In godaddy, I am trying to install magento corresponding to my main domain www.shoppox.com and simultaneously wordpress corresponding to my subdomain blog.shoppox.com.
Could I do this if I have already purchased a hosting plan with single database because each one is requiring a separate database ?
Please suggest a way out (I don't want to spend more in upgrading my hosting plan).
Yes Of course you can, while installing magento, on the installation screen where it asks for the db credentials here is a field named "Tables Prefixes", add a prefix for magento and it will up and running without any problem.
You can install both with same database you have to add prefix to tables name
E.g. Database name : your database name
Password : your password
These credentials will be Used for both . When you install both these is option to add prefix to tables so you just add prefix (magento ,Wordpress) whatever you want
