SPARQL Questions

Dear all

1) Can you provide me examples of two SPARQL queries which are equivalent,
SELECT or ASK query
2) Please also provide me an example of a query which has no solution,
SELECT or ASK query
3) Do you think embedding SPARQL in a logic and getting to see if two
queries are contained (containment between queries),
equivalent, satisfiable, and so on is of great importance?

Thank you for taking your time to respond to these questions.

kind regards
-Mel