PostgreSQL comments.

Preamble

Can you place comments in your SQL statements in PostgreSQL? These comments can appear in one line or cover several lines. Let’s see how to do that.

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

The syntax is character usage; (two minuses)

The syntax for creating an SQL comment in PostgreSQL using the characters –:

-- here's a comment

In PostgreSQL, a comment starting with — is similar to a comment starting with #. When using — a comment must be at the end of a line in your SQL statement. This method of commenting can only take up one line in your SQL and should be at the end of a line.

Syntax for using the /* and */ characters

Syntax for creating an SQL comment in PostgreSQL using the characters /* and */:

/* here is the comment */

In PostgreSQL, there is a comment that starts with /* and ends with */ and can be found anywhere in your SQL statement. This method of commenting can take several lines.

A single-line comment

You can create an SQL comment on one line in your PostgreSQL SQL expression.

Consider an example of an SQL comment that shows an SQL comment that is on a single line and does not take several lines.

SELECT order_detail_id, quantity
/* Author: Jason */
FROM order_details;

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

SELECT /* Author: Jason */ order_detail_id, quantity
FROM order_details;

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

SELECT order_detail_id, quantity /* Author: Jason */
FROM order_details;

or

SELECT order_detail_id, quantity -- Author: Jason
FROM order_details;

Comment on a few lines

In PostgreSQL, you can create an SQL comment that takes several lines in your SQL statement. For example, you can create a comment:

SELECT order_detail_id, quantity
/*
* Author: Jason
* Purpose: to show a comment that takes several lines
* in your SQL statement in PostgreSQL.
*/
FROM order_details;

This SQL comment covers several lines in PostgreSQL – in this example, it takes 5 lines.

In PostgreSQL you can also create an SQL comment that takes several lines using this syntax:

SELECT order_detail_id, quantity /* Author: Jason
Purpose: To show a comment that takes several lines in your SQL statement. */
FROM order_details;

PostgreSQL will assume that everything after the /* character is a comment until it reaches the */ character, even if it takes several lines in an SQL statement. Thus, in this example, a comment will take up 2 lines within an SQL statement.

How to use comments in Postgres?

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