SQL Refresher # 02

Problem : Show number of customers in each city

Solution :

SELECT count(*) , City from customers
GROUP BY city

Problem: Show only those cities with there customers counts where no of customers greater than 1

Solution :

SELECT count(*) , City from customers
GROUP BY city
HAVING count(*) > 1
Problem: Only select customers who made their orders

Solution #1

SELECT customers.first_name , customers.last_name
from Orders, customers
where orders.customer_id = customers.id

Solution #2

SELECT CONCAT(customers.first_name ,' ', customers.last_name) as CustomerName

from Orders, customers
where orders.customer_id = customers.id