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_36 (championship VARCHAR, year VARCHAR, opponent VARCHAR, surface VARCHAR)

### Question ###
Which championship has Roger Federer as an opponent on a clay surface in a year earlier than 2007?

### Accurate SQL ###

SELECT championship FROM table_name_36 WHERE opponent = "roger federer" AND surface = "clay" AND year < 2007