Sorting and Aliasing

Sorting and aliasing are two essential SQL techniques that help you control the presentation of query results and make your queries more readable and efficient.

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Sorting (ORDER BY)

The ORDER BY clause is used to sort the rows returned by a query in ascending or descending order.

Basic Syntax:

SELECT column1, column2
FROM table_name
ORDER BY column1 [ASC|DESC];

• ASC sorts in ascending order (default).
• DESC sorts in descending order.

Example:

SELECT first_name, last_name, hire_date
FROM employees
ORDER BY hire_date DESC;

Key Points:

• You can sort by one or multiple columns.
• Sorting affects the order of results but not the underlying table.
• Numeric positions can be used in ORDER BY (ORDER BY 2 DESC means order by the second column in the SELECT).

Example with Multiple Columns:

SELECT first_name, last_name, department
FROM employees
ORDER BY department ASC, last_name ASC;

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Aliasing (AS)

Aliases allow you to give a column or table a temporary name for the duration of a query. This makes results clearer and queries easier to read.

Column Aliases

Column aliases rename output columns.

Basic Syntax:

SELECT column_name AS alias_name
FROM table_name;

Example:

SELECT first_name AS "First Name", last_name AS "Last Name"
FROM employees;

• Quotes are required if the alias contains spaces or special characters.
• The AS keyword is optional in most databases: SELECT first_name "First Name" also works.

Table Aliases

Table aliases give a temporary name to a table — especially useful when using joins or subqueries.

Basic Syntax:

SELECT e.first_name, d.name
FROM employees AS e
JOIN departments AS d
  ON e.department_id = d.id;

• Here e and d are table aliases.
• Makes complex queries shorter and clearer.

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Why Use Aliases?

• Simplify long or complex table names.
• Make output column names clearer and user-friendly.
• Required for derived columns or calculated fields.

Example with Expression Alias:

SELECT salary * 12 AS annual_salary
FROM employees;

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Summary

Feature	Purpose	Example
ORDER BY	Sort rows	ORDER BY last_name DESC
Column Alias	Rename output columns	SELECT salary * 12 AS annual_salary
Table Alias	Shorten table names	FROM employees AS e

Sorting and aliasing help you write cleaner, more understandable queries and produce results in the exact format you need.