Oracle 11g Release 2

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CREATE TABLE x
    ("A" int, "B" int)
;

INSERT ALL 
    INTO x ("A", "B")
         VALUES (1, 10)
    INTO x ("A", "B")
         VALUES (1, 20)
    INTO x ("A", "B")
         VALUES (1, 30)
    INTO x ("A", "B")
         VALUES (1, 40)
    INTO x ("A", "B")
         VALUES (2, 50)
    INTO x ("A", "B")
         VALUES (2, 65)
    INTO x ("A", "B")
         VALUES (2, 75)
    INTO x ("A", "B")
         VALUES (1, 89)
    INTO x ("A", "B")
         VALUES (1, 100)
SELECT * FROM dual
;
9 rows affected

select a,min(b), max(b) 
FROM
( select x.*, row_number() OVER ( ORDER BY B ) - 
             row_number() OVER ( PARTITION BY A 
                                 ORDER BY B 
                                 ) as seq from x 
) group by a,seq;


A
MIN(B)
MAX(B)


1
10
40

2
50
75

1
89
100