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Define the following terms: Entity, Attribute, Attribute Value, Relationship Instance, Composite Attribute, Multi-valued Attribute, Derived Attribute, Complex Attribute, Key Attribute, Value set(Domain), Recursive Relationships?

Entity – An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity. Attribute – In general, an attribute is a characteristic. In a database management system (DBMS), an attribute refers to a database component, such as a table. It also may refer to a database field. Attributes describe the instances in the row of a database. Attribute Value – Attribute value is the real data of a particular entity for each of its attributes. In other word, associated with each real world entities are certain attributes that describe that entity; value of these attributes for any entity is called attribute value. For example, attribute value of first_name of attribute of student_name can be Gyanendra.  Relationship Instance – Each relationship instance ri in
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Compare the difference between the following:

i) Entities and Attributes – Entity -  An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity. ii) an attribute is a characteristic. In a database management system (DBMS), an attribute refers to a database component, such as a table. It also may refer to a database field. Attributes describe the instances in the row of a database. ii) Composite and Atomic attributes –   Composite attribute − Composite attributes are made of more than one simple attribute. For example, a student's complete name may have first_name and last_name. Simple attribute (Atomic) − Simple attributes are atomic values, which cannot be divided further. For example, a student's phone number is an atomic value of 10 digits. iii) Single valued and Mul

Discuss the difference between the ER model and Relational Model?

E-R Model and Relational Model both are the types of Data Model. Data Model describes a way to design database at physical, logical and view level. The main difference between E-R Model and Relational Model is that E-R Model is entityspecific, and Relational Model is table specific. Let us discuss some differences between E-R Model and Relation model with the help of comparison chart shown below.

Explain the characteristics that make a relation different from a file or table?

 Ordering  of tuples in a relation  r Relation defined as a set of tuples of elements have no order among them. Ordering of values within a tuple and an alternative definition of relation Order of attributes and values is not that important. As long as correspondence between attributes and values maintained. Alternative definition of relation Tuples considered as a set of (<attributes>, <value>) pairs. Each pairs gives the value of the mapping from an attribute A 1 to a value v 1 from dom(A 1 ). Use the first definition of relation Attributes and the values within tuples are ordered. Values and Nulls in tuple Represent the values of attributes that may be unknown or may not apply to a tuple. Meanings for null values Value Unknown Value exists but is not available Attribute does not apply to this tuple (also known as value undefined) Each value in a tuple is atomic. Flat relational model

Define Primary Key, Candidate Key and Super Key?

Super Key Super Key is defined as a set of attributes within a table that uniquely identifies each record within a table. Super Key is a super-set of Candidate key. Example - Suppose we have a table that holds all the managers in a company, and that table is called Managers. The table has columns called ManagerID, Name, Title, and DepartmentID. Every manager has his/her own ManagerID, so that value is always unique in each and every row. This means that if we combine the ManagerID column value for any given row with any other column value, then we will have a unique set of values. So, for the combinations of (ManagerID, Name), (ManagerID, TItle), (ManagerID, DepartmentID), (ManagerID, Name, DepartmentID), etc – there will be no two rows in the table that share the exact same combination of values, because the ManagerID will always be unique and different for each row. This means that pairing the Manager ID with any other column(s) will ensure that the

Define the following in term of relational model?

Domain Domain denoted by D. Every attribute has some pre-defined value scope, known as attribute domain. Domain D is a set of atomic values (indivisible).Data type or format is to be specified for each domain. Ex. Name: set of characters strings that represent names of person. Employee_ages: Possible age of employees must be integer values between 15 to 80. Academic_department_codes: values must be ‘CS’, ’ECON’, ‘PHYS’. Attribute   In a relation table, each column is called by its column name or attribute name . the name of a role played by a domain in that relation Exa- s-name, s-id, s-add etc. Tuple   A single row of a table, which contains a single record for that relation is called a tuple. Relation A Database structured to recognize relation between stored items as information. Relation schema   Relation Schema denoted by R. A relation schema describes the relation name(table name),