Oracle 18c

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CREATE TABLE test (a INT, name VARCHAR2(10));
   
INSERT INTO test(a, name) 
SELECT 1, 'John' FROM DUAL UNION ALL
SELECT 2, 'bob'  FROM DUAL;
2 rows affected

SELECT t.*, ASCII(SUBSTR(name, 1, 1)) FROM test t;

A
NAME
ASCII(SUBSTR(NAME,1,1))

1
John
74

2
bob
98

ALTER SESSION SET NLS_COMP = 'BINARY';
ALTER SESSION SET NLS_SORT = 'BINARY';
SELECT MIN(name), MAX(name) FROM test;

MIN(NAME)
MAX(NAME)

John
bob

SELECT MIN(name) KEEP (DENSE_RANK FIRST ORDER BY NLSSORT(name, 'NLS_SORT=BINARY_CI'))
         AS min,
       MAX(name) KEEP (DENSE_RANK LAST ORDER BY NLSSORT(name, 'NLS_SORT=BINARY_CI'))
         AS max
FROM   test;

MIN
MAX

bob
John

ALTER SESSION SET NLS_COMP = 'LINGUISTIC';
ALTER SESSION SET NLS_SORT = 'BINARY';
SELECT MIN(name), MAX(name) FROM test;

MIN(NAME)
MAX(NAME)

John
bob

ALTER SESSION SET NLS_COMP = 'BINARY';
ALTER SESSION SET NLS_SORT = 'BINARY_CI';
SELECT MIN(name), MAX(name) FROM test;

MIN(NAME)
MAX(NAME)

John
bob

ALTER SESSION SET NLS_COMP = 'LINGUISTIC';
ALTER SESSION SET NLS_SORT = 'BINARY_CI';
SELECT MIN(name), MAX(name) FROM test;

MIN(NAME)
MAX(NAME)

bob
John