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SQL Alias

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As in normal life we associate some nicknames with people, or call them with names that are not there actual names SQL also allows us to do the same with the table columns, since it is much easier to memorize, view as it is in real life. Now the point where SQL ALIAS becomes important is that whenever we have a table which has complex column names we can easily rename the column understand it easily.

NOTE that SQL Alias will not change the actual name of the column in the table.

The SQL ALIAS can be used on any column of any table, but cannot use the reserved word.

SQL ALIAS Syntax for Columns

SELECT column_name(s) As ALIAS_NAME FROM table_name

Consider the following table for this exercise

Users

Firstname Lastname Salary DeptNumber
John Smith 1000 1
Mathew Simon 3000 1
Bill Steve 2200 1
Amanda Rogers 1800 2
Steve Hills 2800 2
Steve jobs 2400 2
bill cosby 700 3

Departments

Dept_No DepartmentName
1 Employee
2 Management
3 Staff


Example # 1

SELECT Firstname AS First_Name, Lastname AS Last_Name, salary AS Monthly_Salary, DeptNumber AS Department_Code FROM users

Result of the Query

First_Name Last_Name Monthly_Salary Department_Code
John Smith 1000 1
Mathew Simon 3000 1
Bill Steve 2200 1
Amanda Rogers 1800 2
Steve Hills 2800 2
Steve jobs 2400 2
bill cosby 700 3

Notice that the column names has been changed as mentioned in the query.

The SQL Alias can also be use for table name, which can simplify the JOIN operations, The Alias name for table also work the same way as it works for the columns.

SQL ALIAS Syntax for Tables

SELECT column_name(s) FROM table_name AS alias_name

Consider the following example.

Example # 2

SELECT Firstname AS First_Name, Lastname AS Last_Name, salary AS Monthly_Salary, DepartmentName FROM users AS U JOIN Departments AS D WHERE U.deptnumber=D.Dept_No

Result of the Query

First_Name Last_Name Monthly_Salary DepartmentName
John Smith 1000 Employee
Mathew Simon 3000 Employee
Bill Steve 2200 Employee
Amanda Rogers 1800 Management
Steve Hills 2800 Management
Steve jobs 2400 Management
bill cosby 700 Staff

We have joined the two tables, and in the WHERE clause the alias name is used as a reference to the table, if you do not know how to join a table then please see the SQL JOIN tutorial.

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