CREATE TABLE "u_bahn_network" (
  "line" text,
  "colour" text,
  "route" text,
  "length" text,
  "stations" real
);

Question: What is the total number of stations with a line that is u 6?
SQL: SELECT SUM("stations") FROM "u_bahn_network" WHERE "line"='u 6';

Question: Which route has 21 stations?
SQL: SELECT "route" FROM "u_bahn_network" WHERE "stations"=21;

Question: Which line was green?
SQL: SELECT "line" FROM "u_bahn_network" WHERE "colour"='green';