数据库系统期末试题及答案.docx

1. A primary key is a field (or group of fields) that uniquely describes each record in

the database.

2. Data redundancy improves the integrity of a database.

3. SQL is the language used by relational databases to create objects and to

manipulate and retrieve data.

4. A relational database management system does not include tools for backing up &

restoring databases.

5. An attribute is also known as a row in most databases.

10. Most relationship sets in a database system involves two entity sets.

11. The closure of an attribute set contains that attribute set.

12. Lossless decomposition is necessary in a decomposition algorithm.

14. It is not necessary that a legal schedule preserves the order in which the

instructions appear in each individual transaction.

15. Update operations in database must be written into log before updating database.

1. is the only one incorrect description from the followings: