Table: kilo_submarine
Columns: operator
shipyard
project
commissioned
status

Question: What is the commissioned for Vietnam?
SQL: SELECT "commissioned" FROM kilo_submarine WHERE "operator" = 'vietnam'

Question: What is the commissioned with a 636.3 project, and ordered status?
SQL: SELECT "commissioned" FROM kilo_submarine WHERE "project" = '636.3' AND "status" = 'ordered'