如何用SQL query证明更短索引更有效率？

Question

A database administrator wants to create an index on the address column in the CUSTOMER_MSTR table. Their statement is below:
CREATE INDEX ADDRESS ON CUSTOMER_MSTR (Address(64));
You think the index can be a lot shorter and therefore more efficient. Write an example SQL query that you could run to show that an index based on Address with a length of 32 characters is just as good as one with a length of 64 characters.
题目说在CUSTOMER_MSTR表中在address建一个index如下：
CREATE INDEX ADDRESS ON CUSTOMER_MSTR (Address(64));
你认为index没必要那么长因此能够更加有效。写一个可以运行的SQL查询来表明32个字母长度的地址和64个长度的地址运行一样好？

Answer 1

按你描述的应该是说前缀索引，通过截取字段的前n个字段作为索引，在缩小索引大小的同时，尽量覆盖更多的数据，速度下降不多。
可以查看https://zhuanlan.zhihu.com/p/...，里面对前缀索引的描述。