创建唯一索引和普通索引

/*创建表时创建索引：
create table [表名](
	[属性名1] [数据类型1] [约束1],
	...
	[属性名n] [数据类型n] [约束n],

	[unique | fulltext | spatial] index|key [索引名](
		[属性名1] [(长度)] [asc | desc],
		...
		[属性名n] [(长度)] [asc | desc]
	)
);
在已创建的表格上创建索引：
alter table [表名] add [unique|fulltext|spatial] [index|key] [索引名](
		[属性名1] [(长度)] [asc | desc],
		...
		[属性名n] [(长度)] [asc | desc]
	);
*/
create unique index uniq_idx_firstname on actor(first_name);
create index idx_lastname on actor(last_name);

自测一直报错，直接提交就通过了，为啥呢？？