flink sql cdc sum 结果出现NULL

[kandy.wang]

--mysql表
CREATE TABLE IF NOT EXISTS `mysql_realtime_leaving_price_spu_index_agg`(
   `id` INT UNSIGNED AUTO_INCREMENT,
   `spu_id` BIGINT NOT NULL,
   `leaving_price`  DECIMAL(10, 5)
   PRIMARY KEY ( `id` ),
   unique key idx_spu_id (spu_id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8


--flink表
CREATE TABLE hive.temp_flink.mysql_realtime_leaving_price_spu_index_agg (
   `spu_id` BIGINT ,
   `leaving_price`  DECIMAL(10, 5),
    PRIMARY KEY ( `spu_id`) NOT ENFORCED
) WITH (
  'connector' = 'jdbc',
   'url' = 'jdbc:mysql://...',
   'table-name' = 'mysql_realtime_leaving_price_spu_index_agg',
   'username' = '...',
   'password' = '..'
);


--binlog 2mysql

insert into hive.temp_flink.mysql_realtime_leaving_price_spu_index_agg

SELECT v_spu_id as spu_id,sum(leaving_num*price) as leaving_price

FROM hive.database.table

group by v_spu_id;


hive.database.table是指向公司自己的kafka，实现了类似cannal cdc的那4种消息格式。


问题是 mysql结果表 leaving_price 出现很多NULL的情况，看了一下数据leaving_num  price 
字段都不可能出现NULL的情况。就不清楚为啥结果表可能会为NULL。
有什么好的排查思路么？