B. It provides a generic mechanism for storing relationships among the data items.
C. It provides a means to constrain that data to meaningful values as determined by the application.
C. triggers allow user to specify when such checking should occur.
D. A call of a Stored Procedure must be called in one transaction
19. Among the following sentences about transaction state,is wrong.
7.is a minimal set of attributes for which it holds that: no two distinct tuples in the relation can have the same values for the attributes in this set.
华南农业大学期末考试试卷（B卷）
2012学年第一学期考试科目：数据库系统
考试类型：闭卷考试时间：120分钟
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Instructions to candidates:
1.Write your name, student number and class on both thequestionpapersand the answer papers.
A. Select operationB. Cartesian product
C. ProjectionD. Natural join
5. A database is a data collection without the following additional feature
A. database contain both data and metadata, the latter being descriptive data about the raw data.
B. In SQL, a view can be used like a stored relation in any operations.
C. In SQL, the value NULL is ignored in any expression.
D. SQL is a rative query language, in which only what we want must be declared, in formulating a query.
A. an attribute that is a primary key of another table.
B. an attribute that is a primary key of the same table.
C. both a.) and b.) D. neither a.) nor b.).
C.Separation of logical and external levelsD. Conceptual unit of manipulation
14. Stored Procedures
A. Can be executed on database server or application server.
2.DO NOT write your answerson thequestionpapers.Write themALL ON THE ANSWER PAPERS.
3. Write your answers in either Chinese or English. If the answer in English is correct, you can get bonus marks.
18. Among the following sentences about transaction,is wrong.
A. Operations in a Trigger and operation arouses the trigger is in one transaction
B. assertions must be, in principle, checked any time when data is modified
C. structure of data in relational database
D. table used to store information of entity
12. Which of the following is not correct?
A. database instance is a snapshot of database
D. It provides a uniform service interface for data maintenance and query activity, such as SQL in the case of the relational model.
6. A foreign key can make reference to
A. a table consisting of a set of rows (or tuples) that have the same attributes.
B. a table that can have sub-tables used to store information about components.
13. Physical data independence means
A.Ensures that conceptual schema does not have to change when physical storage is reorganizedB.A framework for facts
3.Hand inallpapers (both thequestionpapersand the answer papers).
Question 1 [45 marks, 1.5 marks for each.]:Single choice questions，select the most appropriate answer please.
A. Schema normalization not only reduces potential data redundancy but also enhances query efficiency.
B. A schema in 3NF will be in BCNF as well.
C. If A→B and C→D hold, then AC→BD also holds.
1. A data model consists of
A. schemaB. set of operations
C. set of constraintsD. all of A, B, and C
2. The Entity-Relationship data model is
A. DBMS dependent.B. DBMS independent.
B. is a subroutine available to applications that access a relational database system
C. is just the same as Stored Function
D. A Stored Procedure is a transaction that must be treated as a whole.
C. loss of spurious tuples during the join operation. D. loss of join path.
10. If there is a one-to-one relationship between entity A and B, then
A. there exists a functional dependency from the primary key in B to the primary key in A, i.e., PK(B)®PK(A).
D. If A→C and BC→D hold, then AC→BD also holds.
17. In the follows,is correct
A. For any SQL query, there exists a unique translation into relation algebra.
C. both A and BD. neither A nor B
3. A key in a database table is
A. minimal superkeyB. a proper superset of a candidate key.
C. proper subset of a candidate keyD. neither a.) nor b.)
B. there exists a functional dependency from the primary key in A to the primary key in B, i.e., PK(A)®PK(B).
C. both A and B.D. neither A nor B
11. In the context of the Relational model of data, relation means: