mysql-server:取决于:mysql-server-5.5但是不会安装它

我在VirtualBox上使用ubuntu 14.04.我尝试使用命令sudo apt-get install mysql-server安装mysql-server,我总是得到如下错误:

Some packages could be installed .This may mean that you have 
request an impossible  situation or if you are using the unstable
distribution that some required packages have not yet been created 
or been moved out of Incoming.
The following packages have unmet dependencies:
mysqsl-server : Depends: mysql-server-5.5 but it is not going to be installed
E:Unable to correct problems, you have held broken packages.

然后我尝试使用如下命令:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get purge mysql-server*
sudo apt-get install mysql-server

但它仍然是错误的.请帮我!