user: Question: what is the launched date when the builder is John Brown, Clydebank?
Columns: ['Name', 'Pennant', 'Builder', 'Laid Down', 'Launched', 'Commissioned']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Caprice (ex-Swallow)', 'R01 later D01', 'Yarrow , Scotstoun', '24 September 1942', '16 September 1943', '5 April 1944']
SQL:

assistant: SELECT "Launched" FROM "Table" WHERE "Builder" = 'John Brown, Clydebank';