Difference Between Equi Join And Natural Join

Databases are an essential part of any modern computer system. They allow us to store and retrieve data easily and efficiently, and are used in a wide range of applications, from finance and healthcare to social media and e-commerce. As the use of databases has grown, so too has the need for sophisticated techniques for managing and querying them. Two such techniques are Equi Join and Natural Join. In this article, we will explore the difference between these two techniques and the circumstances in which each is most appropriate.

Equi Join and Natural Join

Equi Join and Natural Join are two types of Join operations used in Relational Database Management System (RDBMS). Joins are used to combine rows from two or more tables based on a related column between them. In other words, join is used to retrieve data from multiple tables by connecting them based on a relationship that exists. Let's take an example:

Table: Employee

| Emp_ID | Emp_Name | Emp_Salary | Dept_ID |

|--------|----------|------------|---------|

| 1 | Joe | 50000 | 1 |

| 2 | Sarah | 60000 | 2 |

| 3 | Tom | 55000 | 1 |

| 4 | Rachel | 65000 | 2 |

Table: Department

| Dept_ID | Dept_Name |

|---------|-----------|

| 1 | HR |

| 2 | IT |

| 3 | Finance |

The above two tables have a relationship based on department id. Each employee belongs to one department. Now, if we want to retrieve data of employees along with their respective department names, we use the join operation. There are two types of join operations that can be used - Equi Join and Natural Join.

Equi Join

Equi Join is a join operation that is based on the comparison of equality between the values in the related columns. Equi Join is denoted by the operator = or the keyword JOIN. In Equi Join, the join condition compares the values of the columns of the two tables and returns only the rows where the values match.

Let's take an example of an Equi Join query:

SELECT Employee.Emp_ID, Employee.Emp_Name, Department.Dept_Name

FROM Employee

JOIN Department ON Employee.Dept_ID = Department.Dept_ID;

In the above query, we have retrieved the columns Emp_ID, Emp_Name, and Dept_Name from the tables Employee and Department. We have connected the two tables using the join condition Employee.Dept_ID = Department.Dept_ID. This condition returns only the rows where the values in the column Dept_ID of both the tables match.

Natural Join

Natural Join is a join operation that is based on the columns having the same name and data type in the related tables. Natural Join is denoted by the keyword NATURAL JOIN. In Natural Join, the join condition compares all the columns having the same name and data type in both the tables and returns only the matching rows.

Let's take an example of a Natural Join query:

SELECT Employee.Emp_ID, Employee.Emp_Name, Department.Dept_Name

FROM Employee

NATURAL JOIN Department;

In the above query, we have retrieved the columns Emp_ID, Emp_Name, and Dept_Name from the tables Employee and Department. We have connected the two tables using the Natural Join operation. Since both the tables have a column named Dept_ID, the Natural Join operation will compare this column and return only the rows where the values in this column of both the tables match.

Difference Between Equi Join And Natural Join

The primary difference between Equi Join and Natural Join is the way they compare the columns in the related tables. Equi Join compares the columns based on equality, whereas Natural Join compares the columns based on the same name and data type. Equi Join can be used when we need to compare columns other than the related columns, while Natural Join can be used only when the related columns have the same name and data type.

Another difference between Equi Join and Natural Join is the way they handle duplicate column names. In Equi Join, if the two tables have two columns with the same name, we need to qualify each column with the respective table name to avoid ambiguity. In Natural Join, the duplicate columns are automatically removed from the result set.

Equi Join and Natural Join also have different performance characteristics. Equi Join uses an Index or Hash Join algorithm, which is more efficient when the tables are large and the columns being compared are indexed. Natural Join uses a Cartesian Product algorithm, which performs poorly on large tables and should be avoided.

Conclusion

In conclusion, Equi Join and Natural Join are two important join operations used in Relational Database Management System (RDBMS). Equi Join compares the related columns based on equality, whereas Natural Join compares the related columns based on the same name and data type. Equi Join can be used when we need to compare columns other than the related columns, while Natural Join can be used only when the related columns have the same name and data type. Equi Join uses an Index or Hash Join algorithm, which is more efficient when the tables are large and the columns being compared are indexed. Natural Join uses a Cartesian Product algorithm, which performs poorly on large tables and should be avoided. By understanding the difference between Equi Join and Natural Join, we can choose the appropriate join operation for our database queries and achieve optimal performance.