Remove duplicate rows in a table having no primary key

问题

I have a table item that contains items like

name
------
alpha
alpha 
beta
charlie
charlie

In this case how would I delete duplicate rows but one record should remain. The above table does not have any primary key.

回答1:

Try this

DELETE FROM item WHERE GREATEST(0,@num := IF(NAME = @NAME, @num + 1, 0),LEAST(0, LENGTH(@NAME := NAME)))>0

回答2:

Recreate that table:

RENAME TABLE `testTable` TO `testTable2`;

CREATE TABLE `testTable` 
SELECT DISTINCT `name` FROM `testTable2`;

OR Add UNIQUE INDEX on your field.

ALTER IGNORE TABLE `tableName` 
    ADD UNIQUE INDEX (`name`)

来源：https://stackoverflow.com/questions/14357888/remove-duplicate-rows-in-a-table-having-no-primary-key