I would start by asking the developer if he/she can tell me about the major classes that make up JDBC. You should hear something about Connection, Statement, PreparedStatement, CallableStatement, ResultSet, etc.
Ask about what things you need to be concerned with in JDBC programs when exceptions occur. I'd want to hear about how resources such as PreparedStatements and ResultSets are dealt with. These should typically go in a "finally" block, which gets executed just before the method returns, or after specific exception handling is executed.
You might want to ask about how Connections are opened and closed (and how often). Maybe how connection pooling is typically implemented (wrapping of JDBC classes etc).
If some Oracle expertise is claimed, try to get an explanation of the various JDBC drivers that Oracle offers (i.e. Thin, OCI, internal). Also ask for an explanation of Oracle's consistency model. And, how to determine where execution time is being spent (tracing etc).
If they think they are good with SQL, Tom Kyte had an interesting set of (3) questions to ask, in exponentially increasing difficulty. If I may be so bold as to paraphrase my recollection of it here (HTML follows...):
*_SQL Test_*
Let's say we have a simple table called "purchases", defined as follows:
/PURCHASES/
*CUSTOMER_ID*
*NUMBER*
*PURCHASE_DATE*
*DATE*
AMOUNT
NUMBER
Primary Key columns are shown in bold.
Can you write the SQL for the following questions?
*_Q1: _* How many records are in the PURCHASES table? *_Q2:_* Produce a summarized list of purchases (number and total amount) by month. *_Q3:_* For each month, which customer had the highest number of purchases? --Peter
