CREATE TABLE ship (TYPE VARCHAR, Tonnage INT)

Show the types of ships that have both ships with tonnage larger than 6000 and ships with tonnage smaller than 4000.
SELECT TYPE FROM ship WHERE Tonnage > 6000 INTERSECT SELECT TYPE FROM ship WHERE Tonnage < 4000
SELECT "TYPE" FROM "ship" WHERE "Tonnage" > 6000 INTERSECT SELECT "TYPE" FROM "ship" WHERE "Tonnage" < 4000