Table: miguel_malvar_corvette
Columns: bow_number
ship_name
launched
commissioned
service

Question: When did the ship commissioned in November 1975 with a bow number of ps-18 launch?
SQL: SELECT "launched" FROM miguel_malvar_corvette 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 miguel_malvar_corvette WHERE "commissioned" = 'july 1948' AND "bow_number" = 'ps-31'

Question: When was the ship BRP Miguel Malvar commissioned?
SQL: SELECT "commissioned" FROM miguel_malvar_corvette WHERE "ship_name" = 'brp miguel malvar'