Question: How about the number of projects they worked before 1989-04-24 23:51:54'? | The total number of distinct projects that have some project staffs worked as a leader and worked before 1989-04-24 23:51:54' is 2 | What are other detail about those projects?
SQL: SELECT other_details FROM Project_Staff WHERE role_code   =   'leader' and date_from  <  '1989-04-24 23:51:54'