show only MAX rows - sql

Question

i have a table which shows me workhours of postoffices, the problem is that sometimes there are duplicates: for example i have saturday showing twice from one postoffice with the same time.
Solution is to show only 1 saturday with MAX(ID), but i can't deal with that and tha think is that i don't have to show id in select.
this is my script
SELECT h.ID,
h.POSTINDEX,
H.LONGNAME_UA,
h.SHORTNAME_UA,
pt.LONGNAME_UA,
h.parent_Id,
WORKCOMMENT,
INTERVALTYPE,
TO_CHAR(TFROM, 'HH24:MI') AS TFROM,
TO_CHAR(TTO, 'HH24:MI'),
WD.NAME_UA,
WD.NAME_EN,
WD.NAME_RU,
WD.SHORTNAME_UA,
pt.isVPZ,
lr.NAME_UA,
lr.CODE
FROM ADDR_PO_WORKSCHEDULE tt
LEFT JOIN ADDR_POSTOFFICE h
ON tt.POSTOFFICE_ID = h.ID
INNER JOIN mdm_lockReason lr
ON lr.id = H.LOCK_REASON
INNER JOIN ADDR_POSTOFFICEtype pt
ON pt.ID = H.POSTOFFICETYPE_ID
INNER JOIN ADDR_PO_WORKDAYS wd
ON wd.ID = tt.dayofweek
where tt.datestop = TO_DATE('9999-12-31','YYYY-MM-DD') AND tt.postoffice_id = 8221
HAVING MAX(tt.ID)
ORDER BY h.postIndex,
h.POSTOFFICETYPE_ID,
dayofweek,
intervaltype,
tFrom,
tto
as you can see there i've add HAVING MAX(tt.ID) but i understand that it is incorrect and don't know how to solve that. help please!

Answer 1

You can use row_number():
with t as (
<your query here with no `having` and with tt.id as tt_id>
)
select t.*
from (select t.*, row_number() over (order by tt_id desc) as seqnum
from t
) t
where seqnum = 1;

Answer 2

If the source of your duplicate rows is coming from the ADDR_PO_WORKSCHEDULE table, then you can just de-dupe it before you use it in the rest of your query:
SELECT
h.ID, h.POSTINDEX, h.LONGNAME_UA, h.SHORTNAME_UA, pt.LONGNAME_UA, h.parent_Id,
WORKCOMMENT, INTERVALTYPE, TO_CHAR(TFROM, 'HH24:MI') AS TFROM, TO_CHAR(TTO, 'HH24:MI'),
WD.NAME_UA, WD.NAME_EN, WD.NAME_RU, WD.SHORTNAME_UA, pt.isVPZ, lr.NAME_UA, lr.CODE
FROM (
SELECT src.*
FROM (
SELECT t.*,
ROW_NUMBER() OVER(
PARTITION BY tt.postoffice_id, tt.dayofweek -- Group by post office / day of week
ORDER BY <order_columns> -- Rank rows within each group
) AS RowNum
FROM ADDR_PO_WORKSCHEDULE t
) src
WHERE RowNum = 1
) tt
LEFT JOIN ADDR_POSTOFFICE h ON tt.POSTOFFICE_ID = h.ID
INNER JOIN mdm_lockReason lr ON lr.id = H.LOCK_REASON
INNER JOIN ADDR_POSTOFFICEtype pt ON pt.ID = H.POSTOFFICETYPE_ID
INNER JOIN ADDR_PO_WORKDAYS wd ON wd.ID = tt.dayofweek
WHERE tt.datestop = TO_DATE('9999-12-31','YYYY-MM-DD')
AND tt.postoffice_id = 8221
ORDER BY h.postIndex, h.POSTOFFICETYPE_ID, dayofweek, intervaltype, tFrom, tto
Just replace with the columns you want to use to decide which of the "duplicate" rows to keep. If the order doesn't matter, just remove the ORDER BY altogether.
Also, you may want to qualify all column references, since you are selecting from multiple tables.

Answer 3

You can use analytical function as following:
Select * from
(Select <your select column list>,
Row_number() over (partition by h.postindex, trunc(tfrom) order by tt.id desc nulls last) as rn
From <from clause>
Where <where clause>
)
Where rn = 1;
group by is not needed.