CREATE TABLE manager (manager_id NUMBER, name CLOB, country CLOB, working_year_starts CLOB, age NUMBER, level NUMBER)
CREATE TABLE railway_manage (railway_id NUMBER, manager_id NUMBER, from_year CLOB)
CREATE TABLE railway (railway_id NUMBER, railway CLOB, builder CLOB, built CLOB, wheels CLOB, location CLOB, objectnumber CLOB)
CREATE TABLE train (train_id NUMBER, train_num CLOB, name CLOB, from CLOB, arrival CLOB, railway_id NUMBER)

Show the id and builder of the railway that are associated with the most trains.
SELECT T2.railway_id, T1.builder FROM railway AS T1 JOIN train AS T2 ON T1.railway_id = T2.railway_id GROUP BY T2.railway_id ORDER BY COUNT(*) DESC LIMIT 1
SELECT "T2"."railway_id", "T1"."builder" FROM "railway" "T1" JOIN "train" "T2" ON "T1"."railway_id" = "T2"."railway_id" GROUP BY "T2"."railway_id" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY