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 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 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;