問題:
I have a table user_interactions
with 4 columns: 我有一個表user_interactions
有4列:
user_1
user_2
type
timestamp
The primary key is (user_1,user_2,type)
主鍵是(user_1,user_2,type)
and I want to change to (user_2,user_1,type)
我想更改爲(user_2,user_1,type)
So what I did was : 所以我所做的是:
drop primary key ...
add primary key (user_2,user_1,type)...
and voila... 瞧...
The problem is that database is live on a server. 問題在於數據庫在服務器上處於活動狀態。
So before I could update the primary key, many duplicates already crept in, and they are continuously creeping in. 因此,在我可以更新主鍵之前,許多重複項已經悄悄潛入,並且它們一直在不斷蔓延。
What to do? 該怎麼辦?
What I want to do now is to remove duplicates and keep the ones with the latest timestamp
(which is a column in the table). 我現在想做的是刪除重複項,並保留最新的timestamp
(在表中的一列)。
And then somehow update the primary key again. 然後以某種方式再次更新主鍵。