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_23958944_2 (written_by VARCHAR, no_by_series VARCHAR)

### Question ###
How many different writers have written the episode with series number 8?

### Accurate SQL ###

SELECT COUNT(written_by) FROM table_23958944_2 WHERE no_by_series = 8