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_2226817_4 ( written_by VARCHAR, original_air_date VARCHAR )

### Question ###
Name who wrote the episode that aired april 9, 1989

### Accurate SQL ###

SELECT written_by FROM table_2226817_4 WHERE original_air_date = "April 9, 1989"