Translate the following question to SQL: Find the number of customers in total.

Schema: CREATE TABLE Products (
    product_id INTEGER   PRIMARY KEY,
    product_name VARCHAR(20),
    product_price DECIMAL(19,4),
    product_description VARCHAR(255)
);

CREATE TABLE Addresses (
    address_id INTEGER   PRIMARY KEY,
    address_details VARCHAR(80),
    city VARCHAR(50),
    zip_postcode VARCHAR(20),
    state_province_county VARCHAR(50),
    country VARCHAR(50)
);

CREATE TABLE Customers (
    customer_id INTEGER   PRIMARY KEY,
    payment_method VARCHAR(10) NOT NULL,
    customer_name VARCHAR(80),
    customer_phone VARCHAR(80),
    customer_email VARCHAR(80),
    date_became_customer DATETIME
);

CREATE TABLE Regular_Orders (
    regular_order_id INTEGER   PRIMARY KEY,
    distributer_id INTEGER NOT NULL,
    FOREIGN KEY (distributer_id) REFERENCES Customers(customer_id)
);

CREATE TABLE Regular_Order_Products (
    regular_order_id INTEGER NOT NULL,
    product_id INTEGER NOT NULL,
    FOREIGN KEY (regular_order_id) REFERENCES Regular_Orders(regular_order_id),
    FOREIGN KEY (product_id) REFERENCES Products(product_id)
);

CREATE TABLE Actual_Orders (
    actual_order_id INTEGER   PRIMARY KEY,
    order_status_code VARCHAR(10) NOT NULL,
    regular_order_id INTEGER NOT NULL,
    actual_order_date DATETIME,
    FOREIGN KEY (regular_order_id) REFERENCES Regular_Orders(regular_order_id)
);

CREATE TABLE Actual_Order_Products (
    actual_order_id INTEGER NOT NULL,
    product_id INTEGER NOT NULL,
    FOREIGN KEY (actual_order_id) REFERENCES Actual_Orders(actual_order_id),
    FOREIGN KEY (product_id) REFERENCES Products(product_id)
);

CREATE TABLE Customer_Addresses (
    customer_id INTEGER NOT NULL,
    address_id INTEGER NOT NULL,
    date_from DATETIME NOT NULL,
    address_type VARCHAR(10) NOT NULL,
    date_to DATETIME,
    FOREIGN KEY (address_id) REFERENCES Addresses(address_id),
    FOREIGN KEY (customer_id) REFERENCES Customers(customer_id)
);

CREATE TABLE Delivery_Routes (
    route_id INTEGER   PRIMARY KEY,
    route_name VARCHAR(50),
    other_route_details VARCHAR(255)
);

CREATE TABLE Delivery_Route_Locations (
    location_code VARCHAR(10)   PRIMARY KEY,
    route_id INTEGER NOT NULL,
    location_address_id INTEGER NOT NULL,
    location_name VARCHAR(50),
    UNIQUE (location_code),
    FOREIGN KEY (route_id) REFERENCES Delivery_Routes(route_id),
    FOREIGN KEY (location_address_id) REFERENCES Addresses(address_id)
);

CREATE TABLE Trucks (
    truck_id INTEGER   PRIMARY KEY,
    truck_licence_number VARCHAR(20),
    truck_details VARCHAR(255)
);

CREATE TABLE Employees (
    employee_id INTEGER   PRIMARY KEY,
    employee_address_id INTEGER NOT NULL,
    employee_name VARCHAR(80),
    employee_phone VARCHAR(80),
    FOREIGN KEY (employee_address_id) REFERENCES Addresses(address_id)
);

CREATE TABLE Order_Deliveries (
    location_code VARCHAR(10) NOT NULL,
    actual_order_id INTEGER NOT NULL,
    delivery_status_code VARCHAR(10) NOT NULL,
    driver_employee_id INTEGER NOT NULL,
    truck_id INTEGER NOT NULL,
    delivery_date DATETIME,
    FOREIGN KEY (driver_employee_id) REFERENCES Employees(employee_id),
    FOREIGN KEY (location_code) REFERENCES Delivery_Route_Locations(location_code),
    FOREIGN KEY (actual_order_id) REFERENCES Actual_Orders(actual_order_id),
    FOREIGN KEY (truck_id) REFERENCES Trucks(truck_id)
);
user
SELECT count(*) FROM customers
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