What is simple join?

A simple join returns elements from a primary collection that match any element in a secondary collection, based on a specified match condition. In essence, it's a way to filter the primary collection using the contents of the secondary collection.

Here's a breakdown of the concept:

• Primary Collection: The main dataset you're querying from.
• Secondary Collection: A supplementary dataset used for filtering.
• Match Condition: The criteria used to determine if an element from the primary collection has a corresponding element in the secondary collection.
• Result: The elements from the primary collection that satisfy the match condition when compared against the secondary collection.

Let's illustrate this with a simplified scenario:

Imagine you have two lists: a list of Customers and a list of Orders. You want to find all customers who have placed at least one order.

• Primary Collection: Customers (containing customer information like ID, name, etc.)
• Secondary Collection: Orders (containing order information including customer ID)
• Match Condition: Customer.ID is present in the Orders.CustomerID
• Result: A list of Customers who have a corresponding entry in the Orders list.

In other words, the simple join acts like a filter, returning only the Customers for whom at least one matching Order exists.