
, ds.date as document_sent
, dr.date as document_rejected
from
tbl ds
inner join
tbl dr
on ds.loan_id=dr.loan_id
and ds.status='document_sent'
and dr.status='document_rejected'
If `full outer join is not available:
select
coalesce(a.loan_id,b.loan_id) as loan_id
, ds.date as document_sent
, dr.date as document_rejected
from
(select * from tbl where status='document_sent') ds
left join
(select * from tbl where status='document_rejected') dr
on ds.loan_id=dr.loan_id
union all
select
coalesce(a.loan_id,b.loan_id) as loan_id
, ds.date as document_sent
, dr.date as document_rejected
from
(select * from tbl where status='document_sent') ds
right join
(select * from tbl where status='document_rejected') dr
on ds.loan_id=dr.loan_id
where ds.loan_id is null
Thanks #nbk for pointing out.
You could also use MIN/MAX (although we don't want to find min/max of anything, we want to take advantage of their behaviour that 1.they accept dates, and 2. they ignore null values, 3.they are used with GROUP BY to group rows together):
select
loan_id
, min(case when status='document_sent'
then ds.date else NULL end) as document_sent
, min(case when status='document_rejected'
then ds.date else NULL end) as document_rejected
from
tbl
group by id