The Qlikview Certification is bit difficult, it is not that much easier. For clearing this exam you should have practical knowledge, like designing data model, scripting, designing dashboards etc. You should have thorough working knowledge. All the questions are scenario based.
As Sunil said you should also have knowledge Datawarehousing concepts like schemas, Dimensions and Measures. Set Analysis and scripting is also the important one, based on that many questions will be asked. Also you can expect 3 to 5 questions based on data modeling and data.