Question

我有一个mysql表，每行有20个字段。其中包括：

table: origin, destination, date, price

现在，我想删除任何仅与一组特定字段重复的行：origin, destination, date。

我试过了：

delete from mytable where id not in 
    (select id from (
            SELECT MAX(p.id) as id from mytable p group by p.origin, p.destination, p.date
    ) x)

问题：这会保留最高id的行（表示：上次添加）。

相反，我只想保留价格最低的行。但是如何？

旁注：我无法添加唯一索引，因为该表用于LOAD DATA的大量插入，并且不应该抛出错误。在负载时我不知道哪一行是最好的价格＆＃34;之一。

此外，我不想引入任何附加或临时表复制到另一个。只需修改现有表格。

Answer 1

自我加入解决方案：

delete t1
from yourtable t1
join yourtable t2
on t1.origin = t2.origin
and t1.destination = t2.destination
and t1.date = t2.date
and t1.price > t2.price

Answer 2

delete t1 
from mytable t1
left join 
(
    SELECT origin, destination, date, min(price) as price
    from mytable
    group by origin, destination, date
) t2 on t1.origin = t2.origin
    and t1.destination = t2.destination
    and t1.date = t2.date 
    and t1.price = t2.price
where t2.origin is null

如何在mysql中保留一行并删除重复项？

2 个答案: