Question: When did the ship commissioned in November 1975 with a bow number of PS-18 launch?
SQL: SELECT "Launched" FROM "2-17849650-1" WHERE "Commissioned" = 'November 1975' AND "Bow number" = 'PS-18';

Question: When did the ship that was commissioned July 1948 with a bow number of PS-31 launch?
SQL: SELECT "Launched" FROM "2-17849650-1" WHERE "Commissioned" = 'July 1948' AND "Bow number" = 'PS-31';

Question: When was the ship BRP Miguel Malvar commissioned?
SQL: SELECT "Commissioned" FROM "2-17849650-1" WHERE "Ship name" = 'BRP Miguel Malvar';