SQL Alias

If you have very long or complex tables name or columns name than it can be denoted with their alias.
There are two types of aliases that are used most frequently:

·         Column alias and

·         Table alias.

Syntax for Tables Alias:

SELECT column_name(s) FROM table_name AS alias_name

Example:

SELECT s.first_name,s.Last_Name FROM student_details s;

Note: In the above query, alias 's' is defined for the table student_details and the column first_name and Last_Name is selected from the table.

Syntax for Columns Alias:

SELECT column_name AS alias_name FROM table_name

Example:

SELECT first_name AS Name FROM student_details; or SELECT first_name Name FROM student_details;

Result will look like this:

Name

Priya Chandra

Anjali Bhagwat

Rahul Sharma

An Example of both Column alias and Table alias


Suppose we have a table called "tbl_Employee" and another table called "tbl_Department". We will give the table aliases of "e" and "d" respectively.
Now we want to list all the Employees with there Departments.


We use the following SELECT statement:

SELECT e.EmpID, e.EmpName, d.DeparmentName FROM tbl_Employee AS e, tbl_Department AS d WHERE e.EmpID=d.EmpID_fk

The same SELECT statement without aliases:

SELECT tbl_Employee.EmpID, tbl_Employee.EmpName, tbl_Department.DeptName FROM tbl_Employee, tbl_Department WHERE tbl_Employee.EmpID=tbl_Department.EmpID_fk

As you'll see from the two SELECT statements above; aliases can make queries easier to both write and to read.

Advantages of Alias:

1.     There are more than one tables involved in a query,

2.     Functions are used in the query,

3.     The column names are big or not readable,

4.     More than one columns are combined together.