Concrete5 will not install on anything but an empty database and will not prefix tables, so you can't add it on top of an existing database.

If you can prefix the existing database, or if none of its tables conflict with c5 tables, you may be able to

- backup and export existing database
- scrub the database
- install c5
- import the exported database on top of the c5 database

If there are no conflicting table names, it may work.

If there are are conflicting table names, everything will break and the best you will be able to do is scrub again and restore your existing database.

A much easier solution would be to use a different web host. One that allows multiple databases.

Good idea, but it is not so convenient, at least we should have possibility to install on existing database. There will be not conflict with tables names in my case, because all other tables I have, are prefixed.
The problem is that it is working site and I do not want it down for long time.
Is there any plans for adding prefixes in the future conrete5 releases?
This limitation of the concrete5 make people to choose another CMS. Most of the web hotels I know, are giving you one database with unlimited number of tables.

Thanks

RafaelA

You can play the same kind of trick the other way round.

Install c5 elsewhere, then copy all the files to your live site, update config/site.php to match, and copy the c5 database tables into your existing database.

Its a dodgy practice and subject to all the same risk as the previous hack.