SELECT @rowid:=@rowid+1 as rowid
FROM table1,(SELECT @rowid:=0) as init
ORDER BY sorter_field

但是,您无法在要从子查询中删除的表上进行排序.

UPD：那就是您需要创建一个临时表,将测距子查询插入临时表,并通过加入临时表(原始表中删除)删除原始表(您将需要一些唯一的行标识符)：

CREATE TEMPORARY TABLE duplicates ...

INSERT INTO duplicates (rowid,field1,field2,some_row_uid)
SELECT
  @rowid:=IF(@f1=field1 AND @f2=field2,@rowid+1,0) as rowid,@f1:=field1 as field1,@f2:=field2 as field2,some_row_uid
FROM testruns t,(SELECT @rowid:=NULL,@f1:=NULL,@f2:=NULL) as init
ORDER BY field1,field2 DESC;

DELETE FROM my_table USING my_table JOIN duplicates
  ON my_table.some_row_uid = duplicates.some_row_uid AND duplicates.rowid > 0

既然这是一次性的操作,这不应该带来太多的开销.