Hi i have a mysql table without primary key and i need to delete the duplicated rows. how can i do so?
嗨，我有一个没有主键的mysql表，我需要删除重复的行。我怎么能这样做？
user_id category_id
1 2
1 3
1 4
1 2
2 2
2 3
2 2
2 个解决方案
#1
17
CREATE TABLE temp SELECT DISTINCT * FROM tablename;
ALTER TABLE tablename RENAME junk;
ALTER TABLE temp RENAME tablename;
#2
2
Since you cannot differentiate 2 identical rows, you cannot delete just one of them. The way you need to think about it is like this:
由于无法区分2个相同的行，因此无法仅删除其中一个行。你需要考虑它的方式是这样的：
insert into new_better_table
select user_id, category_id from old_table group by user_id, category_id
#1
17
CREATE TABLE temp SELECT DISTINCT * FROM tablename;
ALTER TABLE tablename RENAME junk;
ALTER TABLE temp RENAME tablename;
#2
2
Since you cannot differentiate 2 identical rows, you cannot delete just one of them. The way you need to think about it is like this:
由于无法区分2个相同的行，因此无法仅删除其中一个行。你需要考虑它的方式是这样的：
insert into new_better_table
select user_id, category_id from old_table group by user_id, category_id