windows搭建rails环境中，mysql2 gem 安装error问题

windows搭建rails环境中，mysql2 gem 安装error问题

可以尝试使用下面几种方法:

1. Uninstalling and reinstalling the gem will often solve this issue with no need to download and move files around by hand. From your rails app directory:

> gem uninstall mysql2

You have requested to uninstall the gem:
    mysql2-0.3.11
database_cleaner-0.9.1 depends on [mysql2 (>= 0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn]  Y
Successfully uninstalled mysql2-0.3.11

> bundle install

Fetching gem metadata from http://rubygems.org/......
Fetching gem metadata from http://rubygems.org/..
Using rake (0.9.2)
Using i18n (0.6.1)
... <SNIP> ...
Installing mysql2 (0.3.11) with native extensions
... <SNIP> ...
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

2. 

I had the same problem as you, or at least the symptom was the same.

Background: I was using Rails 3, the mysql2 gem, and MySQL community server version 5.5.21 (32-bit) installed locally on my Windows machine. I grabbed the client library (libmysql.dll) from the MySQL installation and copied it to my ruby installation's bin folder.

When I ran bundle exec rake db:create, I got the same error message as you and I thought "Hey, how can the client library be outdated when I got it from the latest MySQL release?"

There's a helpful message that is shown when you gem install mysql2. Unfortunately, if you install the gem with Bundler, Bundler eats the message. Here it is:

=========================================================================
You've installed the binary version of mysql2. It was built using MySQL 
Connector/C version 6.0.2. It's recommended to use the exact same version
to avoid potential issues.

At the time of building this gem, the necessary DLL files where available
in the following download:

http://dev.mysql.com/get/Downloads/Connector-C/mysql-connector-c-noinstall-6.0.2-win32.zip/from/pick

And put lib\libmysql.dll file in your Ruby bin directory, for example
C:\Ruby\bin

3. 

If you are using 64bit version of mysql and 32bit version of ruby, then check this solution on http://blog.mmediasys.com/2011/07/07/installing-mysql-on-windows-7-x64-and-using-ruby-with-it/

You basically have to download a single connector from mysql website, and compile mysql or mysql2 with connector you downloaded.

for Ruby 1.9.2:

gem install mysql --platform=ruby -- --with-mysql-dir=C:/mysql-connector-c-noinstall-6.0.2-win32

for Ruby 1.9.3: (showing mysql2 variant)

gem pristine mysql2 -- --with-mysql-config=C:\mysql-connector-c-noinstall-6.0.2-win32   

Note the use of forward slashes for the directory where MySQL Connector/C was extracted.