Computer Science Test - 4

The correct answer is Uniquely identify a record

• There is always one primary key in a table for each record which is used to uniquely identify that record.
• KEYS in DBMS is an attribute or set of attributes that help you to identify a row(tuple) in a relation(table). They allow you to find the relation between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table. The Key is also helpful for finding a unique record or row from the table. The database key is also helpful for finding a unique record or row from the table.

• There are mainly seven different types of Keys in DBMS and each key has its different functionality:

  1. Super Key -  A super key is a group of single or multiple keys that identifies rows in a table.
  2. Primary Key -  is a column or group of columns in a table that uniquely identify every row in that table.
  3. Candidate Key -  is a set of attributes that uniquely identify tuples in a table. Candidate Key is a super key with no repeated attributes.
  4. Alternate Key -  is a column or group of columns in a table that uniquely identify every row in that table.
  5. Foreign Key -  is a column that creates a relationship between two tables. The purpose of Foreign keys is to maintain data integrity and allow navigation between two different instances of an entity.
  6. Composite Key - A two or more attributes that allow you to uniquely recognize a specific record. It is possible that each column may not be unique by itself within the database.
  7. Surrogate Key -  An artificial key which aims to uniquely identify each record is called a surrogate key. These kinds of keys are unique because they are created when you don't have any natural primary key.

The correct answer is option 1 i.e Database Management System.

Key Points

• Database Management System:
  • A database management system (DBMS) or database system, in short, is a software that can be used to create, manage and controls access to the data stored in the database. Hence option 1 is correct.
  • It lets users create a database, store, manage, update/modify and retrieve data from that database by users or application programs.
  • Some examples of open source and commercial DBMS include MySQL, Oracle, PostgreSQL, SQL Server, Microsoft Access, MongoDB.

Additional Information​ 

• File system:
  • A file system is a process that manages how and where data on a storage disk, typically a hard disk drive (HDD), is stored, accessed and managed.
  • It is a logical disk component that manages a disk's internal operations as it relates to a computer and is abstract to a human user.
  • A file can be understood as a container to store data in a computer.
  • Contents of a file can be texts, computer program code, comma-separated values (CSV) etc. Likewise, pictures, audios/videos, web pages are also files.
• Network Management System (NMS):
  • It is a system designed for monitoring, maintaining, and optimizing a network.
  • It includes both hardware and software, but most often an NMS refers to the software used to manage a network. It also provides multiple services.
• Operating System:
  • It is an interface between a computer user and computer hardware.
  • An operating system is a software which performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers.

The number of tuples in a relation is known as cardinality

Example:

The number of tuples in the above relation is 4

The cardinality of Employee relation is 4.

The correct answer is Table

Additional Information

• When a table is created in a database, there are different fields. These fields collectively form a particular record. For instance, a record of student information would have the fields as his name, class, registration number, etc.
• Database Management System is built to overcome the drawbacks of typical file processing systems.
• DBMS has reduced the data inconsistencies and difficulty in accessing data.
• It supports concurrent multiple users and ensures the security of data.
• It also solves the integrity problem. Database Management System is built to overcome the drawbacks of typical file processing systems.
• DBMS has reduced the data inconsistencies and difficulty in accessing data.
• It supports concurrent multiple users and ensures the security of data.
• It also solves the integrity problem.

The correct option is 1).

Explanation:-

Keys are used in RDBMS:- 

Primary key:- Every relation has at least one candidate key because at least the combination of all its attributes has a unique property. Such type of candidate key which is chosen as a primary key for the table is known as the primary key. Primary keys are used to identify tables.

Foreign key:- A foreign key is a field or group of fields in a database record that points to a key field or group of fields forming a key of another database record in some table. Usually, a foreign key in one table refers to the primary key of another table.

Unique key:- A unique key is a super key that is, in the relational model of database organization, a set of attributes of a relation variable for which it holds that in all relations assign to that variable.

A database is a set of data stored in a computer, and it is usually structured in a way that makes the data easily accessible.

Therefore,  Relational Database Management System refers to a database that stores data in a structured format, using rows and columns.

Concept

• A database schema represents the logical configuration of all or part of a relational database. It can exist both as a visual representation and as a set of formulas known as integrity constraints that govern a database. 
• A database instance is a set of memory structures that manage database files. A database is a set of physical files on disk created by the CREATE DATABASE statement. The instance manages its associated data and serves the users of the database.
• Data Independence is defined as a property of DBMS that helps you to change the Database schema at one level of a database system without requiring to change the schema at the next higher level. Data independence helps you to keep data separated from all programs that make use of it.
• A data domain is the collection of values that a data element may contain. The rule for determining the domain boundary may be as simple as a data type with an enumerated list of values

Hence Option 2 is correct

• A candidate key is a column, or set of columns, in a table that can uniquely identify any database record without referring to any other data
• Each table may have one or more candidate keys, but only the candidate key is chosen which is unique, and it is called the primary key
• a foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table or the same table

Concept :

• In a relational database, a referential integrity constraint is specified between two tables with the help of a foreign key.
• In the Referential integrity constraints, if a foreign key in Table 1 refers to the primary Key of Table 2, then every value of the Foreign Key in Table 1 must be null or be available in Table 2.
• Hence the correct answer is Option 2

Important Points

The attribute of X is referring to the attribute of Y:

If a row is deleted from X, no violation, since X is a referring relation and hence no violation

But if a row is inserted into X, since X is referring to Y, X may contain value outside the domain of the primary key of Y.

If a row is inserted into Y, no violation, since Y is not referring to any other table and hence no violation

But if a row is deleted from Y, since Y is being referred by X, the referred value may be deleted which leads to the violation.

Hence Insert into Y and Delete from X doesn’t cause violation but insert into X causes violation.

Control of data redundancy is an effect of the database system of managing customer databases.

Key Points

Database Managing system:

• Customer data management (CDM) is the way in which businesses keep track of their customer information and survey their customer base in order to obtain feedback.
• CDM embraces a range of software or cloud computing applications designed to give large organizations rapid and efficient access to customer data. Surveys and data can be centrally located and widely accessible within a company, as opposed to being warehoused in separate departments.
• CDM encompasses the collection, analysis, organizing, reporting, and sharing of customer information throughout an organization. Businesses need a thorough understanding of their customers’ needs if they are to retain and increase their customer base.

Important Points

The features of the database management system are:

• Consistent data
• Creation of unit system of data
• No restriction of data
• Cost-friendly
• Leads to the feedback management system