Question: What is the date when tie number is 6?
SQL: SELECT "Date" FROM "2-17520911-5" WHERE "Tie no" = '6';

Question: Who is the home team with tie number 9?
SQL: SELECT "Home team" FROM "2-17520911-5" WHERE "Tie no" = '9';

Question: Who is the home team when Sheffield United is the away team?
SQL: SELECT "Home team" FROM "2-17520911-5" WHERE "Away team" = 'Sheffield United';

Question: What is the date when Aston Villa is the away team?
SQL: SELECT "Date" FROM "2-17520911-5" WHERE "Away team" = 'Aston Villa';

Question: Who is the home team on 31 January 1951 when away team was Sheffield United?
SQL: SELECT "Home team" FROM "2-17520911-5" WHERE "Date" = '31 January 1951' AND "Away team" = 'Sheffield United';