ORDER BY - (PostgreSQL Clause)

The ORDER BY clause is used to sort the result set in ascending or descending order. In PostgreSQL, the ORDER BY clause is used in conjunction with the SELECT statement.

In this tutorial, we'll discuss the syntax, example, output, explanation, use, important points, and summary of the ORDER BY clause in PostgreSQL.

Syntax

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

• column1, column2, ...: The columns to sort the result set by.
• table_name: The table to retrieve data from.
• ASC (optional): Sort the result set in ascending order. (default)
• DESC (optional): Sort the result set in descending order.

Example

Let's take a look at a simple example of using ORDER BY clause in PostgreSQL.

SELECT * 
FROM employees 
ORDER BY last_name ASC;

In the above example, we're retrieving all columns from the employees table and sorting them in ascending order by the last_name column.

Explanation

In SQL, the ORDER BY clause is used to sort a result set. By default, the ORDER BY clause sorts data in ascending order. However, you can also specify the DESC keyword to sort data in descending order.

The ORDER BY clause can be used with any column in a table, including computed columns. You can also use multiple columns to sort the result set. In this case, the result set will be sorted by the first column, and if two rows have the same value in the first column, they will be sorted by the second column, and so on.

Use

The ORDER BY clause is used to sort the result set by one or more columns. This is useful when you need to present data in a certain order, such as sorting a list of products by name or sorting a list of employees by last name.

Important Points

• The order of the ORDER BY clause in the SQL statement is important. If you want to sort by multiple columns, make sure you specify them in the order you want them to be sorted.
• If you're sorting by a computed column, make sure you use the same expression in the ORDER BY clause as you did in the SELECT clause.
• If you want to sort by a column that contains NULL values, you can use the NULLS FIRST or NULLS LAST clauses to specify where the NULL values should appear in the result set.

Summary

In this tutorial, we discussed the ORDER BY clause in PostgreSQL. We covered the syntax, example, output, explanation, use, important points, and summary of the ORDER BY clause. With this knowledge, you can now use the ORDER BY clause to sort the result set in ascending or descending order in your PostgreSQL queries.