dbms_排名前50位的DBMS面試問答

dbms

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

1)在數據庫管理系統上克服的文件系統有哪些缺點？

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

答案：數據冗余和隔離，訪問數據困難，數據隔離以及完整性問題是文件系統的缺點。

2) What is database system?

2)什么是數據庫系統？

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

回答：作為信息和DBMS軟件的集合的數據庫稱為數據庫系統。

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

3)哪個抽象級別描述了數據庫中存儲了哪些數據？

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

回答：邏輯級別描述了哪些數據存儲在數據庫中。

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

4)什么是視圖級別或外部級別數據隱藏？

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：它是最高的抽象級別，僅描述了整個數據庫的一部分，這部分意味著用戶與系統的交互。

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

5)為什么將實體集稱為弱實體集？

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

回答：實體集稱為弱實體集，因為它沒有主鍵。

6) What are the extended features of ER diagram?

6)ER圖的擴展功能是什么？

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

回答：專業化，通用化，聚合是ER圖的擴展功能。

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

7)數據庫設計中存在幾種類型的關系？

Ans: There are three major relationship models,

答：有三種主要的關系模型，

One- to- one
一對一
One- to- many
一對多
Many- to- many
多對多

8) What is the minimum cardinality of zero specifies?

8)零的最小基數是多少？

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

回答：部分參與是指定的最小基數為零。

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

9)ER模型中可能存在風扇陷阱。

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：當兩個或多個一對一關系從同一實體集中散開時，則扇形陷阱可能存在于ER模型中。

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，論據，傳遞性是阿姆斯特朗規則，足以找到閉合集。

11) What are database languages?

11)什么是數據庫語言？

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：這些是DBMS中的專用語言。它具有DDL(數據定義語言)，DML(數據操作語言，查詢語言)三種類型。

12) What is meant by index cardinality?

12)索引基數是什么意思？

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

答案：索引基數是每個索引的不同鍵值的總數。

13) What is the foreign key?

13)什么是外鍵？

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

一個表的屬性引用另一個表的主鍵稱為外鍵。

14) What is prime attribute of the relational schema?

14)關系模式的主要屬性是什么？

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

回答：當屬性是關系模式中任何候選鍵的一部分時，該屬性稱為主要屬性。

15) How many types of normal form in normalization?

15)規范化中有幾種類型的規范形式？

There are mainly four types of normal form,

范式主要有四種類型，

1 NF (first normal form)
1 NF(第一個范式)
2 NF (second normal form)
2 NF(第二范式)
3 NF (third normal form)
3 NF(第三范式)
BCNF (Boyee-Codd normal form)
BCNF(Boyee-Codd正常形式)

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的完整形式已預測聯接普通形式，它是普通形式的5，并且不能無損地分解成任意數量的較小表。

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

關系數據庫管理系統(RDBMS)是一種數據庫管理系統，用于維護表中的數據記錄和索引

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：當兩個關系通過另一個關系的部分參與而相互連接時，則稱為鴻溝陷阱。

19) What is a transaction in DBMS?

19)什么是DBMS中的事務？

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

回答：事務是數據庫處理的邏輯單元，包括一個或多個數據庫訪問操作。

20) Which property makes transaction consistent?

20)哪個屬性可使交易保持一致？

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

回答：交易應具有幾個稱為ACID屬性的屬性，

A- Atomicity
A-原子性
C – Consistency
C –一致性
I – isolation
我–隔離
D – Durability
D –耐久性

21) What are the different phases of the transaction?

21)交易有哪些不同階段？

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

回答：交易分為三個不同階段。分析階段，重做階段，撤消階段。

22) What are the Transaction states?

22)什么是交易狀態？

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：事務在進入要執行的系統時會從一種狀態轉移到另一種狀態。有許多狀態，例如活躍，部分承諾，失敗，中止，承諾。

23) What is concurrency?

23)什么是并發？

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：并發是數據庫系統通過重疊或交錯部分操作來同時處理多個事務的能力。

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

24)由于并發發生的常見問題是什么？

Ans: There are many common problems,

答：有很多常見問題，

Dirty read problem
臟讀問題
Loss update problem
損失更新問題
Unrepeatable read problem
不可重復的閱讀問題
Phantom read problem
幻影讀取問題

25) What is read timestamp?

25)什么是讀取時間戳？

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

回答：是執行最新讀取操作的事務的時間戳。

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(結構化查詢語言)。它是用于訪問和操縱數據庫系統的標準計算機語言。它還用于檢索和更新數據庫中的數據。

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：計劃包含兩個或多個一起執行的事務或一個接一個地執行。

28) How can the schedule be classified?

28)時間表如何分類？

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

回答：時間表主要可以通過兩種方式分類：

On the basis of serializability
基于可序列化
On the basis of recoverability
基于可恢復性

29) What are blind writes?

29)什么是盲寫？

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

回答：如果在不知道或無法訪問數據項先前值的情況下進行更新，則稱為盲更新或盲寫。

30) What are the various methods of concurrency control?

30)并發控制有哪些各種方法？

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

回答：有多種并發控制技術，例如時間戳協議，基于鎖定的協議，樂觀并發。

31) What is the trigger?

31)觸發因素是什么？

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

回答：觸發器是一個SQL過程，當事件(INSERT，DELETE或UPDATE)發生時，該觸發器將啟動操作。

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

32)哪種級別的鎖定可在關系數據庫中提供更多的并發性？

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

回答：行級在關系數據庫中提供了最高的并發度。

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是視圖定義語言，它指定用戶的視圖及其到概念架構的映射。

34) What is a checkpoint?

34)什么是檢查站？

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：檢查點就像是DBMS狀態的快照。通過使用檢查點，DBMS可以減少重新啟動期間要完成的工作量。

35) What is Deadlock?

35)什么是死鎖？

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

回答：當兩個事務都在等待另一個事務所擁有的資源時，就會發生死鎖。

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代表數據庫一致性檢查器。我們使用這些命令來檢查數據庫的一致性。

37) What is Thomas write rule?

37)什么是托馬斯寫規則？

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

回答：在Thomas寫規則中，我們建議在嘗試寫請求時修改時間戳協議。

38) What is the recoverable schedule?

38)什么是可恢復時間表？

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

回答：如果從屬日程表有回退的機會，則日程表可以恢復。

39) What is cascading rollback?

39)什么是級聯回滾？

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：這種現象是單個事務失敗導致一系列事務回滾，稱為級聯回滾。

40) What are instances?

40)什么是實例？

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

回答：在特定時刻存儲在數據庫中的信息集合稱為實例。

41) In which fields the clustered index is built?

41)聚集索引在哪些字段中構建？

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

回答：聚集索引建立在“訂購非關鍵”字段上。

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

42)為什么DBMS使用B和B +樹進行搜索？

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 +樹使樹的高度變小，從而減少了搜索時間。這些樹水平生長，而其他AVL，紅黑樹垂直生長。

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

43)為什么B +樹比B樹更受青睞？

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 +樹適用于順序訪問和直接訪問。 B +樹的高度小于B樹的高度，并且所有葉節點處于同一水平。

44) What is view?

44)什么是視圖？

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：視圖可能是數據庫的子集，或者它可能包含存儲在數據庫文件中但未明確存儲的虛擬數據。

45) What are important pieces of RDBMS architecture?

45)RDBMS體系結構的重要部分是什么？

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有兩個重要的部分，首先是內核，這是軟件，而另一個是數據目錄，它由系統級數據結構組成。

46) How can we communicate with an RDBMS?

46)我們如何與RDBMS通信？

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

回答：我們可以使用SQL(結構化查詢語言)與RDBMS進行通信。

47) What is a catalog?

47)什么是目錄？

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：目錄是一個表，包含諸如每個數據項的每個文件的結構，類型和存儲格式之類的信息。目錄中存儲的信息稱為元數據。

48) What is the order of clause?

48)子句的順序是什么？

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

回答： ORDER by子句可幫助我們按升序或降序對數據進行排序。

49) What is Phantom read problem?

49)什么是幻影讀取問題？

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

回答：在幻像讀取問題中，事務無法重復其讀取指令，因為該變量已被其他指令刪除。

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.