Table: tennis_match_results_26
Columns: outcome
date
surface
opponent
score

Question: What is the score when Li Na was the opponent?
SQL: SELECT "score" FROM tennis_match_results_26 WHERE "opponent" = 'li na'

Question: Who was the opponent on 19 February 2011?
SQL: SELECT "opponent" FROM tennis_match_results_26 WHERE "date" = '19 february 2011'