Mysql: Comments Trick

Nice article by Eli White. Now you can understand easily all those comments that you see in the mysqldump output.


MySQL Trick with Comments

MySQL has a custom extension (if you want to call it that) to it’s commenting system, which actually allows you to make conditional commands. The mysqldump program that many people use to back up their databases uses this concept heavily, which is where I first ran into it.

In it’s simplest form, this allows you to place commands in a SQL file that only MySQL will run:

/*! MySQL specific code */

This allows you to make a single SQL file, that not only will execute correctly (and in detail) on MySQL, but it will also work on any ANSI compatible database, since you’ve hidden any of the non-ANSI parts in MySQL conditional comments. So for example, MySQL allows you to set a variable declaring that all names will be a certain character set, such as UTF-8, and therefore you can do:

/*! SET NAMES utf8 */;