When trying to install mysql-simple on GHC 7.8.3 with cabal on Ubuntu Linux 12.04, the mysql dependency failed with the following error:

mysql- failed during the configure step. The exception was:
ExitFailure 1
mysql-simple- depends on mysql- which failed to install.

A quick SO lead me to the solution. I needed to install the mysql-client library on linux:

sudo apt-get install libmysqlclient-dev

Enjoy! :)