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PostgreSQL : Comments within SQL

Tutorial by:      Date: 2016-04-19 23:32:06

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This PostgreSQL tutorial explains how to use comments within your SQL statements in PostgreSQL with syntax and examples.

Description

Did you know that you can place comments within your SQL statements in PostgreSQL? These comments can appear on a single line or span across multiple lines. Let's look at how to do this.

Syntax

There are two syntaxes that you can use to create a comment within your SQL statement in PostgreSQL.

Syntax Using -- symbol

The syntax for creating a SQL comment in PostgreSQL using -- symbol is:

-- comment goes here

In PostgreSQL, a comment started with -- symbol is similar to a comment starting with # symbol. When using the -- symbol, the comment must be at the end of a line in your SQL statement with a line break after it. This method of commenting can only span a single line within your SQL and must be at the end of the line.

Syntax Using /* and */ symbols

The syntax for creating a SQL comment in PostgreSQL using /* and */ symbols is:

/* comment goes here */

In PostgreSQL, a comment that starts with /* symbol and ends with */ and can be anywhere in your SQL statement. This method of commenting can span several lines within your SQL.

Example - Comment on a Single Line

You can create a SQL comment on a single line in your SQL statement in PostgreSQL.

Let's look at a SQL comment example that shows a SQL comment that is on a single line and does not span multiple lines.

SELECT order_detail_id, quantity/* Author: Fastread.aitechtonic.com */FROM order_details;

Here is a SQL comment that appears in the middle of the line:

SELECT  /* Author: Fastread.aitechtonic.com */  order_detail_id, quantityFROM order_details;

Here is a SQL comment that appears at the end of the line:

SELECT order_detail_id, quantity  /* Author: Fastread.aitechtonic.com */FROM order_details;

or

SELECT order_detail_id, quantity  -- Author: Fastread.aitechtonic.comFROM order_details;

Example - Comment on Multiple Lines

In PostgreSQL, you can create a SQL comment that spans multiple lines in your SQL statement. For example:

SELECT order_detail_id, quantity/* * Author: Fastread.aitechtonic.com * Purpose: To show a comment that spans multiple lines in your SQL * statement in PostgreSQL. */FROM order_details;

This SQL comment spans across multiple lines in PostgreSQL - in this example, it spans across 5 lines.

In PostgreSQL, you can also create a SQL comment that spans multiple lines using this syntax:

SELECT order_detail_id, quantity /* Author: Fastread.aitechtonic.comPurpose: To show a comment that spans multiple lines in your SQL statement. */FROM order_details;

PostgreSQL will assume that everything after the /* symbol is a comment until it reaches the */ symbol, even if it spans multiple lines within the SQL statement. So in this example, the SQL comment will span across 2 lines within the SQL statement.

 

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