Where can I learn the basics about string processing in RDBMSs?

Hi,

I'm dissecting databases at the moment, and I've started to implement
my own just to get the proper understanding of things. To continue
from where I am right now I need to learn about string processing used
in todays RDBMSs. Issues I need to get the hang of are such as:
- Indexing techniques
- Searching and sorting
- UNICODE (I plan to use ICU)

I need to know the basics, and the tricks and trades of the field
before I start to read source code.

Hopefully someone here can help me gather the information I need.

Thanks!
/Sune