Hi,

I've a self-join with only inequalities (< and >)

select a.name, a.salary, b.name, b.salary
  from salary_tax a
     , salary_tax b
 where a.salary > b.salary
   and a.tax < b.tax

on a simple table like this

CREATE TABLE salary_tax (
  name character varying(255) NOT NULL,
  dept character varying(50),
  salary integer,
  tax integer)

All the DBMSs I tried are doing a Cartesian product followed by selection which is very expensive any idea on how to do it better?

I was thinking about using a variant of sort-merge join?