对于机械安全防护装置的一般要求描述错误的是____．A．结构简单、布局合理 B．有一定的强度、刚度、

A、Relational database model

B、Object-oriented database model

C、Object-relational database model

D、Nonstructural database model

The relational database model requires the data be(110)through programs that don't rely on the position of the data in the database. This is in direct(111)to the other database mode, where the program has to follow a series of pointers to the data it seeks. A program(112)a relational database simply asks for the data it seeks; the DBMS performs the necessary searches and(113)the information. The(114)on how the search is done are specific to the DBMS and vary from product to product.

A．accessed

B．moved

C．read

D．wrote

The relational database model requires the data be(71)through programs that don't rely on the position of the data in the database. This is in direct(72)to the other database mode, where the program has to follow a series of pointers to the data it seeks. A program(73)a relational database simply asks for the data it seeks; the DBMS performs the necessary searches and(74)the information. The(75)on how the search is done are specific to the DBMS and vary from product to product.

A．accessed

B．moved

C．read

D．wrote

从下面提供的答案中选出应填入下列英文语句中______内的正确答案。

The relational database model requires the data be(1)through programs that don't rely on the position of the data in the database. This is in direct(2)to the other database mode, where the program has to follow a series of pointers to the data it seeks.A program(3)a relational database simply asks for the data it seeks; the DBMS performs the necessary searches and(4)the information. The(5)on how the search is done are specific to the DBMS and vary from product to product.

The relational database model requires the data be(1)through programs that don't rely on the position of the data in the database. This is in direct(2)to the other database mode, where the program has to follow a series of pointers to the data it seeks.A program(3)a relational database simply asks for the data it seeks; the DBMS performs the necessary searches and(4)the information. The(5)on how the search is done are specific to the DBMS and vary from product to product.

What is the candidate key of a relational database？ ()

A．Fields from multiple tables that are used for sorting records

B．A set of fields in a table used to identify a record uniquely

C．A field with a constraint placed on it

D．A set of fields that have no data in them