Comments

A comment is a piece of text within a program that is not executed. It can be used to provide additional information to aid in understanding the code, or to prevent execution of SQL statements.

Single-line Comments

Single line comments start with --. Any text between -- and the end of the line will be ignored (will not be executed).

The following example uses a single-line comment as an explanation:

-- Select all:

SELECT *
FROM customers;

Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored.

The following example uses a multi-line comment as an explanation:

/* Select everything
from the customers table */

SELECT *
FROM customers;

The following example uses a multi-line comment to ignore many statements:

/* SELECT *
FROM customers;
SELECT *
FROM products; */

SELECT *
FROM orders;

To ignore just a part of a statement, also use the /* */ comment.

The following example uses a comment to ignore part of a line:

SELECT id, customer_name, /* city, */ country
FROM customers;