DELETE table1
FROM
 table1, 
 (
  SELECT
   min(primary_key) id,
   <filter_a>,
   <filter_b>
  FROM
   <table_name>
  GROUP BY
   <filter_a>,
   <filter_b>
  HAVING
   count(*) > 1
 ) table2
WHERE
 table1.filter_a = table2.filter_a
 and table1.filter_b = table2.filter_b
AND table1.primary_key > table2.primary_key;