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_93 ( opponent VARCHAR, date VARCHAR, championship VARCHAR, surface VARCHAR, outcome VARCHAR )

### Question ###
who is the opponent when the surface is clay, the outcome is winner and the championship is estoril on 15 april 1996?

### Accurate SQL ###

SELECT opponent FROM table_name_93 WHERE surface = "clay" AND outcome = "winner" AND championship = "estoril" AND date = "15 april 1996"