UPDATE FROM SELECT

mysql.sql

UPDATE user_assets AS ua
INNER JOIN (
  SELECT 
    ua.user_id,
    ua.instance_id,
    uas.state,
    uas.payload,
    uas.history
  FROM user_assets AS ua
  LEFT JOIN user_asset_states AS uas ON uas.user_id = ua.user_id AND uas.instance_id = ua.instance_id
  WHERE 
       uas.state   IS NOT NULL
    OR uas.payload IS NOT NULL
    OR uas.history IS NOT NULL
) AS t ON t.user_id = ua.user_id AND t.instance_id = ua.instance_id
SET 
  ua.state = t.state, 
  ua.payload = t.payload, 
  ua.history = t.history