Master SQL JOINs: Learn About Different Types of JOINs in SQL

If you're working with relational databases, it's essential to understand SQL JOINs. JOINs allow you to combine data from multiple tables into a single result set. In this article, we'll explore the different types of JOINs in SQL and how to use them effectively.

├Źndice
  1. Inner Join
  2. Left Join
  3. Right Join
  4. Full Outer Join
  5. Cross Join

Inner Join

The INNER JOIN is the most commonly used JOIN in SQL. It returns only the rows that have matching values in both tables being joined. To perform an INNER JOIN, you need to specify the common column(s) between the tables using the ON keyword. For example:


SELECT *
FROM table1
INNER JOIN table2
ON table1.common_column = table2.common_column;

Left Join

The LEFT JOIN returns all the rows from the left table and the matching rows from the right table. If there are no matching rows in the right table, the result set will contain NULL values for the right table's columns. Here's an example:


SELECT *
FROM table1
LEFT JOIN table2
ON table1.common_column = table2.common_column;

Right Join

The RIGHT JOIN is the opposite of the LEFT JOIN. It returns all the rows from the right table and the matching rows from the left table. If there are no matching rows in the left table, the result set will contain NULL values for the left table's columns. Here's an example:


SELECT *
FROM table1
RIGHT JOIN table2
ON table1.common_column = table2.common_column;

Full Outer Join

The FULL OUTER JOIN returns all the rows from both tables, including the non-matching rows. If there are no matching rows in one of the tables, the result set will contain NULL values for the corresponding columns. Here's an example:


SELECT *
FROM table1
FULL OUTER JOIN table2
ON table1.common_column = table2.common_column;

Cross Join

The CROSS JOIN returns the Cartesian product of the two tables. In other words, it returns all possible combinations of rows from both tables. This type of join is used when you need to join every row in one table with every row in another table. Here's an example:


SELECT *
FROM table1
CROSS JOIN table2;

By understanding the different types of SQL JOINs and how to use them, you can write more complex queries and extract valuable insights from your data. Whether you're a beginner or an experienced SQL programmer, mastering JOINs is an essential skill for working with relational databases.

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