SQL - Comments

---

---

SQL Comments

SQL comments are notes you can add inside your SQL code to explain what the code does. The database ignores these comments when running queries, but they help developers read, understand, and maintain the code. Comments are also useful for temporarily disabling parts of a query without deleting them.

Types of SQL Comments

SQL supports three main types of comments:

• Single-line comments: These comments are used for one line of text. Start the comment with --. Everything after -- on that line is ignored by the database.
• Multi-line comments: These comments are used for longer explanations across multiple lines. They are enclosed between /* and */.
• Inline comments: These comments are placed at the end of a SQL statement or line of code to add a brief explanation.

SQL Single Line Comments

The SQL single line comments are used to write short notes for a single line of SQL code. Everything written after -- on the same line is ignored by the database engine. These comments are ideal for briefly explaining a query or temporarily disabling a single line.

Syntax

Following is the syntax of SQL single line comment:

-- This is a single line comment

Example

In the following query, we are using a single line comment to write a text:

-- Will fetch all the table records
SELECT * from table;

SQL Multi-Line Comments

The SQL multi line comments are used to comment out multiple lines or a block of SQL code. It starts with /* and ends with */. Entire text between these delimiters (/*...*/) will be ignored and considered as a comment.

Syntax

Following is the syntax of SQL multi line comments:

/* This is a
   multi-line
   comment */

Example

The following example uses multi-line comment as an explanation of the query:

/*following query 
will fetch all the 
table records./*
SELECT * from CUSTOMERS;

SQL Inline Comments

The SQL inline comments are written at the end of a SQL statement or code line. They are used to quickly explain what a specific part of the query does, without affecting how the query runs. Inline comments are useful when you want to give a short clarification right next to the code.

Syntax

Following is the syntax of SQL inline comment:

SELECT column_name -- This is an inline comment
FROM table_name;

Example

The following example shows how to use an inline comment to explain each part of a query:

SELECT id, name, salary -- Fetch employee id, name, and salary
FROM employees
WHERE salary > 50000; -- Only include employees with salary greater than 50,000