CREATE TABLE bridge (architect_id NUMBER, id NUMBER, name CLOB, location CLOB, length_meters NUMBER, length_feet NUMBER)
CREATE TABLE mill (architect_id NUMBER, id NUMBER, location CLOB, name CLOB, type CLOB, built_year NUMBER, notes CLOB)
CREATE TABLE architect (id CLOB, name CLOB, nationality CLOB, gender CLOB)

What is the average length in feet of the bridges?
SELECT AVG(length_feet) FROM bridge
SELECT AVG("length_feet") FROM "bridge"