user: Question: In how many different years did schools located in Logan Township, Pennsylvania join the Conference?
Columns: ['Institution', 'Location', 'Nickname', 'Founded', 'Type', 'Enrollment', 'Joined']
Types: ['text', 'text', 'text', 'real', 'text', 'real', 'real']
Sample row: ["D'Youville College", 'Buffalo, New York', 'Spartans', 1946.0, 'Private/Catholic', 2900.0, 2009.0]
SQL:

assistant: SELECT COUNT("Joined") FROM "Table" WHERE "Location" = 'Logan Township, Pennsylvania';