How to use views argument in drupal?
If this is a contextual filter, you can specify AND or OR logic for the multi-values.

Views says:


  Allow multiple values
  
  If selected, users can enter multiple values in the form of 1+2+3 (for
  OR) or 1,2,3 (for AND).


So your querstring would have &amp;state=CA+NY+TX to OR California, New York, and Texas states.