(a) 
SELECT * FROM homes WHERE
  price > 140000 AND price < 150000

(b)
SELECT * FROM homes WHERE
  longitude > 122.3 AND longitude < 122.4
  AND latitude > 37.5 AND latitude < 37.6

Example 1: Two queries. (a) One-dimensional query handled efficiently by B-tree; (b) two-dimensional query is less efficient.