ER Model MCQ Quiz in தமிழ் - Objective Question with Answer for ER Model - இலவச PDF ஐப் பதிவிறக்கவும்

Entity integrity constraint:

It states that primary key value cannot be NULL. This is because the primary key value is used to identify individual rows in relation and if the primary key has a NULL value, then we cannot identify those rows.

Cardinality ratio:

It is a concept that describes binary relationship set and its types. It is about the maximum number of entities of one entity set that are associated with the maximum number of entities of other entity set.

Foreign key constraint:

A foreign key joins a table to another table by referencing its primary key. A foreign key constraint specifies that the key can only contain values that are in the referenced primary key and ensures the referential integrity of data that is joined on the two keys.

Participation constraint:

The correct answer is Records, fields

• Each row in a database table represents one instance of the type of object described in that table. A row is also called a record.
• The columns in a table are the set of facts that we keep track of about that type of object. A column is also called a field.

Answer: Option 2

Explanation: 

An entity–relationship model (ER model) describes inter-related things of interest in a specific domain of knowledge. An ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between instances of those entity types. In software engineering, an ER model is commonly formed to represent things that a business needs to remember in order to perform business processes. Consequently, the ER model becomes an abstract data model that defines a data or information structure that can be implemented in a database, typically a relational database.

The correct answer is database

Key Points

• A database is an organized collection of data. It is the collection of schemas, tables, queries, reports, views, and other objects. The data are typically organized to model aspects of reality in a way that supports processes requiring information, such as modelling the availability of rooms in hotels in a way that supports finding a hotel with vacancies.

Important Points

• The various reasons a database is important are −
  • Manages large amounts of data: A database stores and manages a large amount of data on a daily basis. This would not be possible using any other tool such as a spreadsheet as they would simply not work.
  • Accurate: A database is pretty accurate as it has all sorts of built-in constraints, checks, etc. This means that the information available in a database is guaranteed to be correct in most cases.
  • Easy to update data: In a database, it is easy to update data using various Data Manipulation languages (DML) available. One of these languages is SQL.
  • Security of data: Databases have various methods to ensure the security of data. There are user logins required before accessing a database and various access specifiers. These allow only authorized users to access the database.
  • Data integrity: This is ensured in databases by using various constraints for data. Data integrity in databases makes sure that the data is accurate and consistent in a database.
  • Easy to research data: It is very easy to access and research data in a database. This is done using Data Query Languages (DQL) which allow searching of any data in the database and performing computations on it. 

The correct option is (3)

Referenced relation

Concept:-

The referenced relation is the one in which the primary key of one relation is used as a normal attribute in another relation.

Key Points

• The relation which is referencing another relation is called referencing relation and the relation to which other relations refer is called referenced relation.
• We can't delete or update a row from referenced relation if the value of a referenced attribute is used in the value of referencing attribute.
• Any set of attributes that allows us to identify unique rows (tuples) in a given relationship is known as super keys.
• Out of these super keys, we can always choose a proper subset that can be used as a primary key.
• If there is a combination of two or more attributes that are being used as the primary key then we call it a composite key.

The correct answer is Key

Explanation:

• 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 - Only one primary can be possible for a relation, the candidates which are not selected as primary keys for the relation are known as alternate keys.
  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. Compound Key -  has 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. Composite Key -  It is a set of columns that are naturally existed in the relation, and can be combined and used as the primary key for a relation.
  8. Surrogate Key -  An artificial key that aims to uniquely identify each record is called a surrogate key. A column is generated with a combination of sets of the columns and used as the primary key.

The correct answer is Records, fields.

Key Points

• In the Relational database model, a table is a collection of data elements organized in terms of rows and columns. A table is also considered a convenient representation of relations. But a table can have a duplicate row of data while a true relation cannot have duplicate data.
• Fields and records are two basic components of a database, which is an organized collection of information, or data. The term "fields" refers to columns or vertical categories of data; the term "records" refers to rows or horizontal groupings of unique field data. Examples of both database components are seen in older, printed databases and also in modern, computer-based databases.
• A single entry in a table is called a Tuple or Record or Row. A tuple in a table represents a set of related data.
• A table consists of several records(row), each record can be broken down into several smaller parts of data known as Attributes.

The correct answer is option 1.

Concept:

An entity-relationship model (ER model) uses a diagram called an Entity Relationship Diagram to illustrate the structure of a database (ER Diagram). ER diagram has three main components:

• Entity.
• Attribute.
• Relationship.

Entity:

An entity is a type of data item or component. In an ER diagram, an entity is represented by a rectangle.

Attribute:

An attribute describes the property of an entity. An attribute is represented as Oval OR ellipse in an ER diagram.

Relationship:

The relationship is nothing but an association among two or more entities. The Diamonds symbol represents relationship.

Lines:

The link attributes to Entity Sets and Entity sets to Relationship Set.

Hence the correct answer is Ellipse.

Additional Information

Dashed Ellipse is used to denote the derived attribute

Below are the Symbols with their description used in ER Model.

The relation is M : 1

Diagram