Oracle / PLSQL: Comments within SQL

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

Description

Did you know that you can place comments within your SQL statements in Oracle? 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 Oracle/PLSQL.

Syntax Using -- symbol

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

-- <strong>comment goes here</strong>

In Oracle, 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 in Oracle using /* and */ symbols is:

/* <strong>comment goes here</strong> */

In Oracle, 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 Oracle/PLSQL.

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

SELECT suppliers.supplier_id
/* Author: aodba.com */
FROM suppliers;

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

SELECT  /* Author: aodba.com */  suppliers.supplier_id
FROM suppliers;

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

SELECT suppliers.supplier_id  /* Author: aodba.com */
FROM suppliers;

or

SELECT suppliers.supplier_id  -- Author: aodba.com

FROM suppliers;

Example - Comment on Multiple Lines

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

SELECT suppliers.supplier_id
/*
 * Author: aodba.com
 * Purpose: To show a comment that spans multiple lines in your SQL statement.
 */
FROM suppliers;

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

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

SELECT suppliers.supplier_id /* Author: aodba.com
Purpose: To show a comment that spans multiple lines in your SQL statement. */
FROM suppliers;

Oracle/PLSQL 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.