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Database concept
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- 1five of the disadvantages of a file processing system1.Data integrity issues
2.Security Issues
3.Difficult in data accessing
4.Data inconsistency
5.Data redundancy - 2What do you understand by a database application.Database application is a software program designed to collect, manage and disseminate
information efficiently. - 3What is Data?Data consist of unprocessed raw facts
- 4what is DatabaseA database is an organized collection of structure information, or data ,
typically stored electronically in a computer system. - 5Database Management System(DBMS)Database Management System is a
software for storing, retrieving and updating users data while considering appropriate
security measures. - 6Information-The processed data is called information. Information is an organized and
processed form of data. It is more meaningful than data and is used for decision making. - 7MetadataIt is a set of data that describes and gives information about the data.
- 8What is DDLData Definition Language is a subset of SQL. It is a language for describing data and its
relationships in a database. The language allows tables to be defined in terms of field
names, data type, data size/length, validation rules, default values, presence check, auto
incrementing requirement, indexing requirement and primary key. - 9What is DMLDML stands for Data Manipulation Language which is used to manipulate data. SELECT is
a command used to retrieve rows from a table. The syntax is SELECT [column name(s)]
from [table name] where [conditions]. - 10Describe the three parts of the Relational Model.1.The set of relations and set of domains that defines that way data can be
represented (data structure).
2.Integrity rules that define the procedure to protect the data (data integrity)
3.The operations that can be performed on data (data manipulation) - 11What is AttributeAn attribute refers to a database component such as a table or database
field. - 12What is a TupleA turple is simply a row contained in a table.
- 13What is Degree of a relationthe number of an entity type that is connected to a relationship is
the degree of that relationship. - 14What is Cardinality of a relationThe cardinality of a relationship is the number of related rows
for each of the two objects in the relationship. - 15What is EntityA single unique object in the real world that is being mastered.
- 16What is strong entityStrong entity set is the entity in which there exists a primary key. For example, an entity
set of cars having attributes such as a car's registration number, car's color, car's name is
a strong entity since no two cars can have the same registration number. So, the attributes
registration number can be considered as the primary key, and hence the entity set is a
strong entity set. - 17What is Weak entityWeak entity is an entity set that does not have a primary key. For example, an entity set of
cars having attributes such as a car's color, a car's name is a weak entity since two cars
can have the same color as well as the same name. So, none of the attributes can be
considered as the primary key and hence the entity set is a weak entity set. - 18What is Associative EntityAn associative entity represents an association between two fundamental entities that has
a potential many-to-many cardinality or that holds some attributes. It can be the birth
place, or it can be more generic, representing commonalities between a number of
concrete associative entities, such as the root parents. - 19What are the 5 types of attributes?1.Single attribute
2.Multi-valued attribute
3.Composite attribute
4.Derived attribute
5.Complex attribute - 20what is single attribute ?The single-value attribute can has only one value for a given entity. For example;
the attribute car_model is a single-valued attribute as one car can has only one
model. - 21what is Multi-valued attributeThe attribute which takes up more than a single value for each entity instance is a multi-valued attribute.
Example: Phone number of a student: Landline and mobile. - 22What is Composite attribute ?It is an attribute that can be split into different components. For example; the address can be
split into house number, street number, city, state, or country. - 23What is Derive attributeAn attribute that can be derived from other attributes is derived attributes. For
example: Total and average marks of a student. - 24What is complex attribute ?complex Attribute is a type of attribute in database. It is formed by nesting composite attributes and multi-valued attributes in arbitrary way.
For e.g;
A person can have many phone numbers,many e-mail addresses,home addresses - 25what you understand by cardinality constraintCardinality constraint defines the maximum number of relationship instances in which an
entity can participate. The different cardinalities are :mandatory one mandatory
many,optional one and optional many - 26Primary keyIt uniquely identifies each table record. For example; studentid
- 27Natural primary keyIt is a set of columns that already exist in the table and uniquely identifies a record
in the table. - 28Candidate keyIt is a set of attributes that uniquely identify tuples in a table. For example; in a table
called student record, an email is a candidate keys, as it help us to uniquely identify
the student record in the table. - 29Surrogate keySurrogate key is an artificial key which aims to uniquely identify record. A surrogate
key in DBMS is usually an integer. For example: shown shift timings of the different
employee in a record EMPLOYEE is an example of surrogate key. - 30Foreign keyA foreign key is a column that creates a relationship between two tables. It acts as a
cross-reference between two tables as it references the primary key of another
table. - 31Composite KeyIt is is a combination of two or more columns that uniquely identify rows in a table.
The combination of columns guarantees uniqueness, though individual uniqueness is
not guaranteed. - 32Explain the concept of integrity in a database.Data integrity refers to the overall accuracy, completeness, and reliability of data. It can be
specified by the lack of variation between two instances or consecutive updates of a
record, indicating that your information is error-free. It also corresponds to the security and
integrity controls and methods of regulatory compliance. - 33Domain integrityDomain integrity refers to the range of acceptable values. It refers to the range of
values that we are going to accept and store in a particular column within a
database. - 34Entity IntegrityEach row for an entity in a table should be uniquely identified. This is done with the
help of primary keys. The entity constraint says that the value of the primary key
should not be NULL. If the value of the primary key is NULL then we can't uniquely
identify the rows if all other fields are the same. - 35Referential integrityReferential Integrity is used to maintain the data consistency between two tables.
- 36Explain the implication for primary keys accepting null values.The primary keys is suppose to uniquely identify records, if two records of a single column
have a NULL value, the column values are not considered equal. In simple words two
NULL values are not considered as equal. This is the reason, Primary Key can’t have
NULL values as they are not compared with any other value. - 37Can a foreign key accept null valuesA foreign key can be null , when a foreign key’s is not known at the time of record
generation then it’s kept null, given that column is created nullable. - 38What is normalization ?Normalization is a database design technique that reduces data redundancy and eliminates undesirable characteristics like Insertion, Update and Deletion Anomalies. Normalization rules divides larger tables into smaller tables and links them using relationships.
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- Fichas sobre Database concept, creado por Begué Ivan el 17/08/2022.
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- Begué Ivan
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