Day 22 of My Data Analytics Journey !

Today I explored SQL Joins – one of the most important concepts in relational databases and also practiced with some coding problems on HackerRank.

Types of Joins

1. INNER JOIN → Returns only the matching rows from both tables.
2. LEFT JOIN → Returns all rows from the left table + matched rows from the right table.
3. RIGHT JOIN → Returns all rows from the right table + matched rows from the left table.
4. FULL JOIN (or OUTER JOIN) → Returns all rows when there is a match in one of the tables.

Among these, the most commonly used is the INNER JOIN.

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✅ INNER JOIN Example

Let’s say we have two tables:

movies

movie_id	movie_name
1	Ghajini
2	Singam
3	Kaakha Kaakha

actors

actor_id	actor_name
1	Surya
2	Asin
3	Jyothika

movie_actors

movie_id	actor_id
1	1
1	2
3	1
3	3

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📝 Query (INNER JOIN)

SELECT m.movie_name, a.actor_name
FROM movies m
INNER JOIN movie_actors ma ON m.movie_id = ma.movie_id
INNER JOIN actors a ON ma.actor_id = a.actor_id;

Output

movie_name	actor_name
Ghajini	Surya
Ghajini	Asin
Kaakha Kaakha	Surya
Kaakha Kaakha	Jyothika