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 table_name_19 ( points VARCHAR, wins VARCHAR, team VARCHAR, class VARCHAR, year VARCHAR )

### Question ###
How many points numbers had a class of 250cc, a year prior to 1978, Yamaha as a team, and where wins was more than 0?

### Accurate SQL ###

SELECT COUNT(points) FROM table_name_19 WHERE class = "250cc" AND year < 1978 AND team = "yamaha" AND wins > 0