用explain分析sql后结果的疑惑

Question

explain select * from user where id =1 or id = 2

explain select id from user where id =1 or id = 2

不是说用or会导致索引失效吗？为什么type不是all

而且select * 的时候 type是range

select id 的时候，type是index，比 select * 级别还低？但是extra却显示using index？

Answer 1

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