Извлечете годината от датата и групирайте по нея
select year(date) as year,
count(customer_id) as customers
from your_table
group by year
order by year asc
Извлечете годината от датата и групирайте по нея
select year(date) as year,
count(customer_id) as customers
from your_table
group by year
order by year asc