mysql2 gem compiled for wrong mysql client library

When try to connect to the mysql server through my rails application, I get the following error

D:/Program_Files/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': 
Incorrect MySQL client library version! This gem was compiled for 6.0.0 but the client library is 5.0.27. (RuntimeError)

How can I rectify it?

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.

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ran bundle exec rake db:create, I got the same error message as you and I thought "Hey, how can the client library be outdated when I got it from the latest MySQL release?"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

Following these instructions solved the problem for me.

Referenced link

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.

I had an issue just like this:

Incorrect MySQL client library version! This gem was compiled for 5.5.29 but the client library is 5.6.17.

The issue for me was that I had both versions, 5.5.29 and 5.6.17, installed on my machine. I have no idea how. When I bundled it automatically chose the 5.5.29 version. I uninstalled that one and then reinstalled my gem and that fixed the issue.

I discovered a completely different cause for this problem. I had been using the mysql gem. I built the mysql2 gem but I forgot to update my database.yml. With the mysql2 gem, it needs to say:

  development:
    adapter: mysql2

rather than

  development:
    adapter: mysql

The gem built, but I got the error when I next ran rake.

Obvious once you've seen it, but you get the same error message as discussed here!

By the way, the command to build the mysql2 gem on my machine was a bit more complicated than described above:

gem install mysql2 -- --with-mysql-lib="c:\mysql-connector-c-noinstall-6.0.2-win32\lib"  --with-mysql-include="c:\mysql-connector-c-noinstall-6.0.2-win32\include" --with-mysql-dir="c:\mysql-connector-c-noinstall-6.0.2-win32"

To Add to the existing answer. ( windows platform specifically )

Ruby really sucks on top of this. Rails should not actually care about the version of the connector or the mysql version. -- but that's my opinion.

In order to get this **ing thing working, you need 2 things. mysql2 gem and libmysql.dll and you need to match them up in terms of the version. (this caused confusion for me, because I can see the latest connector is 6.x while mysql is only 5.x, how should I match them up)

mysql2 gem. and when you install it you need to specify the connector.

     gem install mysql2 --platform=ruby -- 
     --with-mysql-lib="d:\mysql\lib" --with-mysql-include="d:\mysql\include"

it does not need to be connector downloaded from oracle. all you need is a mysql installation and the lib include folder underneath it. then put the libmysql.dll under railsinstaller bin folder.

if it didn't work to make you install mysql2 gem succesfully => for my case it is because my mysql is too old (why would ruby care that). so I get some latest mysql from oracle. use the lib include libmysql.dll under it. you don't really need to upgrade your database, you can keep it somewhere and continue to use it after you generated the 2 required components

my case: I use a very ancient mysql database and I am unwilling to upgrade it at the moment. so I back that database up and restored it later

in my case on windows, incorrectly copied libmysql.dll from MySQL Server 5.5 directory to ruby200/bin. correct is to copy libmysql.dll from mysql-connector-c-noinstall-6.0.2-win32.

I had the same problem , and I have solved the follows:

1 :: Download the zip the following link: https://dev.mysql.com/downloads/connector/c/

2 :: decompress the file ( libmysql.dll ) in the " Provider" folder of project.

3 :: Volve one to run the command bundle install

and ready , solved !

https://dev.mysql.com/downloads/connector/c/