SQLite, update one row with another row data
For MySQL (the question is MySQL-tagged)
UPDATE table t1, table t2
SET t1.field1=t2.field1, t1.field2 = t2.field2, ...
WHERE
      /* copy one record                     */
/*    t1.id = 123 AND t2.id = 456                       */
      /* copy a bunch of consecutive records */
/*    t1.id BETWEEN 111 AND 123 AND t2.id - t1.id = 321 */


For SQLite (the question is SQLite-tagged too)
UPDATE table
SET field1 = ( SELECT field1 
               FROM table t 
               WHERE t.id = 123 )
   /* or       WHERE t.id - table.id = 123     */
WHERE id = 456
/* or      WHERE id BETWEEN 444 AND 456        */