Select from group by based on case statement

Based on a table like this I want to group by PRODID, then select a row based on a case statement. Case statement being if IND1 = 1 select row, else if IND2 = 1 select row, else select row with max DATE. If multiple indicators within a group are 1 select row with the max date from the group of indicators being 1.

---

PRODID   IND1       IND2       DATE
---------------------------------------------------
1          1         0      4/24/2020
1          0         0      1/2/2020
1          1         0      1/1/2020
2          0         1      4/24/2020
2          0         1      1/1/2020
3          0         0      4/24/2020
3          0         0      1/1/2020
4          1         0      2/2/2020
4          0         1      4/24/2020
4          0         1      4/24/2020

---

PRODID   IND1       IND2       DATE
---------------------------------------------------
1          1         0      4/24/2020
2          0         1      4/24/2020
3          0         0      4/24/2020
4          1         0      2/2/2020

Answer

One method uses row_number():

select t.*
from (select t.*,
             row_number() over (partition by prodid
                                order by (case when ind1 > 0 then 1 else 2 end),
                                         (case when ind1 = 0 and ind2 > 0 then 1 else 2 end),
                                         date desc
                               ) as seqnum

      from t
     ) t
where seqnum = 1;

If you like arithmetic, this can be simplified to:

select t.*
from (select t.*,
             row_number() over (partition by prodid
                                order by ind1 desc, ind2 * (1 - ind1) desc, date desc
                               ) as seqnum

      from t
     ) t
where seqnum = 1;

Note that one trick in putting the logic together is ensuring that the first row is used in the following situation:

1       0      0      2020-01-21
1       1      0      2020-01-20
1       1      1      2020-01-19

This is why you can’t use order by ind1 desc, ind2 desc, date desc (which is quite tempting).