Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Staff ( staff_id VARCHAR, first_name VARCHAR, last_name VARCHAR )
TABLE: CREATE TABLE Lessons ( staff_id VARCHAR )

### Question ###
How long is the total lesson time taught by staff with first name as Janessa and last name as Sawayn?

### Accurate SQL ###

SELECT SUM(lesson_time) FROM Lessons AS T1 JOIN Staff AS T2 ON T1.staff_id = T2.staff_id WHERE T2.first_name = "Janessa" AND T2.last_name = "Sawayn"