原思路：
1、A库中多张表做聚合查询（结果应与B库中的表结构一致）；
2、将其导出成insert语句；
3、修改insert语句冰在B库中执行；
缺点：
1、执行insert语句时需要改变表的名称；
2、查出的结果数据的字段名必须与要导入的表结构字段名一致，否则需要人工手动的去修改字段名；
3、导入时若字段属性不为空，出现null值时报执行异常；
新思路：
1、直接将查出来的结果用字符串拼接方法 CONCAT ，将其拼接成 INSERT 字符串，只能是成列，直接粘贴执行即可，具体SQL如下：
SELECT
CONCAT(
"INSERT INTO `channel_bill` (`id`, `apply_no`, `waybill_no`, `bill_type`, `title_type`, `title`, `taxpayer_no`, `email`, `content`, `total_amount`, `address`, `phone`, `bank_name`, `bank_no`, `user_code`, `memo`, `status`, `fail_reson`, `bill_code`, `bill_no`, `url`, `audit_status`, `billing_time`, `service_phone`, `is_delete`, `latest_time`, `record_version`, `created_by`, `creater_time`, `created`, `updated_by`, `updated`) VALUES (",
IFNULL(i.item_id, ''),
",'",
IFNULL(i.apply_no, ''),
"','",
IFNULL(i.waybill_no, ''),
"','",
IFNULL(a.bill_type, ''),
"','",
IFNULL(a.title_type, ''),
"','",
IFNULL(a.title, ''),
"','",
IFNULL(a.taxpayer_no, ''),
"','",
IFNULL(a.email, ''),
"','",
IFNULL(a.content, ''),
"','",
IFNULL(i.total_amount, ''),
"','",
IFNULL(a.address, ''),
"','",
IFNULL(a.phone, ''),
"','",
IFNULL(a.bank_name, ''),
"','",
IFNULL(a.bank_no, ''),
"','",
IFNULL(a.user_code, ''),
"','",
IFNULL(a.memo, ''),
"','",
IFNULL(a. STATUS, ''),
"','",
IFNULL(a.failReson, ''),
"','",
IFNULL(a.bill_code, ''),
"','",
IFNULL(a.bill_no, ''),
"','",
IFNULL(a.url, ''),
"','",
IFNULL(a.audit_status, ''),
"','",
IFNULL(a.billing_time, ''),
"','",
IFNULL(a.service_phone, ''),
"','",
IFNULL(i.is_delete, ''),
"','",
IFNULL(i.latest_time, ''),
"','",
IFNULL(i.record_version, ''),
"','",
IFNULL(i.creater, ''),
"','",
IFNULL(i.creater_time, ''),
"','",
IFNULL(i.creater_time, ''),
"','",
IFNULL(i.modifier, ''),
"','",
IFNULL(i.modifier_time, ''),
"');"
)
FROM
wechat_bill_item i
LEFT JOIN wechat_bill_apply a ON a.apply_no = i.apply_no;
执行结果如下：
这样出来的insert语句就不需要认为的修改，在编写select语句的时候就能将其修改成自己想要的字段，很灵活；
