How many project staff worked as leaders or started working before '1989-04-24 23:51:54'?
CREATE TABLE Project_Staff (
    role_code VARCHAR,
    date_from VARCHAR
)
SELECT COUNT(*) FROM Project_Staff WHERE role_code = 'leader' OR date_from < '1989-04-24 23:51:54'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many project staff worked as leaders or started working before '1989-04-24 23:51:54'? ### Input: CREATE TABLE Project_Staff (
    role_code VARCHAR,
    date_from VARCHAR
) ### Response: SELECT COUNT(*) FROM Project_Staff WHERE role_code = 'leader' OR date_from < '1989-04-24 23:51:54'