Mysql常用函数的汇总，可看下面系列文章
https://www.cnblogs.com/poloyy/category/1765164.html
按照指定的分隔符划分字符串，可指定分隔符出现的次数
SUBSTRING_INDEX(str, delim, count)
SELECT SUBSTRING_INDEX(‘www.mysql.com‘, ‘.‘, 1); # www SELECT SUBSTRING_INDEX(‘www.mysql.com‘, ‘.‘, -1); # com SELECT SUBSTRING_INDEX(‘www.mysql.com‘, ‘.‘, 2); # www.mysql SELECT SUBSTRING_INDEX(‘www.mysql.com‘, ‘.‘, -2); # mysql.com
假设有三个 IP：127.0.0.1、192.128.0.15、255.255.255.255，要分别取每一个号段的值并返回
SELECT ip, SUBSTRING_INDEX(ip,‘.‘,1) AS part1, SUBSTRING_INDEX(SUBSTRING_INDEX(ip,‘.‘,2),‘.‘,-1) AS part2, SUBSTRING_INDEX(SUBSTRING_INDEX(ip,‘.‘,-2),‘.‘,1) AS part3, SUBSTRING_INDEX(ip,‘.‘,-1) AS part4 FROM IPS;
+-----------------+-------+-------+-------+-------+ | ip | part1 | part2 | part3 | part4 | +-----------------+-------+-------+-------+-------+ | 127.0.0.1 | 127 | 0 | 0 | 1 | | 192.128.0.15 | 192 | 128 | 0 | 15 | | 255.255.255.255 | 255 | 255 | 255 | 255 | +-----------------+-------+-------+-------+-------+
中间的号段需要重复调用 SUBSTRING_INDEX，因为第一次调用的时候还是会返回两个号段
可以说是一个面试题，解法有多种，那么如果用 SUBSTRING_INDEX 要如何编写呢？
SELECT YEAR, SUBSTRING_INDEX( GROUP_CONCAT( amount ), ",", 1 ) AS m1, SUBSTRING_INDEX( SUBSTRING_INDEX( GROUP_CONCAT( amount ), ",", 2 ),",", -1 ) AS m2, SUBSTRING_INDEX( SUBSTRING_INDEX( GROUP_CONCAT( amount ), ",", - 2 ),",", 1 ) AS m3, SUBSTRING_INDEX( GROUP_CONCAT( amount ), ",", - 1 ) AS m4 FROM tests GROUP BY YEAR
Mysql 常用函数（42）- substring_index 函数
原文：https://www.cnblogs.com/poloyy/p/13268941.html