Recommended way of adding prefixes to the String keys(row keys) to be stored in database

What is the recommended way in Java to add prefixes to String keys to be s开发者_StackOverflow中文版tored in database of a web application?

I have an EntityId per Entity but I want to store different kinds of data for an Entity, in different rows distinguished by prefixed EntityId keys like this format: EntityId | PrefixForThisDataCategory

In general, databases resist that kind of thing. They're happy to store "prefix" characters in a separate column, though. If that column needs to be part of a composite key, they're happy to do that, too.

But if you want to store different kinds of data in different rows of the same table, I hope I can discourage you. Databases--SQL databases, that is--are designed to keep different kinds of data in different tables. People in one table, addresses in another table . . . not addresses in some rows of a table of people.

Of course, you might be aiming at something completely different.

If I understand your question correctly you basically want to store data representing different sets of information in a common table and use one or more fields to differentiate what type of data has been stored.

THIS IS A REALLY BAD IDEA ! - had to say it :-)

I can tell you from experience on many projects that storing data in this way always leads to problems and really messy code. My strong recommendation would be to store the data is separate tables.

There is one variation I can think of however, that is similar to your request, that is derived class mapping in hibernate. There hibernate maps sets of data into tables based on the class that is being stored. This is only for mapping hierarchies of classes and is controlled by hibernate so that you don't have to worry about it.