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CREATE TABLE Author (code VARCHAR(2), Name VARCHAR(9)); INSERT INTO Author (code, Name) VALUES ('GB', 'George B.'), ('KL', 'Kyle L.'), ('DC', 'Donald C.'), ('RL', 'Roland L.'); CREATE TABLE Book (isbn INTEGER, author VARCHAR(2)); INSERT INTO Book (isbn, author) VALUES ('1111', 'GB'), ('2222', 'DC'), ('3333', 'RL'); CREATE TABLE Coauthor (name VARCHAR(2), isbn INTEGER); INSERT INTO Coauthor (name, isbn) VALUES ('KL', '1111'), ('GB', '2222'), ('GB', '3333');
SELECT a.code, a.name, COUNT(DISTINCT b.isbn) + COUNT(DISTINCT c.isbn) count FROM Author a LEFT JOIN Book b ON b.author = a.code LEFT JOIN Coauthor c ON c.name = a.code GROUP BY a.code, a.name;
code
name
count
DC
Donald C.
1
GB
George B.
3
KL
Kyle L.
1
RL
Roland L.
1