Table: hull_trains_170
Columns: class
type
built
number
withdrawn

Question: Which class had a number under 4 and was built in 1988?
SQL: SELECT "class" FROM hull_trains_170 WHERE "number" < 4 AND "built" = '1988'

Question: How many items withdrawn had numbers over 5?
SQL: SELECT COUNT("withdrawn") FROM hull_trains_170 WHERE "number" > 5

Question: What is the sum of numbers that had a type of Driving Van Trailer?
SQL: SELECT SUM("number") FROM hull_trains_170 WHERE "type" = 'driving van trailer'