Primary key from multiple columns
CREATE TABLE world (
country TEXT NOT NULL,
state TEXT NOT NULL,
city TEXT NOT NULL,
population INTEGER NOT NULL,
PRIMARY KEY (country_id, state_id, city_id)
);
- All columns require a value when inserting.
- Two rows cannot have the same
country_id
,state_id
,city_id
combination. - Two or more rows can have the same values in two columns, with a different value in the third column.