Delete duplicated records from a table without pk or id or unique columns in mysql

Question

I need to delete all the duplicated records from one of my tables the problem is that there isn\'t any id or unique or key column so I can\'t make something like this:

Answer 1

its pretty simple just make a temporary table and drop the other table then recreate it

CREATE TEMPORARY TABLE IF NOT EXISTS no_dupes AS 
(SELECT * FROM test GROUP BY phone, address, name, cellphone);

TRUNCATE table test;
INSERT INTO test (phone, address, name, cellphone) 
SELECT phone, address, name, cell FROM no_dupes;

WORKING DEMO

Answer 2

I'd use sub query. Something like:

DELETE FROM table1
WHERE EXISTS (
SELECT field1 
FROM table1 AS subTable1 
WHERE table1.field1 = subTable1.field1 and table1.field2 = subTable1.field2)

Haven't try this out though.

Answer 3

there is always a PK per table but you can combine columns as an unique id, so it's possible use a full row as a unique id if you want to... but I don't recommend use a full row, you should search what are the most significant columns that you can use a PK, when you have done that, you can copy the data, if there is no problem the mysql won't copy the duplicate rows.

sorry for my bad english

Answer 4

Adding a unique index (with all the columns of the table) with ALTER IGNORE will get rid of the duplicates:

ALTER IGNORE TABLE table_name
  ADD UNIQUE INDEX all_columns_uq
    (phone, address, name, cellphone) ;

Tested in SQL-Fiddle.

Note: In version 5.5 (due to a bug in the implementation of fast index creation), the above will work only if you provide this setting before the ALTER:

SET SESSION old_alter_table=1 ;