Hi， 麻烦帮忙看下这个问题：
创建 View promotionTable:
SELECT *, 'CN' as country, id as pid
FROM promotion_cn_rule_tab
UNION
SELECT *, 'JP' as country, id as pid
FROM promotion_jp_rule_tab
FLink SQL Query：
SELECT t1.country, t1.promotionId, t1.orderId,
CASE WHEN t2.pid IS NULL THEN 'Rebate'
ELSE 'Rebate'
END AS rebate
FROM eventTable AS t1
LEFT JOIN promotionTable
/*+ OPTIONS('streaming-source.enable' = 'false',
'streaming-source.partition.include' = 'all',
'lookup.join.cache.ttl' = '5 m') */
FOR SYSTEM_TIME AS OF t1.procTime AS t2
ON t1.promotionId = t2.pid
AND t1.country = t2.country
如果去掉 Hive 表的 union ，只保留一个国家的 Hive 表，可以run 成功，但是如果 Union 两张表的话，会得到错误：
Caused by: org.apache.flink.table.api.ValidationException: Currently the
join key in Temporal Table Join can not be empty
