图书馆想把从没被借过的书摆到显眼的地方。用 books LEFT JOIN loans，只留下找不到借书记录的书（loans.id 是空的），选出它们的 title。
| id | title | author | genre | pages | year |
|---|---|---|---|---|---|
| 1 | The Night Garden | Mia Lane | story | 210 | 2015 |
| 2 | Stars for Kids | Tom Hart | science | 96 | 2020 |
| 3 | Lost at Sea | Mia Lane | story | 340 | 2011 |
| 4 | Easy Bread | Rosa Bell | food | 128 | 2019 |
| 5 | The Bug Book | Tom Hart | science | 64 | 2022 |
| 6 | Soup Days | Rosa Bell | food | 150 | 2008 |
| 7 | The Red Kite | Ann Cole | story | 180 | 2021 |
| 8 | Rocks and Rivers | Ann Cole | science | 220 | 2017 |
| id | book_id | reader | days |
|---|---|---|---|
| 1 | 1 | Leo | 14 |
| 2 | 2 | Nora | 7 |
| 3 | 1 | Sam | NULL |
| 4 | 4 | Leo | 21 |
| 5 | 5 | Nora | NULL |
| 6 | 3 | Ivy | 10 |
| 7 | 2 | Sam | 5 |
| 8 | 7 | Ivy | 12 |
| id | title | author | genre | pages | year |
|---|---|---|---|---|---|
| 1 | The Night Garden | Mia Lane | story | 210 | 2015 |
| 2 | Stars for Kids | Tom Hart | science | 96 | 2020 |
| 3 | Lost at Sea | Mia Lane | story | 340 | 2011 |
| 4 | Easy Bread | Rosa Bell | food | 128 | 2019 |
| 5 | The Bug Book | Tom Hart | science | 64 | 2022 |
| 6 | Soup Days | Rosa Bell | food | 150 | 2008 |
| 7 | The Red Kite | Ann Cole | story | 180 | 2021 |
| 8 | Rocks and Rivers | Ann Cole | science | 220 | 2017 |
| id | book_id | reader | days |
|---|---|---|---|
| 1 | 1 | Leo | 14 |
| 2 | 2 | Nora | 7 |
| 3 | 1 | Sam | NULL |
| 4 | 4 | Leo | 21 |
| 5 | 5 | Nora | NULL |
| 6 | 3 | Ivy | 10 |
| 7 | 2 | Sam | 5 |
| 8 | 7 | Ivy | 12 |
SELECT books.title FROM books LEFT JOIN loans ON loans.book_id = books.id -- 在这里写：用 WHERE loans.id IS NULL 留下没配上的书 ;
写好了先点「运行」看看结果，没问题再点「提交」。