Table joins

Table joins are used to combine data from more than one table based on certain conditions on a certain column or columns.

For example, let's assume the following two tables exist:

CREATE TABLE customers (
    id UUID PRIMARY KEY,
    name STRING NOT NULL
);
CREATE TABLE purchase_orders (
     id UUID PRIMARY KEY,
     customer_id UUID, 
     n_of_items INT,
     total_price DECIMAL(10,2)
);

Now, let's look at each of the JOIN types with an example, as follows:

• INNER JOIN: Returns rows from the left and right operands that match the condition.

Let's look at the following example involving an inner join between the customers and purchase_orders tables:

SELECT a.id as customer_id, a.name AS customer_name, b.id AS purchase_order_id  FROM customers AS...