如何根据其他 2 列选择 1 列的最大值和最小值？

Question

I'm trying to get the max and min date values in column C based on the (column A, column B) unique pair combinations.

Suppose I have a table like:

column_A column_B column_C
A        1        2019-08-11
A        1        2018-11-12
A        1        2017-11-12
A        11       2020-03-03
A        11       2021-01-10
A        11       2021-02-02
B        2        2020-11-11
B        2        2020-12-12

The output I want to get is:

column_A column_B column_C
A        1        2019-08-11
A        1        2017-11-12
A        11       2020-03-03
A        11       2021-02-02
B        2        2020-11-11
B        2        2020-12-12

My attempt query has been taking 20 mins to run with no output yet (just tried to get max date from column C for now):

SELECT column_A, column_B, column_C FROM table_name
WHERE column_C IN (
   SELECT MAX(column_C) FROM table_name
   GROUP BY column_A, column_B
)

Answer 1

Just use two conditions:

select t.*
from t
where column_c = (select max(t2.colc)
                  from table_name t2
                  where t2.column_A = t.column_A and t2.column_B = t.column_B
                 ) or
      column_c = (select min(t2.colc)
                  from table_name t2
                  where t2.column_A = t.column_A and t2.column_B = t.column_B
                 ) ;
  

Answer 2

You can use two queries that group by column_a and column_b , one with the max and one with the min of column_c , and then union all them:

SELECT   column_a, column_b, MAX(column_c)
FROM     table_name
GROUP BY column_a, column_b
UNION ALL
SELECT   column_a, column_b, MIN(column_c)
FROM     table_name
GROUP BY column_a, column_b

Answer 3

you can create a temporary view and GROUP BY the desired columns

select column_a,column_b,max(column_c) as max_column_c
from (select column_a,column_b,column_c,to_char(column,'YYYY') as year
from table_t) aa
group by column_a,column_b,year