CREATE TABLE table_203_547 (id NUMBER, "ship" CLOB, "built" NUMBER, "in service for cunard" CLOB, "type" CLOB, "tonnage" CLOB, "notes" CLOB)

what is the difference in the tonage between the queen mary and media ?
SELECT (SELECT "tonnage" FROM table_203_547 WHERE "ship" = 'queen mary') - (SELECT "tonnage" FROM table_203_547 WHERE "ship" = 'media')
SELECT (SELECT "tonnage" FROM "table_203_547" WHERE "ship" = 'queen mary') - (SELECT "tonnage" FROM "table_203_547" WHERE "ship" = 'media')