SQL RIGHT JOIN

The RIGHT JOIN keyword in SQL returns all records from the right table, and the matched records from the left table. The result is NULL from the left side, when there is no match.

Here's the basic syntax:

SELECT column_name(s)
FROM table1
RIGHT JOIN table2
ON table1.column_name = table2.column_name;

Consider the following two tables:

Table "Orders"

OrderID	CustomerID	OrderDate
1	3	2023-01-01
2	1	2023-02-01
3	2	2023-03-01

Table "Customers"

CustomerID	CustomerName	ContactName	Country
1	Alfreds	Maria	Germany
2	Ana Trujillo	Ana	Mexico
3	Antonio	Antonio	Mexico
4	Around the Horn	Thomas	UK

Let's apply a RIGHT JOIN with these two tables:

SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
RIGHT JOIN Customers
ON Orders.CustomerID = Customers.CustomerID;

This SQL statement would return:

OrderID	CustomerName
1	Antonio
2	Alfreds
3	Ana Trujillo
NULL	Around the Horn

This is because the RIGHT JOIN keyword returns all records from the right table (Customers), and the matched records from the left table (Orders). The result is NULL from the left side, when there is no match.

Note: Not all database systems support RIGHT JOIN. However, you can always achieve the same result with a LEFT JOIN, just swapping the position of the tables. The SQL syntax may vary slightly between different SQL dialects, so always consult the relevant documentation if unsure.

When to Use RIGHT JOIN in SQL:
- Description: Use RIGHT JOIN when you want to retrieve all records from the right table and matching records from the left table. It ensures that unmatched records from the right table are also included.
- Code Example:
```
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.column_name = table2.column_name;
```
SQL RIGHT JOIN vs LEFT JOIN:
- Description: The primary difference is the direction of inclusion. RIGHT JOIN includes all records from the right table and matching records from the left table, while LEFT JOIN includes all records from the left table and matching records from the right table.
- Code Example:
```
-- RIGHT JOIN
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.column_name = table2.column_name;

-- LEFT JOIN
SELECT *
FROM table1
LEFT JOIN table2 ON table1.column_name = table2.column_name;
```

Multiple Tables RIGHT JOIN in SQL:

Description: You can perform RIGHT JOIN on multiple tables by extending the JOIN clause.

Code Example:

SELECT *
FROM table1
RIGHT JOIN table2 ON table1.column_name = table2.column_name
RIGHT JOIN table3 ON table2.column_name = table3.column_name;

Common Mistakes with SQL RIGHT JOIN:

Common Mistake: Confusing the order of tables in the JOIN clause.

-- Mistake: Incorrect order of tables in RIGHT JOIN
SELECT *
FROM table2
RIGHT JOIN table1 ON table1.column_name = table2.column_name;

Using WHERE Clause with RIGHT JOIN in SQL:
- Description: You can use the WHERE clause to further filter the result of a RIGHT JOIN.
- Code Example:
```
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.column_name = table2.column_name
WHERE table1.column_name IS NULL;
```

Nested RIGHT JOIN in SQL:

Description: You can nest RIGHT JOINs to join multiple tables in a hierarchical manner.

Code Example:

SELECT *
FROM table1
RIGHT JOIN (
    table2
    RIGHT JOIN table3 ON table2.column_name = table3.column_name
) ON table1.column_name = table2.column_name;

Impact of NULL Values in RIGHT JOIN:
- Description: If there is no match on the left table, the columns from the left table will contain NULL values. Handle NULLs appropriately in SELECT or WHERE clauses.
- Code Example:
```
SELECT table1.column1, COALESCE(table2.column2, 'N/A') AS column2
FROM table1
RIGHT JOIN table2 ON table1.column_name = table2.column_name;
```