201112数据库原理复习资料.doc

习题1 Blank-filling questions in DBS situation.（2 marks × 15 = 30 marks） 1、To illustrate the concept of a data model, we outline two data models in this section : the _________________ model and the _____________ model. 2、Since many database-systems users are not computer trained, developers hide the complexity from users through several levels of abstraction, to simplify users’ interactions with the system:________ level, _______ level and view level. 3、A database-management system is a collection of interrelated _________ and a set of ________ to access those data. 4、Data model is a collection of conceptual tools for describing _________, ___________________, ____________________, and consistency constraints. 5、A ________ is a virtual relation which is made visible to a user in. 6、A ________ is organized logically as a sequence of records. 7、There are four different types of database-system users：_______________, _________________, sophisticated users and specialized users. 8、A _____________ is a unit of program execution that accesses and possibly updates various data items. 9、A data _________ is a file that stores metadata about the structure of the database. Briefly-answer questions. ( 5 marks × 4 = 20 marks) 1、Here is an authorization graph. List the users who still have authorization after only edge m is moved. List the users who still have authorization after only edge l is moved. 2、Please list the five duties of a database administrator. 3、Please give the definition of “trigger” in database system. 4、Explain the distinctions among the terms superkey, candidate key and primary key. Complete the following queries using relational algebra expressions. ( 4 marks × 3 = 12 marks) Consider the relational database of a banking enterprise with the following relation schemas, where the primary keys are underlined. branch (branch_name, branch_city, assets) customer (customer_name, customer_street, customer_city) loan (loan_number, branch_name,