KEY关键字是什么意思? [英] What does the KEY keyword mean?

问题描述

在此MySQL表定义中:

In this MySQL table definition:

CREATE TABLE groups (
  ug_main_grp_id smallint NOT NULL default '0',
  ug_uid smallint  default NULL,
  ug_grp_id smallint  default NULL,
  KEY (ug_main_grp_id)
);

KEY关键字是什么意思?它不是主键，也不是外键，所以它只是一个索引吗?如果是这样，用KEY创建的这种类型的索引有何特别之处?

What does the KEY keyword mean? It's not a primary key, it's not a foreign key, so is it just an index? If so, what is so special about this type of index created with KEY?

推荐答案

从 http://dev.mysql.com/doc/refman/5.1/en/create-table.html

{INDEX|KEY}

所以KEY是INDEX;)

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