KEY`ix_deleted`（`deleted`）创建表

Question

CREATE TABLE `blog` (
    `id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
    `title` text,
    `content` text,
    `deleted` tinyint(1) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id`),
    KEY `ix_deleted` (`deleted`)
) ENGINE=InnoDB
  AUTO_INCREMENT=1
  DEFAULT CHARSET=utf8
  COMMENT='Blog posts';

我已创建表格，我想实现触发器。我想知道这个查询中这行代码的目的是什么。

KEY `ix_deleted` (`deleted`)