* Table Name: `customers`
* Columns:
* `customer_id`: Primary key, auto-incrementing integer.
* `first_name`: Customer's first name, string.
* `last_name`: Customer's last name, string.
* `email`: Customer's email address, string.
* `phone`: Customer's phone number, string.
* `address`: Customer's street address, string.
* `city`: Customer's city, string.
* `state`: Customer's state (2-letter abbreviation), string.
* `zip`: Customer's zip code, string.
* Constraints:
* `PRIMARY KEY (customer_id)`: Enforces the uniqueness of customer IDs.
* `UNIQUE (email)`: Enforces the uniqueness of customer email addresses.
