CREATE TABLE table_name_54 (built NUMBER, vessel_name VARCHAR2, class VARCHAR2, type VARCHAR2)

Which year was the vessel Deva built as a Panamax DNV class ship?
SELECT SUM(built) FROM table_name_54 WHERE class = "dnv" AND type = "panamax" AND vessel_name = "deva"
SELECT SUM("built") FROM "table_name_54" WHERE "class" = "dnv" AND "deva" = "vessel_name" AND "panamax" = "type"