Subtract Max and Min from same column - sql

Question

select
d.FK_SOCRD_ID,
d.SUBJECT_NUMBER,
c.PTLASTNAME || ', ' || c.PTFIRSTNAME as "Patient name",
min(b.created) as Data Entry 1,
max(b.created) as Data Entry 2,
min(b.created) - max(b.created)
|| ' days and '
|| TO_CHAR(to_date('01/01/2000', 'MM-DD-YYYY')
+ (b.created - b.created), 'HH24:MI:SS' ) AS Diff
FROM
CR_MDT a
full outer join CR_MDT_VERIFY b
on a.CR_MDT_ID = b.FK_CR_MDT_ID
left join patient c
on a.FK_SOCRD_ID = c.SOCRD_ID
left join PT_STUDY d
on c.SOCRD_ID = d.FK_SOCRD_ID
where
a.CR_MDT_DT between TO_DATE('01/01/2017', 'mm/dd/yyyy')
and TO_DATE('12/31/2017', 'mm/dd/yyyy')
group by
d.FK_SOCRD_ID,
d.SUBJECT_NUMBER,
c.PTLASTNAME,
c.PTFIRSTNAME,
b.created
How can I subtract the max(b.created) from min(b.created)? I'm stuck on this part:
|| TO_CHAR(to_date('01/01/2000', 'MM-DD-YYYY')
+ (b.created - b.created), 'HH24:MI:SS' ) AS Diff
I need help on how to write the subtraction part since b.created max and min are from the same column.

Answer 1

You can put that query in a subquery and do the subtraction outside:
SELECT *
, max_created - min_created as date_difference
FROM
(
SELECT d.FK_SOCRD_ID
, d.SUBJECT_NUMBER
, c.PTLASTNAME || ', ' || c.PTFIRSTNAME AS "Patient name"
, min(b.created) AS min_created
, max(b.created) AS max_created
FROM CR_MDT a
FULL JOIN CR_MDT_VERIFY b
ON a.CR_MDT_ID = b.FK_CR_MDT_ID
LEFT JOIN patient c
ON c.SOCRD_ID = a.FK_SOCRD_ID
LEFT JOIN PT_STUDY d
ON d.FK_SOCRD_ID = c.SOCRD_ID
WHERE a.CR_MDT_DT BETWEEN TO_DATE('01/01/2017', 'mm/dd/yyyy') AND TO_DATE('12/31/2017', 'mm/dd/yyyy')
GROUP BY d.FK_SOCRD_ID
, d.SUBJECT_NUMBER
, c.PTLASTNAME
, c.PTFIRSTNAME
) subq
You might have to change the datediff function depending on the dbms you are using.
EDIT: I updated the date subtraction part now that i know you use Oracle.

Answer 2

You can use floor(), leave only fractional part of difference and convert it to hh24:mi:ss, like here:
select id, mx, mn, floor(diff) ||' days and '||
to_char(trunc(sysdate) + diff - floor(diff), 'hh24:mi:ss') diff
from (select id, max(created) mx, min(created) mn,
max(created) - min(created) diff
from test group by id)
Test data:
create table test (id number(3), created date);
insert into test values (1, timestamp '2017-09-12 01:00:00');
insert into test values (1, timestamp '2017-11-05 11:24:17');
insert into test values (1, timestamp '2017-12-15 13:42:05');
insert into test values (2, timestamp '2017-01-05 11:00:00');
insert into test values (2, timestamp '2017-06-05 23:12:56');
Result:
ID MX MN DIFF
---- ------------------- ------------------- ---------------------
1 2017-12-15 13:42:05 2017-09-12 01:00:00 94 days and 12:42:05
2 2017-06-05 23:12:56 2017-01-05 11:00:00 151 days and 12:12:56

Answer 3

Here is what gave me the desired result:
SELECT d.FK_SOCRD_ID,
d.SUBJECT_NUMBER,
c.PTLASTNAME || ', ' || c.PTFIRSTNAME AS "Patient name",
min(b.created) AS min_created,
max(b.created) AS max_created,
trunc(max(b.created)) - trunc(min(b.created)) || ' days' AS Diff
FROM CR_MDT a
FULL JOIN CR_MDT_VERIFY b
ON a.CR_MDT_ID = b.FK_CR_MDT_ID
LEFT JOIN patient c
ON c.SOCRD_ID = a.FK_SOCRD_ID
LEFT JOIN PT_STUDY d
ON d.FK_SOCRD_ID = c.SOCRD_ID
WHERE a.CR_MDT_DT BETWEEN TO_DATE('01/01/2017', 'mm/dd/yyyy') AND TO_DATE('12/31/2017', 'mm/dd/yyyy')
GROUP BY d.FK_SOCRD_ID,
d.SUBJECT_NUMBER,
c.PTLASTNAME,
c.PTFIRSTNAME