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_6 ( opening_date VARCHAR, classification VARCHAR, theatre VARCHAR )

### Question ###
What is the opening date of the musical at the adelphi theatre?

### Accurate SQL ###

SELECT opening_date FROM table_name_6 WHERE classification = "musical" AND theatre = "adelphi theatre"