精选优质文档-倾情为你奉上Exam of Database Technology & Applications 1. Describe the three levels and data independence.2. What are key constraints and foreign constraints?3. Explain LEFT JOIN, OUTER JOIN and INNER JOIN.4. For the following relation schema and sets of FDs: R is (A, B, C, D, E, F,G) with FDs A- B, B- C, A- E, CD-G.1) Identify the candidate key(s) for R.2) Identify the best normal form that R satisfies3) Decompos
