The library wants to put the books nobody has borrowed somewhere easy to see. Do books LEFT JOIN loans, keep only the books with no loan (where loans.id is empty), and pick their title.
The tables
books
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
8 rows
loans
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
8 rows
books
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
8 rows
loans
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
8 rows
query.sql
SELECT books.title
FROM books
LEFT JOIN loans ON loans.book_id = books.id
-- your code here: WHERE loans.id IS NULL keeps the books with no match
;
Ctrl + Enter runs too
Result
Run shows what your query gives. When it looks right, Submit.