1. mysql锁表之后报错：Mysql错误: ERROR 1205: Lock wait timeout exceeded

      解决的办法：   select * from information_schema.innodb_trx;
                              kill "trx_mysql_thread_id";

2. 关联删除：

DELETE hk_hold from margin_detail, category where margin_detail.trade_date = 20200227 and margin_detail.ts_code = category.key;

3.关联查询：

select hk_hold from margin_detail, category where margin_detail.trade_date = 20200227 and margin_detail.ts_code = category.key;