Right Join - (MariaDB Joins)
A right join is a type of join in MariaDB that returns all the rows from the right table and matching rows from the left table. If there are no matching rows in the left table, the result will contain null values.
Syntax
The syntax for performing a right join in MariaDB is as follows:
SELECT columns
FROM table1
RIGHT JOIN table2
ON condition;
Here, table1 is the left table and table2 is the right table. The ON clause specifies the condition for joining the tables, and columns list the columns to be returned in the result set.
Example
Consider two tables, employees and departments, with the following data:
employees
| id | first_name | last_name | department_id |
|---|---|---|---|
| 1 | John | Doe | 1 |
| 2 | Alice | Smith | 2 |
| 3 | Bob | Johnson | NULL |
departments
| id | name |
|---|---|
| 1 | Sales |
| 2 | Marketing |
| 3 | Engineering |
Here is an example of using a right join to join the departments table with the employees table:
SELECT *
FROM departments
RIGHT JOIN employees
ON departments.id = employees.department_id;
Output
The output of the above query will be:
| id | name | id | first_name | last_name | department_id |
|---|---|---|---|---|---|
| 1 | Sales | 1 | John | Doe | 1 |
| 2 | Marketing | 2 | Alice | Smith | 2 |
| NULL | NULL | 3 | Bob | Johnson | NULL |
Explanation
In the above example, we are joining the departments table with the employees table using a right join. We are selecting all columns from both tables. The ON clause specifies that we should join the tables based on the id column in the departments table and the department_id column in the employees table.
The first two rows in the output match records from the employees table where there is a matching record in the departments table. The final row shows that there are no matching records in the departments table for the employee with a NULL department ID.
Use
The right join can be used in situations where you want to include all records from the right table regardless of whether there is a matching record in the left table. This can be useful in scenarios where you need to include data even if it is incomplete.
Important Points
- A right join returns all the rows from the right table and matching rows from the left table.
- If there are no matching rows in the left table, the result will contain null values.
- The right join can be useful in scenarios where you need to include data even if it is incomplete.
Summary
In summary, a right join is a type of join in MariaDB that returns all the rows from the right table and matching rows from the left table. It can be used in situations where you need to include data even if it is incomplete.