dbms

1) What are the drawbacks of the file system which is overcome on the database management system?

1)在数据库管理系统上克服的文件系统有哪些缺点？

Ans: Data redundancy & isolation, difficulty in accessing data, data isolation, and integrity problem these are drawbacks of the file system.

答案：数据冗余和隔离，访问数据困难，数据隔离以及完整性问题是文件系统的缺点。

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2) What is database system?

2)什么是数据库系统？

Ans: The database which is the collection of information and DBMS software together is called database system.

回答：作为信息和DBMS软件的集合的数据库称为数据库系统。

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3) Which level of abstraction describes what data are stored in the database?

3)哪个抽象级别描述了数据库中存储了哪些数据？

Ans: Logical level describes what data are stored in the database.

回答：逻辑级别描述了哪些数据存储在数据库中。

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4) What is view level or external level data hiding?

4)什么是视图级别或外部级别数据隐藏？

Ans: It is the highest level of abstraction that describes only part of the entire database this part implies the interaction of users with the system.

回答：它是最高的抽象级别，仅描述了整个数据库的一部分，这部分意味着用户与系统的交互。

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5) Why is the entity set called weak entity set?

5)为什么将实体集称为弱实体集？

Ans: The entity set is called weak entity set because it does not have the primary key.

回答：实体集称为弱实体集，因为它没有主键。

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6) What are the extended features of ER diagram?

6)ER图的扩展功能是什么？

Ans: Specialization, generalization, aggregation are the extended features of ER diagram.

回答：专业化，通用化，聚合是ER图的扩展功能。

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7) How many types of relationship exist in database designing?

7)数据库设计中存在几种类型的关系？

Ans: There are three major relationship models,

答：有三种主要的关系模型，

1. One- to- one

   一对一

2. One- to- many

   一对多

3. Many- to- many

   多对多

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8) What is the minimum cardinality of zero specifies?

8)零的最小基数是多少？

Ans: Partial participation is the minimum cardinality of zero specifies.

回答：部分参与是指定的最小基数为零。

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9) When the fan trap may exist in ER model.

9)ER模型中可能存在风扇陷阱。

Ans: When two or more one to more relationships fan out from the same entity set then the fan trap may exist in ER model.

回答：当两个或多个一对一关系从同一实体集中散开时，则扇形陷阱可能存在于ER模型中。

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10) What is RAT axioms in DBMS?

10)DBMS中的RAT公理是什么？

Reflexivity, argumentation, transitivity these are the Armstrong rule which is sufficient enough to find closure set.

自反性，论据，传递性是阿姆斯特朗规则，足以找到闭合集。

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11) What are database languages?

11)什么是数据库语言？

Ans: These are the special purpose languages in DBMS. It is of three types of DDL (data definition language), DML (data manipulation language, a query language.

回答：这些是DBMS中的专用语言。 它具有DDL(数据定义语言)，DML(数据操作语言，查询语言)三种类型。

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12) What is meant by index cardinality?

12)索引基数是什么意思？

Ans: Index cardinality is the total number of distinct key values for each index.

答案：索引基数是每个索引的不同键值的总数。

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13) What is the foreign key?

13)什么是外键？

The attribute of one table which is referencing the primary key of other table is called foreign key.

一个表的属性引用另一个表的主键称为外键。

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14) What is prime attribute of the relational schema?

14)关系模式的主要属性是什么？

Ans: An attribute is called prime attribute when it is the part of any candidate key in the relational schema.

回答：当属性是关系模式中任何候选键的一部分时，该属性称为主要属性。

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15) How many types of normal form in normalization?

15)规范化中有几种类型的规范形式？

There are mainly four types of normal form,

范式主要有四种类型，

1. 1 NF (first normal form)

   1 NF(第一个范式)

2. 2 NF (second normal form)

   2 NF(第二范式)

3. 3 NF (third normal form)

   3 NF(第三范式)

4. BCNF (Boyee-Codd normal form)

   BCNF(Boyee-Codd正常形式)

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16) What is the full form of PGNF?

16)PGNF的完整形式是什么？

The full form of PGNF has projected join normal form it is the 5 the normal form and it cannot have a lossless decomposition into any number of smaller tables.

PGNF的完整形式已预测联接普通形式，它是普通形式的5，并且不能无损地分解成任意数量的较小表。

17) What is RDBMS?

17)什么是RDBMS？

Relational database management system (RDBMS) is the database management system that maintains data records and indices in tables

关系数据库管理系统(RDBMS)是一种数据库管理系统，用于维护表中的数据记录和索引

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18) What is chasm trap?

18)什么是陷阱？

Ans: When the two relations are interconnected through partial participation by another relation then it is called chasm trap.

回答：当两个关系通过另一个关系的部分参与而相互连接时，则称为鸿沟陷阱。

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19) What is a transaction in DBMS?

19)什么是DBMS中的事务？

Ans: A transaction is a logical unit of database processing that includes one or more database access operations.

回答：事务是数据库处理的逻辑单元，包括一个或多个数据库访问操作。

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20) Which property makes transaction consistent?

20)哪个属性可使交易保持一致？

Ans: The transaction should possess several properties called ACID property,

回答：交易应具有几个称为ACID属性的属性，

1. A- Atomicity

   A-原子性

2. C – Consistency

   C –一致性

3. I – isolation

   我–隔离

4. D – Durability

   D –耐久性

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21) What are the different phases of the transaction?

21)交易有哪些不同阶段？

Ans: There are three different phases of the transaction. Analysis phase, Redo phase, Undo phase.

回答：交易分为三个不同阶段。 分析阶段，重做阶段，撤消阶段。

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22) What are the Transaction states?

22)什么是交易状态？

Ans: A transaction moves from one state to the other as it entries the system to be executed. There are many states like active, partially committed, failed, Aborted, committed.

答：事务在进入要执行的系统时会从一种状态转移到另一种状态。 有许多状态，例如活跃，部分承诺，失败，中止，承诺。

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23) What is concurrency?

23)什么是并发？

Ans: Concurrency is the ability of the database system to handle simultaneously a number of transactions by overlapping or interleaving parts of their actions.

回答：并发是数据库系统通过重叠或交错部分操作来同时处理多个事务的能力。

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24) What is the common problem that happens due to concurrency?

24)由于并发发生的常见问题是什么？

Ans: There are many common problems,

答：有很多常见问题，

• Dirty read problem

  脏读问题

• Loss update problem

  损失更新问题

• Unrepeatable read problem

  不可重复的阅读问题

• Phantom read problem

  幻影读取问题

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25) What is read timestamp?

25)什么是读取时间戳？

Ans: It is the timestamp of the transaction that has performed latest read operations.

回答：是执行最新读取操作的事务的时间戳。

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26) What is SQL?

26)什么是SQL？

Ans: SQL stands for (structured query language). It is a standard computer language for accessing and manipulating database systems. It is also used to retrieve and update data in a database.

回答： SQL代表(结构化查询语言)。 它是用于访问和操纵数据库系统的标准计算机语言。 它还用于检索和更新数据库中的数据。

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27) What is scheduling?

27)什么是排程？

Ans: A schedule contains two or more transactions executed together or one after another.

回答：计划包含两个或多个一起执行的事务或一个接一个地执行。

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28) How can the schedule be classified?

28)时间表如何分类？

Ans: A schedule can be classified in mainly two ways,

回答：时间表主要可以通过两种方式分类：

1. On the basis of serializability

   基于可序列化

2. On the basis of recoverability

   基于可恢复性

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29) What are blind writes?

29)什么是盲写？

Ans: When the update occurs without knowing or accessing previous value of data items are called blind updation or blind writes.

回答：如果在不知道或无法访问数据项先前值的情况下进行更新，则称为盲更新或盲写。

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30) What are the various methods of concurrency control?

30)并发控制有哪些各种方法？

Ans: There are various concurrency control techniques like Time stamping protocol, Locked based protocol, Optimistic concurrency.

回答：有多种并发控制技术，例如时间戳协议，基于锁定的协议，乐观并发。

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31) What is the trigger?

31)触发因素是什么？

Ans: A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE, or UPDATE) occurs.

回答：触发器是一个SQL过程，当事件(INSERT，DELETE或UPDATE)发生时，该触发器将启动操作。

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32) Which level of locking provides more concurrency in a relational database?

32)哪种级别的锁定可在关系数据库中提供更多的并发性？

Ans: Row-level provides the highest degree of concurrency in a relational database.

回答：行级在关系数据库中提供了最高的并发度。

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33) What is VDL?

33)什么是VDL？

Ans: VDL is view definition language which specifies user’s views and their mapping to the conceptual schema.

回答： VDL是视图定义语言，它指定用户的视图及其到概念架构的映射。

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34) What is a checkpoint?

34)什么是检查站？

Ans: A checkpoint is like a snapshot of the DBMS state. By taking checkpoint the DBMS can reduce the amount of work to be done during restart.

回答：检查点就像是DBMS状态的快照。 通过使用检查点，DBMS可以减少重新启动期间要完成的工作量。

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35) What is Deadlock?

35)什么是死锁？

Ans: Deadlock occurs when two transactions are each waiting on a resource that the other transaction holds.

回答：当两个事务都在等待另一个事务所拥有的资源时，就会发生死锁。

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36) What is the use of DBCC Command?

36)DBCC命令的用途是什么？

Ans: DBCC stands for database consistency checker. We use these commands to check the consistency of the database.

回答： DBCC代表数据库一致性检查器。 我们使用这些命令来检查数据库的一致性。

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37) What is Thomas write rule?

37)什么是托马斯写规则？

Ans: In Thomas write rule we suggest a modification in time stamping protocol when the attempt writes request.

回答：在Thomas写规则中，我们建议在尝试写请求时修改时间戳协议。

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38) What is the recoverable schedule?

38)什么是可恢复时间表？

Ans: A schedule is said to be recoverable if in case of failure the dependent schedule has a chance of rollback.

回答：如果从属日程表有回退的机会，则日程表可以恢复。

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39) What is cascading rollback?

39)什么是级联回滚？

Ans: It is the phenomenon in which a single transaction failure leads to a series of transaction rollbacks it is called cascading rollback.

回答：这种现象是单个事务失败导致一系列事务回滚，称为级联回滚。

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40) What are instances?

40)什么是实例？

Ans: The collection of information stored in the database at a particular moment is called instances.

回答：在特定时刻存储在数据库中的信息集合称为实例。

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41) In which fields the clustered index is built?

41)聚集索引在哪些字段中构建？

Ans: A clustered index is built on the Ordering non-key field.

回答：聚集索引建立在“订购非关键”字段上。

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42) Why the DBMS uses B and B+ trees for searching?

42)为什么DBMS使用B和B +树进行搜索？

Ans: B and B+ tree keep the height of the tree smaller thus reduce searching time. These trees grow horizontally while other AVL, Red black trees grow vertically.

答案： B和B +树使树的高度变小，从而减少了搜索时间。 这些树水平生长，而其他AVL，红黑树垂直生长。

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43) Why are B+ trees preferred over B tree?

43)为什么B +树比B树更受青睐？

Ans: The B+ tree is suitable for sequential and direct access. B+ tree height is less than that of B tree and all leaf nodes are at same level.

答案： B +树适用于顺序访问和直接访问。 B +树的高度小于B树的高度，并且所有叶节点处于同一水平。

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44) What is view?

44)什么是视图？

Ans: A view may be a subset of a database or it may contain virtual data that is stored in the database files but is not explicitly stored.

回答：视图可能是数据库的子集，或者它可能包含存储在数据库文件中但未明确存储的虚拟数据。

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45) What are important pieces of RDBMS architecture?

45)RDBMS体系结构的重要部分是什么？

Ans: There are two important pieces of RDBMS first is kernel which is the software and other is data directory which consists of system level data structure.

回答： RDBMS有两个重要的部分，首先是内核，这是软件，而另一个是数据目录，它由系统级数据结构组成。

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46) How can we communicate with an RDBMS?

46)我们如何与RDBMS通信？

Ans: We can communicate with an RDBMS using SQL (structured query language).

回答：我们可以使用SQL(结构化查询语言)与RDBMS进行通信。

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47) What is a catalog?

47)什么是目录？

Ans: A catalog is a table that consists the information such as the structure of each file, type, and storage format for each data item. The information stored in the catalog is called Metadata.

回答：目录是一个表，包含诸如每个数据项的每个文件的结构，类型和存储格式之类的信息。 目录中存储的信息称为元数据。

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48) What is the order of clause?

48)子句的顺序是什么？

Ans: ORDER by clause helps us to sort the data by ascending order or descending order.

回答： ORDER by子句可帮助我们按升序或降序对数据进行排序。

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49) What is Phantom read problem?

49)什么是幻影读取问题？

Ans: In phantom read problem, a transaction cannot repeat its read instruction because that variable is deleted by some other instruction.

回答：在幻像读取问题中，事务无法重复其读取指令，因为该变量已被其他指令删除。

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50) What is join?

50)什么是加入？

Ans: Joins helps in explaining the relationship between different tables. There are of two types – INNER JOIN and OUTER JOIN.

答案：联接有助于解释不同表之间的关系。 有两种类型-INNER JOIN和OUTER JOIN。

I hope you will like these DBMS Interview questions and answers, if you feel any difficulty in any question please write in the comment box.

我希望您会喜欢这些DBMS面试问题和答案 ，如果您对任何问题有任何困难，请在评论框中写下。

翻译自: https://www.includehelp.com/dbms/top-50-dbms-interview-questions-and-answers.aspx

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