数据库的并发操作可能带来的问题包括（ ）
在数据库运行阶段，如果频繁访问两个表中的关联数据，则考虑采用__61__的方法：如果表中元组数量很大，导致操作效率降低，在不修改程序和表逻辑模式的情况下，可以考虑采用__62__的方法。
Ravi, like many project （ ） , had studied the waterfall model of software development as the primary software life-cycle （ ） . He was all set to use it for an upcoming project, his first assignment. However, Ravi found that the waterfall model could not be used because the customer wanted the software delivered in stages, something that implied that the system had to be delivered and built in （ ） and not as （ ） 。The situation in many other projects is not very different. The real world rarely presents a problem in which a standard process, or the process used in a previous project, is the best choice. To be the most suitable, an existing process must be （ ） to the new problem.A development process, even after tailoring, generally cannot handle change requests. To accommodate change requests without losing control of the project, you must supplement the development process with a requirement change management process.
算术表达式采用逆波兰式表示时不用括号，可以利用（ ）进行求值。与逆波兰式ab-cd+*对应的中缀表达式是（ ）。
Ravi, like many project （ ） , had studied the waterfall model of software development as the primary software life-cycle （ ） . He was all set to use it for an upcoming project, his first assignment. However, Ravi found that the waterfall model could not be used because the customer wanted the software delivered in stages, something that implied that the system had to be delivered and built in （ ） and not as （ ） 。The situation in many other projects is not very different. The real world rarely presents a problem in which a standard process, or the process used in a previous project, is the best choice. To be the most suitable, an existing process must be （ ） to the new problem.A development process, even after tailoring, generally cannot handle change requests. To accommodate change requests without losing control of the project, you must supplement the development process with a requirement change management process.
对于逻辑表达式“x and y or not z”，and、or、not分别是逻辑与、或、非运算，优先级从高到低为not、and、or,and、or为左结合，not为右结合，若进行短路计算，则（)。
网络配置如图所示，其中使用了一台路由器、一台交换机和一台集线器，对于这种配置，下面的论断中正确的是（ ）。
通过将一个关系拆分成两个更小的关系来使其满足范式时，必须（ ）来保持数据的完整性约束。
对于不包含子查询的SELECT语句，聚集函数不允许出现的位置是（ ）。
在UML图中，__27__展现了一组对象、接口、协作和它们之间的关系；__28__展现了运行处理节点及其构件的配置，给出了体系结构的静态实施视图。
假设有关系E（学校名称，所在地）和F（学校名称，专业代码，分数线），查询所有学校所有专业的分数线，以及学校所在地的信息，对应的关系表达式为（）。
Ravi, like many project （ ） , had studied the waterfall model of software development as the primary software life-cycle （ ） . He was all set to use it for an upcoming project, his first assignment. However, Ravi found that the waterfall model could not be used because the customer wanted the software delivered in stages, something that implied that the system had to be delivered and built in （ ） and not as （ ） 。The situation in many other projects is not very different. The real world rarely presents a problem in which a standard process, or the process used in a previous project, is the best choice. To be the most suitable, an existing process must be （ ） to the new problem.A development process, even after tailoring, generally cannot handle change requests. To accommodate change requests without losing control of the project, you must supplement the development process with a requirement change management process.
单选题When we talk about a database, we must differentiate between the database,which is the logical design of the database, and the database ， which is a snapshot of the data in the database at a given in
单选题在程序设计语言中， 表示了构成语言的各个记号和使用者的关系，而语境是指理解和实现程序设计语言的环境，包括请填写此空 环境和运行环境。
单选题某公司的数据库在试运行阶段发现cpu长时间占用率高于95%，那么不可能的原因是 。在运行一段时间后，由于硬盘故障，该数据库无法运行，这属于请填写此空 。
单选题假设有两个数据库表isurance和epoeer分别记录了某地所有工作人员的社保信息和基本信息:insurance id, is valid,各属性分别表示身份证号，社保是否有效，其中is _valid=1表示社保有效，is valid=0表示社保无效。employee id, name, salay, is local, 各属性分别表示身份证号，姓名，每月工资，户口是否在当地，其中is_ loc
单选题某公司的数据库在试运行阶段发现cpu长时间占用率高于95%，那么不可能的原因是 请填写此空 。在运行一段时间后，由于硬盘故障，该数据库无法运行，这属于 。
单选题相比于文件系统，用数据库系统管理数据，具有的优势。
单选题下表是某两个事务并发执行时的调度过程，这里不会出现不可重复读的问题，是因为这两个事务都使用了(请填写此空);两个事务的并行执行结果是正确的，是因为这两个事务都使用了();在执行过程中没有发生死锁，这是因为()导致的。
单选题要求关系模式的属性之间不允许有非平凡且非函数依赖的多值依赖的是（）。