Table: chelsea_season_1998
Columns: date
round
opponent
venue
result
attendance

Question: What is the average Attendance, when Date is 1 October 1998?
SQL: SELECT AVG("attendance") FROM chelsea_season_1998 WHERE "date" = '1 october 1998'

Question: What is Opponent, when Date is 17 September 1998?
SQL: SELECT "opponent" FROM chelsea_season_1998 WHERE "date" = '17 september 1998'

Question: What is Opponent, when Date is 8 April 1999?
SQL: SELECT "opponent" FROM chelsea_season_1998 WHERE "date" = '8 april 1999'