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SQL Server: Comments within SQL

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This SQL Server tutorial explains how to use comments within your SQL statements in SQL Server (Transact-SQL) with syntax and examples.

Description

Did you know that you can place comments within your SQL statements in SQL Server (Transact-SQL)? 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 SQL Server (Transact-SQL).

Syntax Using -- symbol

The syntax for creating a SQL comment using the -- symbol in SQL Server (Transact-SQL) is:

-- comment goes here

In SQL Server, a comment started with -- symbol 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 using /* and */ symbols in SQL Server (Transact-SQL) is:

/* comment goes here */

In SQL Server, 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 SQL Server (Transact-SQL).

Let's look at a SQL comment example that shows a SQL comment on its own line:

SELECT employee_id, last_name
/* Author: TechOnTheNet.com */
FROM employees;

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

SELECT  /* Author: TechOnTheNet.com */  employee_id, last_name
FROM employees;

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

SELECT employee_id, last_name  /* Author: TechOnTheNet.com */
FROM employees;

or

SELECT employee_id, last_name  -- Author: TechOnTheNet.com
FROM employees;

Example - Comment on Multiple Lines

In SQL Server (Transact-SQL), you can create a SQL comment that spans multiple lines in your SQL statement. For example:

SELECT employee_id, last_name
/*
 * Author: TechOnTheNet.com
 * Purpose: To show a comment that spans multiple lines in your SQL statement.
 */
FROM employees;

This SQL comment spans across multiple lines in SQL Server - in this example, it spans across 4 lines.

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

SELECT employee_id, last_name /* Author: TechOnTheNet.com
Purpose: To show a comment that spans multiple lines in your SQL statement. */
FROM employees;

SQL Server (Transact-SQL) 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.

posted Mar 1, 2017 by Shivaranjini

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