MySQL error #1111 - Invalid use of group function - mysql

Question

Yes, this is an assignment. So the task was to output two columns of 'first name' and 'last name' with conditions:
-A u (B ∩ -C ∩ -(A ∩ -( B u D)))
A: All consumers that didn't shop on Monday and Friday
(time_by_day.the_day)
B: All consumers who bought 'Non-Consumable'
(product_class.product_family)
C: All consumers who bought more than 10 items
(sales_fact_1997.unit_sales) at one time (sales_fact_1997.time_id)
D: Female consumers from Canada (consumer.gender, consumer.country)
This is what I got so far
SELECT
c.fname,
c.lname
FROM
customer AS c
INNER JOIN sales_fact_1997 AS s ON c.customer_id = s.customer_id
INNER JOIN time_by_day AS t ON s.time_id = t.time_id
INNER JOIN product AS p ON s.product_id = p.product_id
INNER JOIN product_class AS pc ON p.product_class_id = pc.product_class_id
Where
NOT t.the_day in ('Monday', 'Friday') OR
(
pc.product_family = 'Non-Consumable' AND
NOT SUM(s.unit_sales) > 10 AND
NOT (
t.the_day in ('Monday', 'Friday') AND
NOT (
pc.product_family = 'Non-Consumable' OR
(c.country = 'Canada' AND c.gender = 'F')
)
)
)
GROUP BY concat(c.customer_id, s.time_id)
That ended up with an error
#1111 - Invalid use of group function
But I don't know which part of the code is wrong. I'm pretty sure that it's probably the WHERE part. But I don't know what I did wrong.
Condition C is where I'm really struggling. I manage just fine making a query of C
SELECT
t.time_id,
c.customer_id,
c.fullname,
round(SUM(s.unit_sales),0) as tot
FROM
customer as c
INNER JOIN sales_fact_1997 as s ON c.customer_id = s.customer_id
INNER JOIN time_by_day as t on s.time_id=t.time_id
GROUP BY concat(c.customer_id, s.time_id)
ORDER BY c.customer_id, t.time_id
But trying to incorporate it into the main code is hard for me.
Reading online I assume that I should probably use HAVING instead of WHERE.
I would really appreciate it if someone can point me in the right direction.
This is the database that I used.

Answer 1

C: All consumers who bought more than 10 items
(sales_fact_1997.unit_sales) at one time (sales_fact_1997.time_id)
You should use COUNT not SUM.
SELECT time_id,
count(*)
FROM sales_fact_1997
GROUP BY time_id
HAVING COUNT(*)>=10 ;
count(*) is not needed, I let just to show the results
Can you try if it helps:
SELECT c.lname,
c.fname
FROM customer c
INNER JOIN
(
SELECT time_id,customer_id,product_id
FROM sales_fact_1997
GROUP BY time_id,customer_id,product_id
HAVING COUNT(*)>=10
) as s on c.customer_id=s.customer_id
INNER JOIN
(
SELECT time_id,the_day
FROM time_by_day
WHERE the_day
NOT IN ('Monday','Friday')
) as t on s.time_id=t.time_id
INNER JOIN
(
SELECT product_family,product_id
FROM product_class
INNER JOIN product
on product_class.product_class_id=product.product_class_id
WHERE product_family='Non-Consumable'
) pc on s.product_id=pc.product_id
where c.country='Canada' and c.gender ='F' ;