清理重复数据，建立联合唯一索引
1. 查看重复数据
SELECT * FROM holiday_focamobilerel WHERE (cardnumber, mobile) IN (SELECT cardnumber, mobile FROM holiday_focamobilerel GROUP BY cardnumber, mobile HAVING COUNT(1) > 1);
2. 删除重复数据
- 保留order_id and sub_order_id不为空的
- 如果order_id和sub_order_id都为空，保留id最大的
DELETE FROM holiday_focamobilerel h WHERE (cardnumber, mobile) IN (SELECT cardnumber, mobile FROM holiday_focamobilerel GROUP BY cardnumber, mobile HAVING COUNT(1) > 1) AND h.id NOT IN (select id from holiday_focamobilerel h where h.order_id is not null or h.sub_order_id is not null ) and h.id not in (SELECT MAX(id) FROM holiday_focamobilerel GROUP BY cardnumber, mobile HAVING COUNT(1) > 1);
3. 建立联合唯一约束
alter table holiday_focamobilerel add constraint cardnumber_mobile_key unique("cardnumber","mobile")
原文：https://www.cnblogs.com/weihengblog/p/10320394.html