How to delete duplicates on a MySQL table?

Question

I need to DELETE duplicated rows for specified sid on a MySQL table.

How can I do this with an SQL query?

Answer 1

I think this will work by basically copying the table and emptying it then putting only the distinct values back into it but please double check it before doing it on large amounts of data.

Creates a carbon copy of your table

create table temp_table like oldtablename; insert temp_table select * from oldtablename;

Empties your original table

DELETE * from oldtablename;

Copies all distinct values from the copied table back to your original table

INSERT oldtablename SELECT * from temp_table group by firstname,lastname,dob

Deletes your temp table.

Drop Table temp_table

You need to group by aLL fields that you want to keep distinct.