[Essay★Tens of millions of mailboxes: more than 0.1 billion pieces of data are repeated by email field recently. What data? You know!

Recently, more than 0.1 billion pieces of data are repeated by email field. What data? You know!

More than 0.1 billion pieces of data are duplicated by email error, with more than 60 million remaining.

The following is an SQL statement. It is really not so fun to use a massive amount of data. A simple SQL statement will take a dozen minutes and take half an hour ....

Select min (ID) as ID into TMP from tbl_alluser group by email -- first de-duplicate by mail and then write the ID to the temporary table

Insert into tbl_alluser_new
Select username, email, source from tbl_alluser right join TMP on tbl_alluser.id = TMP. ID -- then write data to the new table by the ID in the temporary table

 Better SQL!