你遇到这个问题是因为你没有安装MySql。在安装mysql2 gem之前。安装MySQL。之后将安装mysql2 gem。

对我来说，这很有帮助:

$ export LDFLAGS="-L/usr/local/opt/openssl/lib"
$ export CPPFLAGS="-I/usr/local/opt/openssl/include"

然后:

gem install mysql2 -v '0.5.2' --source 'https://rubygems.org/' -- --with-cppflags=-I/usr/local/opt/openssl/include --with-ldflags=-L/usr/local/opt/openssl/lib

结果:

Building native extensions with: '--with-cppflags=-I/usr/local/opt/openssl/include --with-ldflags=-L/usr/local/opt/openssl/lib'
This could take a while...
Successfully installed mysql2-0.5.2
Parsing documentation for mysql2-0.5.2
Installing ri documentation for mysql2-0.5.2
Done installing documentation for mysql2 after 0 seconds
1 gem installed

请看这篇文章(警告:里面有日语)。

在Debian Stretch上，适合我的包是default-libmysqlclient-dev

Sudo apt-get update && apt-get install -y default-libmysqlclient-dev

下载正确版本的mysqllib.dll，然后复制到ruby bin，这对我来说真的很有用。请按照这个链接mysql2 gem编译错误的mysql客户端库

你试过用

 gem install mysql -- --with-mysql-lib=/usr/lib/mysql/lib 

来指定基本目录的位置以及完成gem安装所必需的MySQL库的路径?

来源: MySQL Gem安装错误:未能建立Gem本地扩展 MySQL论坛::Ruby::帮助安装MySQL绑定Ruby

从[这里][1]下载连接器C文件。(https://downloads.mysql.com/archives/c-c/) 将文件解压到一个位置，如C:\ror\mysqlC\mysql-connector-c-6.1.11-winx64\lib 使用这个模板

install mysql2——'——with-mysql-lib="$lib_location"——with-mysql-include="$include_location"'

我的安装位置是lib_location -> C:\ror\mysqlC\mysql-connector-c-6.1.11-winx64\lib

——with-mysql-lib="C:\ror\mysqlC\mysql-connector-c-6.1.11-winx64\lib"——with-mysql-include="C:\ror\mysqlC\mysql-connector-c-6.1.11-winx64\include"'