CREATE TABLE table_47079 ("Name" TEXT, "Class" TEXT, "Navy" TEXT, "Date joined" TEXT, "Date departed" TEXT)

What's the departed date that the HMS Leith of the Royal Navy?
SELECT "Date departed" FROM table_47079 WHERE "Navy" = 'royal navy' AND "Name" = 'hms leith'
SELECT "Date departed" FROM "table_47079" WHERE "Name" = 'hms leith' AND "Navy" = 'royal navy'