Question

我有一个从CSV文件中copy创建的临时表，结果包含一些重复的ID。我需要删除任何重复。我尝试过以下方法：

delete from my_table where id in
    (select id from (select count(*) as count, id
        from my_table group by id) as counts where count>1);

然而，这会删除重复的记录，我必须保留一个。

如何只删除带有重复ID的第二条记录？

感谢。

Answer 1

您的查询会删除计数大于1的所有ID，因此会删除所有重复的ID。您需要做的是从重复列表中隔离一条记录并保留：

delete
from   my_table
where  id in     (select   id
                  from     my_table
                  where    some_field in (select   some_field
                                          from     my_table
                                          group by some_field
                                          having   count(id) > 1))
and    id not in (select   min(id)
                  from     my_table
                  where    some_field in (select   some_field
                                          from     my_table
                                          group by some_field
                                          having   count(id) > 1)
                  group by some_field);

编辑修正：P

Answer 2

假设你没有外键关系......

CREATE TABLE "temp"(*column definitions*);

insert into "temp" (*column definitions*)
select *column definitions*
from (
        select *,row_number() over(PARTITION BY id) as rn from "yourtable"
) tm
where rn=1;

drop table "yourtable";

alter table "temp" rename to "yourtable";

删除重复记录，保留一个

2 个答案: