user: ### NOW ANSWER:
Question: When did Northeastern University join?
Columns: ['Institution', 'Location', 'Founded', 'Type', 'Joined', 'Nickname', 'Colors']
Types: ['text', 'text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['Boston University', 'Boston, MA', 1839.0, 'Private', 1973.0, 'Terriers', 'Scarlet & White']
SQL:

assistant: SELECT SUM("Joined") FROM "Table" WHERE "Institution" = 'Northeastern University';