user: Question: Which opponent has a date 21 Jul 2007?
Columns: ['Match', 'Date', 'Competition or tour', 'Ground', 'Opponent', 'Score1']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '14 Jul 2007', '—', 'A', 'Dagenham & Redbridge', '2 - 0']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = '21 Jul 2007';