code.rb

SELECT timeline_items.* FROM (
  
  # Query 1 
  SELECT lead_alerts.id AS id, lead_alerts.action AS body, users.first_name AS first_name, users.last_name AS last_name, lead_alerts.due_on AS date, "lead_alerts" AS model 
  FROM `lead_alerts` LEFT OUTER JOIN `users` ON `users`.`id` = `lead_alerts`.`author_id`   
  WHERE `lead_alerts`.`lead_id` = 1 
  UNION ALL 
  
  # Query 2
  SELECT completed_lead_alerts.id AS id, lead_alerts.action AS body, users.first_name AS first_name, users.last_name AS last_name, completed_lead_alerts.completed_on AS date, "completed_lead_alerts" AS model 
  FROM `completed_lead_alerts` 
  INNER JOIN `lead_alerts` ON `lead_alerts`.`id` = `completed_lead_alerts`.`lead_alert_id` 
  INNER JOIN `users` ON `users`.`id` = `completed_lead_alerts`.`completor_id` 
  WHERE `lead_alerts`.`lead_id` = 1 
  UNION ALL 
  
  # Query 3
  SELECT notes.id AS id, notes.body AS body, users.first_name AS first_name, users.last_name AS last_name, notes.date AS date, "notes" AS model FROM `notes` 
  INNER JOIN `users` ON `users`.`id` = `notes`.`author_id` 
  WHERE `notes`.`lead_id` = 1 
  UNION ALL 
  
  # Query 4
  SELECT lead_transitions.id AS id, lead_transitions.to_state AS body, "placeholder" AS first_name, "placeholder" AS last_name, lead_transitions.created_at AS date, "lead_transitions" AS model 
  FROM `lead_transitions` 
  WHERE `lead_transitions`.`lead_id` = 1
) AS timeline_items 
WHERE (timeline_items.date <= '2018-11-11 10:07:33.672915') 
ORDER BY timeline_items.date DESC