In the loans table, the number of days (days) is only filled in once a book comes back; for books still out, days is empty. Count how many loans have a value in days.
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
-- your code here: put days inside COUNT instead of *
SELECT COUNT(*)
FROM loans;
Ctrl + Enter runs too
Result
Run shows what your query gives. When it looks right, Submit.