SQLException. It is just about always thrown when database problems occur. getErrorCode() will give you vendor-specific error code which then you can cross-reference in the manual for the exact problem. in some cases, drivers are so nice with constraint violations that they will give you the exact violation in the message of the exception (getMessage() return) but most of the time you will have to consult the manual and use db software to get the exact cause (that is if there are many constraint violations that can occur on a execution of a single statement).