MySQL Extra:Using where 一定回表吗?
id时主键, name加了唯一索引。
explain select id, name from acto; 执行后Extra是Using index
explain select id, name from actor where id > 100;执行后Extra为什么是Using where?
explain select id, name from acto; 执行后Extra是Using index
explain select id, name from actor where id > 100;执行后Extra为什么是Using where?