user: Question: Which Established has a League of Ontario Australian Football League?
Columns: ['Club', 'League', 'Sport', 'Established', 'Championships']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['Guelph Storm', 'Ontario Hockey League', 'Hockey', '1991', 2.0]
SQL:

assistant: SELECT "Established" FROM "Table" WHERE "League" = 'Ontario Australian Football League';