This SQL tutorial focuses on the SQL Server Column Aliases, and provides explanations, examples and exercises. For this lesson’s exercises, use this link.
This tutorial is a part of several posts explaining how to write basic queries in SQL Server. To read additional posts regarding this subject, please use the following links:
- Writing Basic SQL SELECT statements
- SQL Arithmetic Operators
- SQL Column Aliases
- SQL String Concatenation
- SQL DISTINCT keyword
SQL Server Column Aliases
In SQL Server by default the column’s heading in the results produced by your query, is the original column’s name as it was defined in the table.
SELECT last_name FROM employees last_name ---------- David John
In many cases, column’s heading is not descriptive enough. In addition different operations, such as: string concatenation or mathematical calculation, will change the column’s heading to be even less readable and more difficult to understand:
SELECT 'Hello ' + last_name FROM employees (No column name) ---------------- Hello David Hello John
SQL Server Column Aliases are used to change column’s heading. Using the SQL Server Column Aliases the headings will be more easy to understand and more meaningful. To create a SQL Server Column Alias use the following syntax :
SELECT column_name AS 'Column_Alias' FROM table_name
For Example :
SELECT last_name, salary, salary + 500 AS 'NEW_SALARY' FROM employees
The result:
Last_name salary NEW_SALARY --------- ------- ------------------ Smith 5700 6200
You can also write the SQL Server column’s alias without the AS Keyword, for example:
SELECT last_name, salary, salary + 500 'NEW_SALARY' FROM employees
The result:
Last_name salary NEW_SALARY --------- ------ ------------------ Smith 5700 6200
It is also possible to write the SQL Server column’s alias without the enclosing single quotes (‘ ‘):
SELECT last_name, salary, salary + 500 new_salary FROM employees
The result:
Last_name salary new_salary ----------- ------ ------------------ Smith 5700 6200
- When a SQL Server column alias is written without enclosing single quotes (‘ ‘), it is not possible to write the alias as two (or more) separate words; you will have to insert some character between these words, underline (_) is most commonly used in these cases.
-- This query will generate an error -- The "New Salary" column alias should be enclosed within single quotes SELECT last_name, salary, salary * 1.1 AS New Salary FROM employees -- Insert an underline between these words : SELECT last_name, salary, salary * 1.1 AS New_Salary FROM employees -- Or use single quotes : SELECT last_name, salary, salary * 1.1 AS 'New Salary' FROM employees
- In order to make your SQL Server query more readable, always use the AS keyword, always use single quotes (‘ ‘), and when your alias consists of two words or more, always ensure that you insert an underline between them.
- Another common approach to handle an alias consists of two words or more, is to concatenate the words, and capitalize the first letter of each word :
SELECT last_name, salary, salary + 500 AS 'NewSalary' FROM employees