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

How many churches have a wedding in year 2016?
SELECT COUNT(DISTINCT church_id) FROM wedding WHERE year = 2016
SELECT COUNT(DISTINCT "church_id") FROM "wedding" WHERE "year" = 2016