Oracle 21c

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Create table EMP(
        emp_id number,
        emp number,
        code number,
        date_start date,
        date_end date
    );
BEGIN
    Insert into EMP (emp_id,emp,code,date_start,date_end) VALUES (1,100,1,sysdate,sysdate + 1/24);
    Insert into EMP (emp_id,emp,code,date_start,date_end) VALUES (2,100,1,sysdate,sysdate + 1/24);
    Insert into EMP (emp_id,emp,code,date_start,date_end) VALUES (3,100,2,sysdate,sysdate + 1/24);
    Insert into EMP (emp_id,emp,code,date_start,date_end) VALUES (4,100,1,sysdate,sysdate + 1/24);
    END;
/
1 rows affected

SELECT *
FROM   (SELECT emp, code, 24 * (date_end - date_start) AS hours FROM emp)
PIVOT (
  SUM(hours) FOR code IN (
    1 AS code_1,
    2 AS code_2
  )
);


EMP
CODE_1
CODE_2


100
3
1


SELECT emp,
       SUM(CASE code WHEN 1 THEN 24 * (date_end - date_start) END) AS code_1,
       SUM(CASE code WHEN 2 THEN 24 * (date_end - date_start) END) AS code_2
FROM   emp
GROUP BY emp;


EMP
CODE_1
CODE_2


100
3
1