CREATE TABLE church (church_id NUMBER, name CLOB, organized_by CLOB, open_date NUMBER, continuation_of CLOB)
CREATE TABLE people (people_id NUMBER, name CLOB, country CLOB, is_male CLOB, age NUMBER)
CREATE TABLE wedding (church_id NUMBER, male_id NUMBER, female_id NUMBER, year NUMBER)

Show the opening year in whcih at least two churches opened.
SELECT open_date FROM church GROUP BY open_date HAVING COUNT(*) >= 2
SELECT "open_date" FROM "church" GROUP BY "open_date" HAVING COUNT(*) >= 2