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)
CREATE TABLE church (church_id NUMBER, name CLOB, organized_by CLOB, open_date NUMBER, continuation_of CLOB)

Show all opening years and the number of churches that opened in that year.
SELECT open_date, COUNT(*) FROM church GROUP BY open_date
SELECT "open_date", COUNT(*) FROM "church" GROUP BY "open_date"