Table: gb_railfreight_rolling_stock
Columns: class
type
introduced
fleet_size
numbers

Question: What is the fleet size of the Vanguard 0-6-0dh class?
SQL: SELECT "fleet_size" FROM gb_railfreight_rolling_stock WHERE "class" = 'vanguard 0-6-0dh'

Question: What is the year of introduction for the Electro-Diesel locomotive?
SQL: SELECT "introduced" FROM gb_railfreight_rolling_stock WHERE "type" = 'electro-diesel locomotive'

Question: What is the average fleet size for the Shunter type introduced in 1959?
SQL: SELECT AVG("fleet_size") FROM gb_railfreight_rolling_stock WHERE "type" = 'shunter' AND "introduced" = '1959'

Question: What is the smallest fleet size with a type of shunter introduced in 1953?
SQL: SELECT MIN("fleet_size") FROM gb_railfreight_rolling_stock WHERE "type" = 'shunter' AND "introduced" = '1953'