PRIMARY KEY是唯一性索引

添加表主键

ALTER TABLE `website` ADD PRIMARY KEY (`name`);

删除&修改表主键

ALTER TABLE `website` CHANGE `id` `id` INT UNSIGNED;
ALTER TABLE `website` DROP PRIMARY KEY;
ALTER TABLE `website` ADD PRIMARY KEY (`id`);
ALTER TABLE `website` CHANGE `id` `id` INT UNSIGNED AUTO_INCREMENT;

查看索引列表

SHOW INDEX FROM `website`;

添加普通索引

CREATE INDEX `name_index` ON `website` (`name`);

添加唯一性索引（设置唯一性后，无法添加重复内容）

CREATE UNIQUE INDEX `name_index` ON `website`(`name`(80));

删除索引

DROP INDEX `name_index` ON `website`;