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Code Lab is in development. New lessons and improvements are on the way. Progress can be deleted.
SQL / POSTGRESQL / Learn / LESSON 04
A foreign key links a child row to a parent. One author has many books (1:N). authors already exists — create books with author_id REFERENCES authors(id) and insert a valid row.
Small example:
CREATE TABLE books ( id INTEGER PRIMARY KEY, title TEXT NOT NULL, author_id INTEGER NOT NULL REFERENCES authors(id) ); INSERT INTO books (id, title, author_id) VALUES (1, 'Notes', 1);
Starting tables for this task. Grading checks final state on other datasets too.
| id | name |
|---|---|
| 1 | Ada |
| 2 | Grace |
Expected verify columns: column_name, id, title, author_id · row order is checked
Expected final state (displayed data):
Loading…A foreign key links a child row to a parent. One author has many books (1:N). authors already exists — create books with author_id REFERENCES authors(id) and insert a valid row.
QUERY STANDBY
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