Table: submarine_history
Columns: shipyard
laid_down
launched
commissioned
fleet
status

Question: Which fleet launched on July 30, 1961?
SQL: SELECT "fleet" FROM submarine_history WHERE "launched" = 'july 30, 1961'

Question: Which shipyard has a fleet that was laid down on April 21, 1962?
SQL: SELECT "shipyard" FROM submarine_history WHERE "laid_down" = 'april 21, 1962'

Question: What is the status of the fleet that was commissioned on July 28, 1963?
SQL: SELECT "status" FROM submarine_history WHERE "commissioned" = 'july 28, 1963'