MySQL 5.7

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id	cID	event_type	delivery_estimate	delivered_time	complete_time	plan_offer_quantity	order_quantity	received
1	46902	offer	2020-02-03	null	null	6145	null	null
2	46902	order	2020-02-03	null	null	null	2145	null
3	46902	stock_in	2020-02-03	2020-02-10	null	null	null	null
4	55519	offer	2020-05-09	null	null	4337	null	null
5	55519	order	2020-05-09	null	null	null	4018	null
6	55519	stock_in	2020-05-09	2020-05-12	2020-07-08	null	null	3989

SELECT
  id,
  cID,
  event_type, 
  'delivered' AS sub_event_type, 
  delivered_time AS event_date,
  CASE WHEN order_quantity IS NOT NULL THEN order_quantity
       ELSE (SELECT order_quantity 
             FROM PDW_FCT_Logistics AS ss
             WHERE ss.cID = PDW_FCT_Logistics.cID
             AND ss.event_type = 'order')
  END AS quantity
  FROM PDW_FCT_Logistics
  WHERE event_type = 'stock_in' AND delivered_time IS NOT NULL

UNION ALL

SELECT
  id,
  cID,
  event_type,
  'completed' AS sub_event_type,
  complete_time AS event_date,
  received as quantity
  FROM PDW_FCT_Logistics
  WHERE event_type = 'stock_in' AND complete_time IS NOT NULL

UNION ALL

SELECT
  id,
  cID,
  event_type, 
  NULL AS sub_event_type,
  delivery_estimate AS event_date,
  plan_offer_quantity AS quantity
  FROM PDW_FCT_Logistics
  WHERE event_type = 'offer'

UNION ALL

SELECT
  id,
  cID,
  event_type, NULL AS sub_event_type,
  delivery_estimate AS event_date,
  order_quantity AS quantity
  FROM PDW_FCT_Logistics
  WHERE event_type = 'order'

ORDER BY id;

id	cID	event_type	sub_event_type	event_date	quantity
1	46902	offer	null	2020-02-03	6145
2	46902	order	null	2020-02-03	2145
3	46902	stock_in	delivered	2020-02-10	2145
4	55519	offer	null	2020-05-09	4337
5	55519	order	null	2020-05-09	4018
6	55519	stock_in	delivered	2020-05-12	4018
6	55519	stock_in	completed	2020-07-08	3989