SELECT * FROM book JOIN borrow USING (book_id);
SELECT * FROM book JOIN borrow WHERE book.book_id = borrow.book_id;
這兩條SQL語句等價(但第二條語句會查出兩個book_id列)
故簡而言之USING()函數的作用是簡化等值連接語句.
SELECT * FROM book JOIN borrow USING (book_id);
SELECT * FROM book JOIN borrow WHERE book.book_id = borrow.book_id;
這兩條SQL語句等價(但第二條語句會查出兩個book_id列)
故簡而言之USING()函數的作用是簡化等值連接語句.