Join Clauses

Imagine you have two toy boxes: 🟦 One box has LEGO people (names & ages). 🟥 Another box has their favorite toys (name & toy).

But you want to know which person likes which toy!

A JOIN in SQL helps you combine these two boxes based on something common—like the person’s name. So, a JOIN clause is used to combine rows from two or more tables, based on a related column between them. A JOIN is also considered an inner join by default.

Example

Two Tables:

🔹 People Table:

Name	Age
Alice	5
Bob	6
Charlie	4

🔹 Toys Table:

Name	Favorite Toy
Alice	Teddy Bear
Bob	Toy Car

Using JOIN to Connect the Two

SELECT People.Name, People.Age, Toys.Favorite_Toy
FROM People
JOIN Toys ON People.Name = Toys.Name;

Result:

Name	Age	Favorite Toy
Alice	5	Teddy Bear
Bob	6	Toy Car

Now we can see who loves which toy!

Types of JOINs with the same analogy

1️⃣ INNER JOIN - Only keeps matching names from both boxes 2️⃣ LEFT JOIN - Keeps everyone from People, even if they don’t have a toy 3️⃣ RIGHT JOIN - Keeps all toys, even if no person is found 4️⃣ FULL JOIN - Keeps everything, even if they don’t match)