MySQL deletes duplicate data from the database (subject to some data)

MySQL deletes duplicate data from the database (subject to some data)
Delete from zqzrdp

Where tel in (select min (dpxx_id) from zqzrdp group by tel having count (tel)> 1 );

Execution, error reported

Exception: you cannot specify the update of the target table in the FROM clause. It's silly. MySQL cannot be written like this, which is depressing.

However, you can only perform step-by-step operations.

The following code is also written by netizens. It cannot run on my machine.

1. query the records to be deleted. A record is retained.

The Code is as follows:	Copy code
Select. id,. subject,. else er from test1 a left join (select c. subject, c. cycler, max (c. id) as bid from test1 c where status = 0 group by receiver, SUBJECT having count (1)> 1) B on. id <B. bid where. subject = B. subject and. worker ER = B. aggreger and. id <B. bid

2. Delete duplicate records. Only one record is retained. Note: subject and aggreger must be indexed. Otherwise, it will be slow.

The Code is as follows:	Copy code
Delete a from test1 a, (select c. subject, c. cycler, max (c. id) as bid from test1 c where status = 0 group by consumer er, SUBJECT having count (1)> 1) B where. subject = B. subject and. worker ER = B. aggreger and. id <B. bid;

3. Search for redundant duplicate records in the Table. duplicate records are determined based on a single field (peopleId ).

The Code is as follows:	Copy code
Select * from people Where peopleId in (select peopleId from people group by peopleId having count (peopleId)> 1)

4. Delete unnecessary duplicate records in the Table. Repeat records are determined based on a single field (eagleid), leaving only the records with the smallest rowid

The Code is as follows:	Copy code
Delete from people Where peopleId in (select peopleId from people group by peopleId having count (peopleId)> 1) And rowid not in (select min (rowid) from people group by peopleId having count (peopleId)> 1)

5. Delete redundant record (multiple fields) in the table, with only the records with the smallest rowid

The Code is as follows:	Copy code
Delete from vitae Where (a. peopleId, a. seq) in (select peopleId, seq from vitae group by peopleId, seq having count (*)> 1) And rowid not in (select min (rowid) from vitae group by peopleId, seq having count (*)> 1)