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

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"