user: Question: What is the sum of numbers that had a type of Driving Van Trailer?
Columns: ['Class', 'Type', 'Built', 'Number', 'Withdrawn']
Types: ['text', 'text', 'text', 'real', 'real']
Sample row: ['Class 170 Turbostar', 'diesel multiple unit', '1999–2004', 4.0, 2005.0]
SQL:

assistant: SELECT SUM("Number") FROM "Table" WHERE "Type" = 'Driving Van Trailer';