country builder location ship class / type
country
builder
location
ship
class \\/ type
number parsed year month day
address
date text text address text text
6 march united states john roach and son chester, pennsylvania city of rio de janeiro passenger ship
count how many different classes of ships were launched .
NN WRB JJ JJ NNS IN NNS VBD-AUX VBN .
4
select count ( distinct c6 ) from w