Natural Join - (MySQL Join)

In MySQL, a natural join is a type of join that allows you to combine two or more tables based on their columns having matching names and data types. In this tutorial, we'll go over the syntax, examples, and uses of natural join in MySQL.

Syntax

The basic syntax for a natural join is as follows:

SELECT column_name(s)
FROM table1
NATURAL JOIN table2;

Here, the "SELECT column_name(s)" specifies the columns you want to display in the output. "table1" and "table2" are the names of the tables you want to join.

Example

Let's say we have two tables called "employees" and "departments". The "employees" table has a column called "dept_id", and the "departments" table has a column called "id", which provides the department ID.

We can use the natural join to combine these tables as follows:

SELECT *
FROM employees
NATURAL JOIN departments;

This will return a result set that includes all columns from both tables where the "dept_id" column in "employees" matches the "id" column in "departments".

Output

The output of the example above might look like this:

+------+-------+------+--------+------------+--------+
| id   | name  | age  | salary | dept_id    | name   |
+------+-------+------+--------+------------+--------+
| 1    | John  | 30   | 5000   | 100        | IT     |
| 2    | James | 35   | 6000   | 101        | Finance|
+------+-------+------+--------+------------+--------+

Here, the output includes all columns from both "employees" and "departments" where the "dept_id" column in "employees" matches the "id" column in "departments".

Explanation

In the example above, we used a natural join to combine two tables, "employees" and "departments". We used the "*" wildcard to select all columns from both tables in the result set.

The natural join specified that the join should be done on columns with matching names and data types, which in this case was "dept_id" in "employees" and "id" in "departments".

The output shows all columns from both tables that match the join condition.

Use

Natural join is useful when you want to join two or more tables based on their columns having matching names and data types. This can help simplify your queries and make them easier to read.

Important Points

• Natural join can only be used to join tables where the columns being joined have matching names and data types.
• When using natural join, it's important to ensure that the column names being joined are unique across all tables being joined.
• Natural join can be less efficient than other types of joins, such as inner join or left join, because it requires the database to compare all columns with the same name and data type in both tables being joined.

Summary

In this tutorial, we discussed the syntax, examples, uses, and important points of natural join in MySQL. Natural join is a useful way to join tables based on columns having matching names and data types, and can help simplify your queries and make them easier to read.