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 farm_competition ( Theme VARCHAR, YEAR VARCHAR )

### Question ###
What are the themes of farm competitions sorted by year in ascending order?

### Accurate SQL ###

SELECT Theme FROM farm_competition ORDER BY YEAR