Data access layer design pattern

I need to build a data access layer and I am looking for the right design pattern.

what I need is:

1. object mapping: it shouldn't be too complicated and not generic.
2. I have a lot of loo开发者_如何学Ck up tables and I need to a good way to load them. I don't care about starting time (when the program starts up), what I care is to minimizing the number of connections to the db and on the other hand not killing the virtual memory.
3. relationships: I have a lot of connected objects which relate to each other and I need a generic way to load as much as relationships as I want.

Number 2(above) is most critical for me. Any suggestions?

Thanks

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It looks like the Facade pattern could be used here.

and maybe the Singleton pattern too.