2021年上半年数据库系统工程师上午真题及答案解析（71-75）

　　2021年上半年数据库系统工程师上午考试已结束，今天课课家小编为大家整理了2021年上半年数据库系统工程师上午真题及答案解析(71-75)。

　　为方便广大考生考后估分对答案，课课家小编特向广大学员和网友搜集整理了2021年上半年数据库系统工程师真题答案，供大家参考。

　　●When we talk about a database, we must differentiate between the database_ (71)_ ,which is the logical design of the database, and the database_ (72) , which is a snapshot of the data in the database at a given instant in time. The concept of a relation corresponds to the programming-language notion of a variable, while the concept of a relation schema corresponds to the programming-language notion of type definition. In general, a relation schema consists of a listof(73)and their corresponding domains. The concept of a relation instance corresponds to the programming-language notion of a value of a (74) . The valueof a given variable may change with time; similarly the contents of a relation instance may change with time as the relation is updated. In contrast, the_ (75) оfa relation does not generally change.

　　(71)A.schema

　　B.instance

　　C.table

　　D.entity

　　(72)A.schema

　　B.table

　　C.instance

　　D.entity

　　(73)

　　A.variable

　　B.attributes

　　C.rows

　　D.notions

　　(74)A.constant

　　B.variable

　　C.struct

　　D.array

　　(75)A.table

　　B.schema

　　C.instance

　　D.view

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