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_203_17 ( id number, "name" text, "date of death" text, "ceremony" text, "year" text, "academy award" text, "film" text, "winner" text )

### Question ###
how many years are listed for howard ashman under the year column ?

### Accurate SQL ###

SELECT COUNT(DISTINCT "year") FROM table_203_17 WHERE "name" = 'howard ashman'