-- style of comment, which requires a trailing space, differs in behavior from the SQL standard, which does not require the space.
There are three types of comment:
# This comment continues to the end of line -- This comment continues to the end of line /* This is an in-line comment */ /* This is a multiple-line comment */
SELECT * FROM t1; -- this is comment CREATE TABLE stack( /* id_user int, username varchar(30), password varchar(30) */ id int );
-- method requires that a space follows the
-- before the comment begins, otherwise it will be interpreted as a command and usually cause an error.
# This comment works /* This comment works. */ -- This comment does not.
Commenting table definitions
CREATE TABLE menagerie.bird ( bird_id INT NOT NULL AUTO_INCREMENT, species VARCHAR(300) DEFAULT NULL COMMENT 'You can include genus, but never subspecies.', INDEX idx_species (species) COMMENT 'We must search on species often.', PRIMARY KEY (bird_id) ) ENGINE=InnoDB COMMENT 'This table was inaugurated on February 10th.';
COMMENT is optional. (Official docs)
These comments, unlike the others, are saved with the schema and can be retrieved via
SHOW CREATE TABLE or from