Table: chelsea_season
Columns: date
round
opponent
venue
result
attendance

Question: What is the round of the match at venue A with a result of 1-2 on 7 December 2004?
SQL: SELECT "round" FROM chelsea_season WHERE "venue" = 'a' AND "result" = '1-2' AND "date" = '7 december 2004'

Question: Who was the opponent of the match in round sf with a result of 0-0?
SQL: SELECT "opponent" FROM chelsea_season WHERE "round" = 'sf' AND "result" = '0-0'