SQL comments can be divided into two types:

1.  Single-Line Comments:

The most basic form of SQL comment is the single-line comment. In SQL, a line beginning with two consecutive hyphens (–), known as a double-dash, is treated as a comment. For example:

-- This is a single-line comment
SELECT * FROM employees;

Single-line comments are handy for adding brief explanations to specific lines of code, making it easier for developers to understand the purpose or context of a particular query.

2. Multi-Line Comments:

In addition to single-line comments, SQL also supports multi-line comments. These are enclosed within /* and */, allowing developers to add more extensive comments spanning multiple lines. Multi-line comments are particularly useful for documenting complex queries or providing detailed explanations. Here’s an example:

/*
This is a multi-line comment
that provides additional information
about the purpose of the SQL query.
*/
SELECT column1, column2
FROM orders
WHERE order_date > '2023-01-01';

Using multi-line comments, developers can offer comprehensive insights into the logic and rationale behind a series of SQL statements.