Delete Duplicates Leaving One of Two Identical Records
Without knowing the structure, generically, you can GROUP BY the fields that have been duplicated and store it in a separate table for check purposes, then substitute the old table with the new one.

So, imagine that I have a table my_table with the fields a and b duplicated. I can do:

CREATE TABLE my_table_new (id int primary key auto_increment, a blob, b blob);

SET @i := 0;

INSERT INTO my_table_new SELECT @i := @i + 1, a, b FROM my_table GROUP BY a, b;


The exact query will depend on the older structure, the fields you want to group by, the order in which you want to insert, etc. This example creates an integer primary key from 1 to number of non-duplicate records.