SQL Comments – Tutorial with Examples

SQL Comments are an important part of the SQL programming language, used to add annotations or explanations to the code for better readability and understanding. Comments are not executed or executed by the database and serve only to improve the readability of the code for the developer or someone else who might be reading it in the future.

Types of SQL Comments

There are two types of comments in SQL:

  1. Single-line Comments: A single-line comment begins with two hyphens (–) and continues to the end of the line. For example:
-- This is a single-line comment in SQL
  1. Multi-line Comments: A multi-line comment is used to comment out multiple lines of code and starts with /* and ends with */. For example:
This is a multi-line
comment in SQL

Benefits of Using SQL Comments

  • Documentation: Comments are a valuable tool for documenting the code and explaining the purpose and logic behind it. This can help other developers or anyone else who reads the code to better understand it and make changes as needed.
  • Debugging: Comments can also be used to temporarily comment out sections of code for debugging purposes. This allows developers to easily isolate and test specific parts of the code without having to delete or modify it permanently.
  • Maintenance: Properly commented code can also make it easier to maintain and update over time, as the purpose and logic of the code is clearly explained and documented.

It is important to note that the syntax for comments may vary slightly between different database management systems. For example, in some systems, single-line comments may start with a hash symbol (#) instead of two hyphens.

Example of Using SQL Comments

Here is an example of how SQL comments can be used in a SQL statement to provide additional context and information:

-- This selects all columns from the table named customers
FROM customers; 

This is a select statement
It fetches only those customers
having ID greater than 500
SELECT * FROM customers WHERE ID>500;


SQL comments are a valuable tool for documenting, debugging, and maintaining SQL code. They help to improve the readability and understanding of the code for developers and other people who may read it in the future. It is important to use comments effectively and consistently in SQL code to ensure that the purpose and logic behind the code are clearly explained. Whether you are writing single-line or multi-line comments, the key is to use them to provide additional context and information that will help others understand and work with your code more easily. Overall, incorporating SQL comments into your coding practice can lead to more organized, maintainable, and efficient code.

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