First, I browsed through SO for matching questions and didn't find one, but please point me in the right direction if this exact question has already been asked.

I work with and around programmers of various skill levels on various platforms. I would consider my skills to be strong in terms of relational database design, query development, and basic performance tuning and administration. I'm mid-level when it comes to database theory.

My team is looking to me to ensure that we have the best talent on staff, in this case, an engineer experienced in Oracle administration. To me, a well-rounded database administrator, regardless of platform, should also be competent in developing against the database so that is also a requirement.

However my database skills are centralized around SQL Server 200x with experience in a few other products like SAP MaxDB, Access, and FoxPro.

How can I thoroughly assess the skills of an Oracle engineer? I can ask high-level database theory questions and talk about routine tasks that are common across platforms, but I want to dig deep enough that I can be confident in the people I hire. Normally, I would alternate very specific questions that have a right/wrong answer with architectural questions that might have several valid answers.

Does anyone have an interview template, specific questions, or any other knowledge that they can share? Even knowing the meaningful Oracle-related certifications would be a help. Thank you.

EDIT: All the answers have been very helpful so far and I have given upvotes to everyone.

I'm surprised that there are already 3 close votes on this question as "off topic". To be clear, I am specifically asking how a MS SQL Server engineer (like myself) can effectively interview a person with different but symbiotic skills.

The question has already received specific, technical answers which have improved my own database design and programming skills.

If this is more appropriate as a community wiki, please convert it.