• Learning MySQL By Example
  • Introduction
  • 1. How to Retrieve Data From a Single Table
  • 2. How to Retrieve Data from Multiple Tables
  • 3. Using Functions
  • 4. How to Insert, Update, Delete Data in Tables
  • 5. Summary Queries and Aggregate Functions
  • 6. Working With Subqueries
  • 7. SQL Views
  • 8. SQL Indexes
  • Glossary
  • Index
  • Download
  • Translations
  • 1.5

    Column Aliases

    Column Aliases

    • A column alias provides a way to create a clean or more descriptive header for a results set.
    • A column alias cannot be used in a SELECT, WHERE, GROUP BY or HAVING clause due to the order of execution. You must refer to the original column name.

    In the previous example, we created a new column that was a calculated value. The problem is that the column header is now population / SurfaceArea. However, we can rename the column header to something cleaner by creating a column alias.  Look at the code snippet below.


    SELECT name, population / SurfaceArea
         AS “People per square mile”
    FROM country;

    We used the AS keyword then in quotes we put the new column alias of “People per square mile.” Which changes the column header as seen show below.



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