What is the difference Rename and Alias In DBMS

In this article, we are going to study Rename and Alias. Both these have their specific role when we talk in terms of DBMS. Renaming and aliases to the elements of the database provide a layer of abstraction and make the attributes of the relation presentable for the viewer. Mostly, Database store crucial information the concepts of renaming and aliasing plays an important role in representing data with efficiency. Let's gain an understanding of these concepts, their syntax, and the difference between them.

What is Alias?

Alias is an alternative name given to a column in the database Management System. This practice offers the advantage of assigning distinct and easily recognizable names to columns, enhancing their specificity.

Let’s Look Into its Syntax

Select columnName As AliasName from TableName;

For instance

Consider a table "Employee" containing attributes such as name, eid, salary, designation, and D.O.J. In a scenario where only the salary column is to be displayed with the name of "Annual-Salary," the concept of alias comes into play. This is achieved by employing the "AS" keyword, which serves as a reference to the assigned alias.

Original Table

empid	emp_name	salary
101	Sam	20000
102	Carl	30000
103	Tom	40000
104	Nick	70000

Select empid, Salary AS Annual_Salary from Employee;

Output

empid	Annual_Salary
101	20000
102	30000
103	40000
104	70000

You can apply the Alias name concept on multiple columns in one query.

Alias Name for Table

It helps to differentiate the column from the different tables that may or may not have the same name.

Let’s understand the concept of Alias name for a table by the below example

Manager Table

Managerid	empid	ManagerName
1001	101	Sam
1002	104	Nick

Employee table

empid	emp_name	salary
101	Sam	20000
102	Carl	30000
103	Tom	40000
104	Nick	70000

Select E.empid , M.empid , Salary from Employee As E , Manager As M

Where E.empid = M.empid ;

Output

empid	Salary
101	20000
104	70000

In the example provided earlier, "E" and "M" serve as aliases for the "Employee" and "Manager" tables, respectively. The utilization of aliases becomes particularly relevant when distinguishing between the "empid" values in these tables. This is where the concept of aliasing comes into effect. The "WHERE" clause, in this context, facilitates the identification of shared rows that possess identical "empid" values across both tables.

What is Rename?

So far you explored the Alias now, you will get an idea about the Rename concept in Database and how to use it. It is used to change the name of an object table, or column. This practice holds the purpose of attributing meaningful and relevant names to these elements. These designated names, though temporary and not permanent alter the structure of the tables.

Let's Look Into its Syntax

RENAME TableName TO NewName

Consider, for instance, an "Employee" table; through renaming, we can metamorphose it into a more contextual and expressive title.

Rename Employee TO Emp;

This syntax can be different for different databases and different databases can have their own norms and set of rules which we have to follow while renaming the table and column names.

By altering column names – such as changing salary to YearlySal. You can heighten the readability and comprehensibility of data, all the while preserving the original structure of the table.

Syntax

ALTER TABLE TableName RENAME COLUMN OldColumn TO New Column;

For Instance

ALTER TABLE EMP RENAME Salary TO YearlySal;

Output

empid	Annual_Salary
101	20000
102	30000
103	40000
104	70000

Difference Between the Rename and Alias

"Alias" and "Rename" are concepts frequently utilized in the context of databases, each serving distinct roles. Let’s see the difference between them by using the table mentioned below −

Characteristics	Alias	Rename
Purpose	An alias provides a provisional or substitute name for a table or column within a specific query. Its purpose is to enhance query legibility, simplify complex queries, and assign more descriptive labels to columns or expressions in the query result. These aliases are confined to the scope of an individual query and have no impact on the official names of database objects in the schema.	Renaming involves altering the name of a database object—such as a table, column, index, or constraint—within the actual database schema. This name change is persistent across the entirety of the database. Renaming proves valuable when striving to align names with the true purpose of an object or to rectify naming errors.
Scope	This changes the names temporarily and does not affect the structure of the table.	This changes the name permanently like the table name Employee to emp in the above case.
Keyword use	In the case of Alias, the column name is achieved by using ‘AS’ or without AS	In this, we can change the column name by using the Alter table statement along with RENAME
Example	SELECT e.empid, d.empid, e.first_name AS "FirstName", d.department_name FROM employees AS e, Department AS d Where e.empid=d.empid In this example, "e" and "d" are employed as table aliases, and "FirstName" serves as a column alias.	ALTER TABLE old_table_name RENAME TO new_table_name; The above modifies the table name to "new_table_name".

Conclusion

An alias offers a momentary label used in a single query to enhance query clarity and temporarily assign names to columns or tables. In contrast, renaming represents a lasting modification that changes the actual name of a database object across the entire database schema.