Oracle - Max value from each date with date/time - sql

Question

I have table with column Date with timestamp, value in seconds and have query like
Table
2017-01-10 06:45:00 PM 1119
2017-01-10 03:30:00 PM 1054
2017-01-11 11:15:00 PM 379
2017-01-10 06:30:00 PM 377
2017-01-11 09:15:00 PM 375
Query
SELECT
TO_char(DtTm,'YYYY-MM-DD hh:mi:ss AM') As DataDt,
max(MaxSec) as Wait_sec, DtTimeTable.HrID,
FROM DtTimeTable
WHERE DtTimeTable.HrName in ('Dept1', 'Dept2', 'Dept3')
AND DtTm BETWEEN to_date('2017-01-08 00:00:00', 'YYYY-MM-DD hh24:mi:ss')
AND to_date('2017-01-10 23:59:59', 'YYYY-MM-DD hh24:mi:ss')
Group by TO_char(DtTm,'YYYY-MM-DD hh:mi:ss AM'),DtTimeTable.HrID
order by Wait_sec desc
This gives me All records and if i add
select * from
Query1 --(above)
where rownum <1 order by Wait_sec desc, Datadt desc;
I am only getting highest value of result set
How can get DatewithTime, Maxvalue for each date like
2017-01-10 06:45:00 PM 1119
2017-01-11 11:15:00 PM 379

Answer 1

Try something like this:
Select *
From (
Select t.*,
Row_number() over(partition by trunc(datecol) order by value desc nulls last) rn
From yourtable t
) where rn = 1;
It assign row number within date based on descending order your value column and then filters to get the first row

Answer 2

The solution below uses grouping, the MAX() aggregate function, and the FIRST/LAST function (with KEEP DENSE_RANK). If for a date the same highest value is reached more than once, it picks the first time during the day that the value was reached.
with
test_data( dt, val ) as (
select to_date('2017-01-10 06:45:00 PM', 'yyyy-mm-dd hh:mi:ss AM'), 1119 from dual
union all
select to_date('2017-01-10 03:30:00 PM', 'yyyy-mm-dd hh:mi:ss AM'), 1054 from dual
union all
select to_date('2017-01-11 11:15:00 PM', 'yyyy-mm-dd hh:mi:ss AM'), 379 from dual
union all
select to_date('2017-01-10 06:30:00 PM', 'yyyy-mm-dd hh:mi:ss AM'), 377 from dual
union all
select to_date('2017-01-11 09:15:00 PM', 'yyyy-mm-dd hh:mi:ss AM'), 375 from dual
)
-- end of test data; SQL query begins below this line (use actual table and column names)
select min(dt) keep(dense_rank last order by val) as dt, max(val) as val
from test_data
group by trunc(dt)
order by dt -- if needed
;
DT VAL
---------------------- ----------
2017-01-10 06:45:00 PM 1119
2017-01-11 11:15:00 PM 379
2 rows selected.