我有一个像这样的表结构
comment_id primary key
comment_content
comment_author
comment_author_url
当我触发查询时
explain SELECT * FROM comments ORDER BY comment_id
它将结果输出为
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE comments ALL NULL NULL NULL NULL 22563 Using filesort
为什么找不到我定义为主键的索引?