Oracle 18c

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select version();
ORA-00923: FROM keyword not found where expected

create table test
(
  c       varchar2(10),
  i      INTEGER
);
insert into test
select 'A', level from dual connect by level <= 25
union all
select 'B', level from dual connect by level <= 18
UNION ALL
SELECT 'C', LEVEL FROM DUAL CONNECT BY LEVEL <= 25;
68 rows affected

SELECT
  c, fval1, lval2
FROM
(
  SELECT
    c, i, 

    FIRST_VALUE(i) OVER (PARTITION BY c, TRUNC((i - 1) / 10) 
      ORDER BY c, i ASC) AS fval1,
    
    -- the default frame clause for window functions
    
    FIRST_VALUE(i) OVER (PARTITION BY c, TRUNC((i - 1) / 10)  ORDER BY c, i ASC
      RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)  AS fval2,

    -- the default doesn't work for the LAST_VALUE() fuction - you have to do it
    -- this way.


    LAST_VALUE(i) OVER (PARTITION BY c, TRUNC((i - 1) / 10)  ORDER BY c, i ASC
      RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)  AS lval2

  FROM 
    test
) TAB
GROUP BY c, fval1, lval2
ORDER BY c, fval1;


C
FVAL1
LVAL2


A
1
10

A
11
20

A
21
25

B
1
10

B
11
18

C
1
10

C
11
20

C
21
25