What column(s) may contain NULL values?
CREATE TABLE impression(
banner_id INTEGER NOT NULL,
is_click BOOLEAN NOT NULL,
user_id VARCHAR(100),
geo VARCHAR(3),
site_id INTEGER NOT NULL);What column(s) may contain NULL values?
CREATE TABLE impression(
banner_id INTEGER NOT NULL,
is_click BOOLEAN NOT NULL,
user_id VARCHAR(100),
geo VARCHAR(3),
site_id INTEGER NOT NULL);Create a free account to access the full topic