SELECT TITEM1.item_number AS item1, 
  TITEM1.item_descrip1 AS item1_descrip,
  TITEM2.item_number AS item2, 
  TITEM2.item_descrip1 AS item2_descrip,
  TITEM2.item_descrip2 AS item2_spec
FROM mpe.hwcompatibilitypairs 
JOIN item AS TITEM1 ON hwcompatibilitypairs_item1_id = TITEM1.item_id 
JOIN item AS TITEM2 ON hwcompatibilitypairs_item2_id = TITEM2.item_id