\nComponents of DBMS [MARCH – 2008]<\/span> (3)
\nAnswer:
\na) databases – database is an organized collection of information.
\nb) Data Definition Language(DDL) – Data Definition Language is used to specify the definitions of Da-tabase Schema. The result of compilation of DDL statements is a set of tables stored in a special file called data dictionary.
\nc) Data Manipulation Language(DML) – It is a language that enable users to access or manipulate data in the database. It also provides interfaces with programming languages.
\nd) Users – users interact with DBMS indirectly via ; application programs or directly via simple query language.<\/p>\n
Question 2. 2) Inconsistency can be avoided: If data redundancy exist, it may lead to data inconsistency. If redun-dancy is removed then inconsistency can be avoided.<\/p>\n 3) Data can be shared: If the computers are connected to a network, the data stored in the database can be shared among several users or programs.<\/p>\n 4) Standards can be enforced: There is a standard BIS (Bureau of Indian Standards) in the field of Gold and ISBN (International Standard Book Number) in the field of publication. Similarly here is also some standards like ANSI(American National Standards Institute), ISO (International Organization for standardization), etc.. For example a filed \u201cName\u201d should have 40 characters is a standard.<\/p>\n 5) Security restrictions can be applied: The database is of great value to a company or Organization. Data security means protection of data against accidental or intentional disclosure or unauthorized destruction or modification by un-authorized persons.<\/p>\n 6) Integrity can be maintained: It ensures that the data entered in the database is correct. The data may contain incorrect information for example a date of birth can be 30\/30\/2001. To avoid this DBMS defines integrity check.<\/p>\n 7) Efficient data access: It stored huge amount of data efficiently and can be retrieved whenever a need arise.<\/p>\n 8) Crash recovery: Sometimes all ora portion of the data is lost when a system crashes. A good DBMS helpsto recover data afterthe system crashed.<\/p>\n Question 3. Question 4. Question 5. Question 6. b) Network Model : It is similar to hierarchical model, but each child record can have more than one parent record. This model eliminates the re-dundancy encountered in the hierarchy model, but it has a high degree of complexity. It was introduced by CODASYL-DBTG in 1971.<\/p>\n c) Relational Model : It is based on the concept introduced by E F Godd. It composed of one or more tables. Here tables are called relations, rows are called tuples and the columns are called at-tributes. It has no data redundancy and complex-ity. So this is the best model.<\/p>\n Question 7. 2) Project: It selects certain columns from the table and discardsthe other columns. It is denoted by the Greek letter n. Question 8. Question 9. 2) Logical level describes what data are stored in the database and what relationships exist among data. Here database is described in terms of simple structures. Records are defined in this level. Programmers work at this level.<\/p>\n 3) View level is the highest level of data abstraction. It is concerned with the way in which the users view the database. It describes only part of the database.<\/p>\n Question 10. Question 11. Record : The collection of related fields is called a record. Ex: The information about a student File: A file is a collection of related records. Ex: The students details of a class.<\/p>\n Question 12. Question 13. Question 14. Question 15. a) To display those tuples from STUDENT relation where total is greater than 90. Question 16. Question 17. Question 18 Question 19. Question 20. Question 21. Question 22. Answer 2. Question 23. Question 24. 2) Logical level describes what data are stored in the database and what relationships exist among data. Here database is described in terms of simple structures. Records are defined in this level. Programmers work at this level.<\/p>\n 3) View level is the highest level of data abstraction. It is concerned with the way in which the users view the database. It describes only part of the database.<\/p>\n Question 25. a) Identify the primary keys and candidate keys. b) \u03c32Balance>200000<\/sub> (ACCOUNT) Question 26. Question 27. b) Explain about SELECT, INTERSECTION and SET DIFFERENCE operations with example. [Say <\/span>– 2016]<\/span> (3) b) SELECT operation Syntax, eg. \u03c3Salary<100000 <\/sub>(EMPLOYEE)-selects tuple whose salary is less than 10000 from EMPLOYEE relation.<\/p>\n Intersection operation Set difference operation (-) Question 28. 2) Inconsistency can be avoided – If redundancy occurs there is a chance to inconsistency. If redundancy is removed then inconsistency cannot occur.<\/p>\n 3) Data can be shared – The data stored in the database can be shared by the users or programs.<\/p>\n 4) Standards can be enforced – The data in the database follows some standards. Eg: a field ‘Name\u2019 should have 40 characters long. Some standards are ANSI, ISO, etc.<\/p>\n 5) Security restrictions can be applied – The data is of great value so it must be kept secure and private. Data security means the protection of data against accidental or intentional disclosure or unauthorized destruction or modification by unauthorized person.<\/p>\n 6) Integrity can be maintained – It ensures that the data is to be entered in the databse is correct.<\/p>\n 7) Efficient data access – It stored huge amount of data efficiently and can be retrieved whenever a need arise.<\/p>\n 8) Crash recovery – Sometimes all or a portion of the data is lost when a system crashes. A good DBMS helps to recover data after the system crashed.<\/p>\n b)<\/p>\n Question 29. Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. Question 7 (1 Mark) Question 8. Question 9. Question 10. Question 11. Question 12. Question 13. Question 14. Question 15. Question 16. Question 17. Question 18. Question 19. Question 20. Efficient data access -: It stored huge amount of data efficiently and can be retrieved whenever a need arise.<\/p>\n Data can be shared – The data stored in the database can be shared by the users or programs. Standards can be enforced – The data in the database follows some standards. Eg: a field \u2018Name\u2019 should have 40 characters long. Some standards are ANSI, ISO, etc.<\/p>\n Security restrictions can be applied – The data is of great value so it must be kept secure and private. Data security means the protection of data against accidental of intentional disclosure or unauthorized destruction or modification by unauthorized person.<\/p>\n Integrity can be maintained – It ensures that the data is to be entered in the database is correct.<\/p>\n Crash recovery- Some times all ora portion of the data is lost when a system crashes. A good DBMS he’psto recover data after the system crashed.<\/p>\n Question 21. Question 22. Question 23.
\nWhat are the advantages of DBMS? [MARCH – 2008] <\/span>(5)
\nOR
\nConsider there is a strike against the introduction of computer in your firm. How can you convince the ben-efits of computerization to the employees by pointing out the benefits of database over manual system?
\nAnswer:
\n1) Data Redundancy .Duplication of data is known as redundancy, i.e., the same data may be repeated in many files. It leads to higher storage and access cost. So data redundancy should be eliminated.<\/p>\n
\nThe repetition of same data in a file system is known as ……….. . [MARCH – 2009]<\/span>
\nAnswer:
\nData Redundancy<\/p>\n
\nWhat is a Cartesian product? [MARCH – 2009]<\/span>
\nAnswer:
\nCartesian product returns a relation consisting of all possible combinations of the tuple from two relations. Which is a binary operation. It is denoted by X. It is also called Cross Product.<\/p>\n
\nExplain the different levels of data independence. [MARCH – 2009] <\/span>(2)
\nAnswer:
\nData independence is the ability to modify the schema definition in one level without affecting the schema definition at the next higher level. There are two levels Of data independence, Physical data independence and. Logical data independence.<\/p>\n
\nName the different data models available for database systems. Which of them is the most preferred one? Briefly explain with a suitable example. [FEBRUARY – 2009]<\/span> (S)
\nAnswer:
\nThere are three models:-
\na) Hierarchical Model:
\nIt assigns records to different levels of hierarchy. A lower level record is called the child and the higher level is called the parent. Data redundancy is the disadvantage of this model.<\/p>\n
\nExplain two unary operations in RDBMS using an example. [FEBRUARY – 2009] <\/span>(3)
\nAnswer:
\n1) Select: It is used to select tuples in a relation that satisfy a selection condition. To denote selection the lowercase Greek letters are used. The condition appears as a subscript to a. The relation is given in the parenthesis.
\nEg:
\nTo select the tuples whose salary > 5000 from Employee relation Employee)<\/p>\n
\nEg:
\nTo select name and salary from the relation Employee.
\nnna\u2122,salary (Employee)<\/p>\n
\nSelect a terminology which is not a part of DBMS. [JUNE – 2009]<\/span> (1)
\na) Relation b) Function c) Domain d) Tuple
\nAnswer:
\nFunction<\/p>\n
\nExplain the different levels of data abstraction. [JUNE – 2009] <\/span>(3)
\nAnswer:
\n1) Physical Level is the lowest level. It describes how the data is actually stored in the storage medium. At physical level complex low-level data structures are described in detail.<\/p>\n
\nWhat are the components of DBMS? Explain. [JUNE – 2009] <\/span>(3)
\nAnswer:
\na) databases – database is an organized collection of information.
\nb) Data Definition Language(DDL) – Data Definition Language is used to specify the definitions of Da-tabase Schema. The result of compilation of DDL statements is a set of tables stored in a special file called data dictionary.
\nc) Data Manipulation Language(DML) – It is a lan-guage that enable users to access or manipulate data in the database. It also provides interfaces with programming languages.
\nd) Users – users interact with DBMS indirectly via application programs or directly via simple query language.<\/p>\n
\nExplain the structure of a file. [JUNE – 2009] <\/span>(2)
\nAnswer:
\nThe structure of a file
\nField: A field is the smallest unit of data. Ex: roll number, name.<\/p>\n
\n__________ is the smallest unit of data. [JUNE – 2009]<\/span> (1)
\na) Record
\nb) file
\nc) key
\nd) field
\nAnswer:
\nd. Field<\/p>\n
\nConsider the database of Online Ticket reservation. Explain the classification of the users of this database. [MARCH – 2010] <\/span>(3)
\nAnswer:<\/p>\n\n\n
\n A<\/td>\n B<\/td>\n<\/tr>\n \n Database Administrator<\/td>\n b) Person who has a central con\u00adtrol over definition and DBMS.<\/td>\n<\/tr>\n \n Application Programer<\/td>\n c) Computer professionals who in\u00adteract with the DBMS through Application programs<\/td>\n<\/tr>\n \n Users<\/td>\n a) Not concerned with or even aware of details of the DBMS.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nThere is an attribute Roll number in the table STUDENT. This attribute is also the candidate key in the table EXAM. So the Roll number is considered as key in the table EXAM. [MARCH – 2010]<\/span>
\n(a) Foreign
\n(b) Primary
\n(C) Alternate
\n(d) Super
\nAnswer:
\n(a) Foreign<\/p>\n
\nConsider the following table and write relational al-gebra operations for the following: [MARCH – 2010] <\/span>(3)
\nStudent<\/p>\n\n\n
\n Regno<\/td>\n Name<\/td>\n Mark<\/td>\n Mark2<\/td>\n Total<\/td>\n<\/tr>\n \n 101<\/td>\n ABC<\/td>\n 18<\/td>\n 36<\/td>\n 54<\/td>\n<\/tr>\n \n 102<\/td>\n XYZ<\/td>\n 45<\/td>\n 48<\/td>\n 93<\/td>\n<\/tr>\n \n 103<\/td>\n ZYX<\/td>\n 38<\/td>\n 46<\/td>\n 84<\/td>\n<\/tr>\n \n 104<\/td>\n BCD<\/td>\n 45<\/td>\n 46<\/td>\n 91<\/td>\n<\/tr>\n \n 105<\/td>\n DEF<\/td>\n 32<\/td>\n 41<\/td>\n 73<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nb) To display cnly Regno and Name of all students.
\nAnswer:
\na) \u03c3Total>90<\/sub> (Student)
\nb) \u03c0Regno, Name<\/sub>\u00a0(Student)<\/p>\n
\nBriefly explain the different keys that are used in RDBMS. [MARCH – 2010] <\/span>(4)
\nAnswer:<\/p>\n\n
\nMatch the following with the levels of abstraction to which the users are primarily associated: [MARCH -2011] <\/span>(3)
\nLevels of Abstraction – Users
\n1. Physical level – A. Naive users
\n2. Logical level – B. Database administrator
\n3. View level – C. Application programmer
\nAnswer:
\n1) Physical Level – Database Administrator
\n2) Logical Level – Application programmer
\n3) View Level – Naive users<\/p>\n
\nA data model provides a way to represent data and their relationships. [MARCH -2011] <\/span>(3)
\na) Which data model assigns records to diferent levels of hierarchy?
\nb) Briefly explain the relational data model.
\nAnswer:
\na) Hierarchical Data Model
\nb) In relational data model data are stored as tables. Here the term relation means table. A table consists of rows and columns. Columns mean attributes and rows means tuples.<\/p>\n
\nExplain how data is organized for effective storage and retrieval of information. [MARCH -2011] <\/span>(2)
\nAnswer:
\nThere are three data models used for effective storage and retrieval of information. They are hierarchical, network and relational data models.<\/p>\n
\nWhich is not an RDBMS package? [MARCH -2011] <\/span>(1)
\na) Oracle
\nb) SQL Server
\ne) Mysql
\nd) HTML
\nAnswer:
\n(d) HTML<\/p>\n
\nThe smallest unit of stored data in a database is [MARCH -2011] <\/span>(1)
\nAnswer:
\nField<\/p>\n
\nMini created a relation in which two of the tuples have the same combination of values for all their at tributes.
\nIs this allowed? Give reason. [MARCH -2011] <\/span>(2)
\nAnswer 1.
\nNo. It is not allowed because a good DBMS does not allow duplication of the same data. i.e. data redundancy is not allowed.<\/p>\n
\nYes. Same values of data is allowed if primary key or unique key is not defined in the relation.<\/p>\n
\nWhat \u00a1s the importance of primary key? [MARCH -2011]<\/span> (2)
\nAnswer:
\nKey: A pnmary key is one of the Candidate Keys. It is a set of one or more attributes that can uniquely identify tiiples in a relation.<\/p>\n
\nDiscuss the levels of data abstraction in DBMS. [March – 2016] <\/span>(3)
\nAnswer:
\n1) Physical Level is the lowest level.lt describes how ‘ the data is actually stored in the storage medium. At physical level complex low-level data structures are described in detail.<\/p>\n
\nIn the ACCOUNT relation shown below [March – 2016]<\/span><\/p>\n\n\n
\n Acc.Number<\/td>\n \u00a0Name<\/td>\n \u00a0Balance<\/td>\n \u00a0Type<\/td>\n<\/tr>\n \n 1000<\/td>\n \u00a0Simon<\/td>\n \u00a01,50,000<\/td>\n \u00a0SB<\/td>\n<\/tr>\n \n i001<\/td>\n \u00a0Abey<\/td>\n \u00a02,00,000<\/td>\n \u00a0SB<\/td>\n<\/tr>\n \n 1002<\/td>\n \u00a0jambal<\/td>\n \u00a01,00,000<\/td>\n \u00a0SB<\/td>\n<\/tr>\n \n 1003<\/td>\n \u00a0Ram<\/td>\n \u00a02.50,000<\/td>\n \u00a0SB<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nb) Select all account holders with balance greater than Rs. 2,00,000. (2)
\nAnswer:
\na) Primary key-ACC. Number
\nCandidate keys – Name and Balance<\/p>\n
\nOR
\nSelect * from Account where Balance>200000<\/p>\n
\nWhat are the major advantages of the relational model over other data models? [Say – 2016] <\/span>(1)
\nAnswer:
\nThe relational data model has no redundancy and no complexity.<\/p>\n
\na) Classify the following operations in relational algebra into unary and binary operations:
\n(1) UNION
\n(2) SELECT
\n(3) SET DIFFERENCE
\n(4) PROJECT (1)<\/p>\n
\nAnswer:
\na) Unary Binary
\n(2) SELECT
\n(1) UNION
\n(4) PROJECT
\n(3) SET DIFFERENCE<\/p>\n
\nSELECT operation is used to select tuples in a relation that satisfy a selection condition. Greek letter cr (sigma) is used to denote the operation.<\/p>\n
\n\u03c3Condition<\/sub>\u00a0(relation)<\/p>\n
\nThis operation returns a relation consisting of all the tuples appearing in both of the specified rela-tions. It is denoted by n. It can takes place only on compatible relations, e.g. FOOTBALL \u2229 CRICKET returns the players who are in both football and cricket teams.<\/p>\n
\nAll tuples appearing in the first relation and not in the second.<\/p>\n
\na) Discuss the advantages of DBMS. (3)
\nb) Create a database schema for the relation VEHICLE. [MARCH -2017] <\/span>(2)
\nAnswer:
\na) Advantages of DBMS
\n1) Data Redundancy-It means duplication of data. DBMS eliminates redundancy. DBMS does not store more than one copy of the same data.<\/p>\n\n\n
\n RegNo<\/td>\n Owner Name<\/td>\n Make<\/td>\n Year of Mfr<\/td>\n Cub_Capacity<\/td>\n<\/tr>\n \n KL-45-L-100<\/td>\n Achuth<\/td>\n TOYOTO<\/td>\n 2015<\/td>\n 2500<\/td>\n<\/tr>\n \n KL-45-N-1000<\/td>\n RAJU<\/td>\n HONDA<\/td>\n 2016<\/td>\n 1100<\/td>\n<\/tr>\n \n KL-45-P<\/td>\n JOSE<\/td>\n MARUTHI<\/td>\n 2017<\/td>\n 1000<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n_________ in a table gives the complete data of a particular entity. [Say – 2017]<\/span>
\na) Tuple
\nb) Attribute
\nc) Domain
\nd) Schema (1)
\nAnswer:
\nd) Schema<\/p>\nPlus Two Computer Science Chapter Wise Assess Questions and Answers<\/h3>\n
\nWho is responsible for managing and controlling the activities associated with the database? (1 Mark)
\na) Database administrator
\nb) Programmer
\nc) Native user
\nd) End user
\nAnswer:
\na) Database administrator<\/p>\n
\nIn the relational model, cardinality is the _______ . (1 Mark)
\na) numberoftuples
\nb) number of attributes
\nc) number of tables
\nd) number of constraints
\nAnswer:
\na) numberoftuples<\/p>\n
\nCartesian product in relational algebra is _______ . (1 Mark)
\na) a Unary operator
\nb) a Binary operator
\nc) a Ternary operator
\nd) not defined
\nAnswer:
\nb) a Binary operator<\/p>\n
\nAbstraction of the database can be viewed as _________ . (1 Mark)
\na) two levels
\nb) four levels
\nc) three levels
\nd) one level
\nAnswer:
\nc) three level<\/p>\n
\nIn a relational model, relations are termed as __________ . (1 Mark)
\na) tuples
\nb) attributes
\nc) tables
\nd) rows
\nAnswer:
\nc) tables<\/p>\n
\nIn the abstraction of a database system the external level is the ___________ . (1 Mark)
\na) physical level
\nb) logical level
\nc) conceptual level
\nd) view level
\nAnswer:
\nd) view level<\/p>\n
\nRelated fields in a database are grouped to form a ___________ .
\na) data file
\nb) data record
\nc) menu
\nd) bank
\nAnswer:
\nb) data record<\/p>\n
\nA relational database developer refers to a record as ___________ . (1 Mark)
\na) criteria
\nb) relation
\nc) tuple
\nd) attribute
\nAnswer:
\nc) tuple<\/p>\n
\nAn advantage of the database management approach is ___________ . (1 Mark)
\na) data is dependent on programs
\nb) data redundancy increases
\nc) data is integrated and can be accessed by multiple programs
\nd) none of the above
\nAnswer:
\nc) data is integrated and can be accessed by multiple programs<\/p>\n
\nData independence means (1 Mark)
\na) data is defined separately and not included in programs
\nb) programs are not dependent on the physical at-tributes of data
\nc) programs are not dependent on the logical at-tributes of data
\nd) both (b) and (c)
\nAnswer:
\nd) both (b) and (c)<\/p>\n
\nKey to represent relationship between tables is called ___________ . (1 Mark)
\na) primary key
\nb) candidate Key
\nc) foreign Key
\nd) alternate Key
\nAnswer:
\nc) foreign key<\/p>\n
\nWhich of the folowing operations is used if we are interested only in certain columns of a table? ___________ . (1 Mark)
\na) Projection
\nb) Selection
\nc) Union
\nd) Select
\nAnswer:
\na) Projection<\/p>\n
\nWhich of the following operations need the partici-pating relations to be union compatible? ___________ . (1 Mark)
\na) UNION
\nb) INTERSECTION
\nc) SET DIFFERENCE
\nd) All of the above
\nAnswer:
\nd) All of the above<\/p>\n
\nWhich database level is closest to the users? ___________ . (1 Mark)
\na) External
\nb) Internal
\nc) Physical
\nd) Conceptual
\nAnswer:
\na) View level (External)<\/p>\n
\nThe result of the UNION operation between R1 and R2 is a relation that includes ___________ . (1 Mark)
\na) all the tuples of R1
\nb) all the tuples of R2
\nc) all the tuples of R1 andR2
\nd) all the tuples of R1 and R2 which have common columns
\nAnswer:
\n(d) All the tuples of R1 and R2 (eliminating the duplication)<\/p>\n
\nA file manipulation command that extracts some of the records from a file is called ___________ . (1 Mark)
\na) Select
\nb) Project
\nc) Join
\nd) Product
\nAnswer:
\na) select<\/p>\n
\nAn instance of relational schema R (A, B, C) has distinct values of A including NULL values. Which one of the following is true? ___________ . (1 Mark)
\na) A is a candidate key
\nb) A is not a candidate key
\nc) A is a primary key
\nd) Both (a) and (c)
\nAnswer:
\na) A is a candidate key<\/p>\n
\nHow many distinct tuples are there in relation instance with cardinality 22? ___________ . (1 Mark)
\na) 22
\nb) 11
\nc) 1
\nd) none
\nAnswer:
\na) 22<\/p>\n
\nA set of possible data values is called ___________ . (1 Mark)
\na) Attribute
\nb) Degree
\nc) Tuple
\nd) Domain
\nAnswer:
\nd) Domain<\/p>\n
\nWhy should you choose a database system instead of simply storing data in conventional files? (5 Mark)
\nAnswer:
\nAdvantages of DBMS over conventional files Data Redundancy – It means duplication of data. DBMS eliminates redundancy. DBMS does not store more than one copy of the same data. Inconsistency can be avoided – If redundancy occurs there is & chance to inconsistency. If redundancy is removed then inconsistency cannot occur.<\/p>\n
\nExplain the different levels of data abstraction in DBMS? (3 Mark)
\nAnswer:
\nLevels of Database Abstraction –
\n1) Physical Level (Lowest Level) – It describes how the data is actually stored in the storage medium.
\n2) Logical Level (Next Higher Level) – It describes what data are stored in the database.
\n3) View Level (Highest level) – It is closest to the users. It is concerned with the way in which the individual users view the data.<\/p>\n
\nHow are schema layers related to the concepts of logical and physical data independence? (3 Mark)
\nAnswer:
\nData Independence – It is the ability to modify the scheme definition in one level without affecting the scheme definition at the next higher level.
\na) Physical Data independence – If is the ability to modify the physical scheme without causing application programs to be rewritten.
\nb) Logical Data Independence – It is the ability to modify the logical scheme without causing application programs to be rewritten.<\/p>\n
\nConsider the instance of the EMPLOYEE relation shown in the following table. Identify the attributes, degree, cardinality and domain of Name and Emp_code. (3 Mark)<\/p>\n
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