Unique Customer Cities

Problem Statement

Problem Description Write a SQL query to retrieve a list of all unique cities where customers reside based on the provided customer table. Schema The customer table contains the following columns: customer_id (INTEGER): The unique identifier for the customer. firstname (VARCHAR): The customer's first name. lastname (VARCHAR): The customer's last name. birth_date (DATE): The customer's date of birth. address (VARCHAR): The customer's street address. zipcode (VARCHAR): The postal code of the customer's address. city (VARCHAR): The city where the customer resides. phone_number (VARCHAR): The customer's phone number. Required Output The query must return a result set adhering to the following requirements: The output must contain a single column named CITY . The result must contain no duplicate city names. The cities must be sorted alphabetically in ascending order. Constraints or Notes Any potential NULL values in the city column should be treated as a distinct unique value and ordered ac