Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

WITH job(employee_id, job, start_dt) AS
(
  SELECT 1,  'abc', date'2021-01-01' FROM dual UNION ALL
  SELECT 1,  'def', date'2021-05-01' FROM dual UNION ALL
  SELECT 2,  'xyz', date'2021-06-01' FROM dual UNION ALL
  SELECT 2,  'rfd', date'2021-08-01' FROM dual UNION ALL
  SELECT 2,  'hgf', date'2021-07-01' FROM dual UNION ALL
  SELECT 2,  'esd', date'1999-01-01' FROM dual
), j AS
(  
 SELECT ROW_NUMBER() OVER (PARTITION BY employee_id ORDER BY start_dt) AS rn,
        j.*
   FROM job j
)
SELECT employee_id, 
       MAX(CASE WHEN rn = 1 THEN job END) AS job_a,
       MAX(CASE WHEN rn = 1 THEN start_dt END) AS start_dt_a,  
       MAX(CASE WHEN rn = 2 THEN job END) AS job_b,
       MAX(CASE WHEN rn = 2 THEN start_dt END) AS start_dt_b,
       MAX(CASE WHEN rn = 3 THEN job END) AS job_c,
       MAX(CASE WHEN rn = 3 THEN start_dt END) AS start_dt_c,
       MAX(CASE WHEN rn = 4 THEN job END) AS job_d,
       MAX(CASE WHEN rn = 4 THEN start_dt END) AS start_dt_d              
  FROM j
 GROUP BY employee_id
 ORDER BY employee_id

EMPLOYEE_ID	JOB_A	START_DT_A	JOB_B	START_DT_B	JOB_C	START_DT_C	JOB_D	START_DT_D
1	abc	01-JAN-21	def	01-MAY-21	null	null	null	null
2	esd	01-JAN-99	xyz	01-JUN-21	hgf	01-JUL-21	rfd	01-AUG-21