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_23 ( partner VARCHAR, surface VARCHAR, date VARCHAR )

### Question ###
What is the name of a partner that played on a hard surface on 18 April 2011?

### Accurate SQL ###

SELECT partner FROM table_name_23 WHERE surface = "hard" AND date = "18 april 2011"