user: Question: What is the opening date of the Musical at the Adelphi Theatre?
Columns: ['Theatre', 'Current show', 'Classification', 'Capacity', 'Opening date', 'Closing date']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Adelphi Theatre', 'The Bodyguard', 'Musical', 1500.0, '2012-12-05 5 December 2012', 'Open-ended']
SQL:

assistant: SELECT "Opening date" FROM "Table" WHERE "Classification" = 'Musical' AND "Theatre" = 'Adelphi Theatre';