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)
CREATE TABLE manager (manager_id NUMBER, name CLOB, country CLOB, working_year_starts CLOB, age NUMBER, level NUMBER)

Show the distinct countries of managers.
SELECT DISTINCT country FROM manager
SELECT DISTINCT "country" FROM "manager"