"""
Following is the database schema.

DROP TABLE IF EXISTS product_categories;
CREATE TABLE IF NOT EXISTS product_categories
(
    category_id INTEGER PRIMARY KEY, -- Unique ID for each category
    name        VARCHAR(50),         -- Name of the category
    parent      INTEGER NULL,        -- Parent category - for hierarchical categories
    FOREIGN KEY (parent) REFERENCES product_categories (category_id)
);
DROP TABLE IF EXISTS products;
CREATE TABLE IF NOT EXISTS products
(
    product_id  INTEGER PRIMARY KEY, -- Unique ID for each product
    name        VARCHAR(50),         -- Name of the product
    price       DECIMAL(10, 2),      -- Price of each unit of the product
    quantity    INTEGER,             -- Current quantity in stock
    category_id INTEGER,             -- Unique ID for each product
    FOREIGN KEY (category_id) REFERENCES product_categories (category_id)
);
DROP TABLE IF EXISTS customers;
CREATE TABLE IF NOT EXISTS customers
(
    customer_id INTEGER PRIMARY KEY, -- Unique ID for each customer
    name        VARCHAR(50),         -- Name of the customer
    address     VARCHAR(100)         -- Mailing address of the customer
);
DROP TABLE IF EXISTS salespeople;
CREATE TABLE IF NOT EXISTS salespeople
(
    salesperson_id INTEGER PRIMARY KEY, -- Unique ID for each salesperson
    name           VARCHAR(50),         -- Name of the salesperson
    region         VARCHAR(50)          -- Geographic sales region
);
DROP TABLE IF EXISTS sales;
CREATE TABLE IF NOT EXISTS sales
(
    sale_id        INTEGER PRIMARY KEY, -- Unique ID for each sale
    product_id     INTEGER,             -- ID of product sold
    customer_id    INTEGER,             -- ID of customer who made the purchase
    salesperson_id INTEGER,             -- ID of salesperson who made the sale
    sale_date      DATE,                -- Date the sale occurred
    quantity       INTEGER,             -- Quantity of product sold
    FOREIGN KEY (product_id) REFERENCES products (product_id),
    FOREIGN KEY (customer_id) REFERENCES customers (customer_id),
    FOREIGN KEY (salesperson_id) REFERENCES salespeople (salesperson_id)
);
DROP TABLE IF EXISTS product_suppliers;
CREATE TABLE IF NOT EXISTS product_suppliers
(
    supplier_id  INTEGER PRIMARY KEY, -- Unique ID for each supplier
    product_id   INTEGER,             -- Product ID supplied
    supply_price DECIMAL(10, 2),      -- Unit price charged by supplier
    FOREIGN KEY (product_id) REFERENCES products (product_id)
);


Generate only a valid (syntactically correct) executable Postgres SQL query (without any explanation of the query) for the following question:
`<question>`:
"""