Relational Database Systems

Attribute, _Table_s, _Tuple_, Relation _Schema_, Degree, Cardinality, Column, Relation instance, are some important components of Relational Model

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Programmers and database administrators work at this level, at this level data can be described as certain types of data records gets stored in data structures, however the internal details such as implementation of data structure is hidden at this level.

• PHYSICAL LEVEL

Relational algebra is a relational model query language used on conceptual procedural.

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Itl is a design or blueprint of a database that can later be implemented as a database.

• ER MODEL

These rules are applied to check whether your database is structurally correct and optimal.

• NORMALIZATION

This relationship cannot be represented in a single _table_.

• ONE-TO-MANY

This is a row of the _table_ and it stores the data details according to the _table_ _schema_.

• _TUPLE_

A Total participation of an entity set represents that each entity in entity set must have at least one relationship in a relationship set.

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The following are the Best Practices for creating a Relational Model, except:

• Cells of the _table_ should hold a single value
• The relational model is easy as _table_s consisting of rows and columns is quite natural and simple to understand.
• Each column should be given a unique name
• Columns must contain data about attributes of the entity

This combines two different results obtained by a query into a single result in the form of a _table_.

• _UNION_

The data stored in database at a particular moment of time is called database _schema_.

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This is the process of optimizing the database structure

• Primary keys
• Normalization
• Relations and attributes
• Relationships

It is a set of one of more columns (attributes) to uniquely identify rows in a _table_.

• SUPER KEY

In non-procedural query language, user instructs the system to perform a series of operations to produce the desired results. Here users tell what data to be retrieved from database and how to retrieve it.

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This is the lowest level of data abstraction. It describes how data is actually stored in database. You can get the complex data structure details at this level.

• PHYSICAL LEVEL

This is the middle level of 3-level data abstraction architecture. It describes what data is stored in database.

• LOGICAL LEVEL

A relational attributes defines the _table_ name and its _schema_.

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This relationship is also useful for storing certain sensitive data in a secure _table_, while the non-sensitive ones in the main _table_.

• ONE-TO-ONE

This DDL command has the behavior of the implementation-defined when there are views or integrity constraints defined that reference the _table_ being dropped.

• _DROP _TABLE_

There must be at least one set of attributes that can identify a _tuple_ in a unique manner.

• Referential Integrity constraints
• None of the above
• Domain constraints
• Key constraints

Integrity rules follow certain relational _table_s to ensure that the data they contain stay accurate and are always accessible

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When one user is accessing data in a database, another user can not be accessing the same data at the same time.

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Databases are logically modelled clusters of information, or data. Any collection of data is a database, regardless of how or _where_ it is stored.

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An entity that cannot be uniquely identified by its own attributes and relies on the relationship with other entity.

• WEAK ENTITY

There should be _insert_ion, deletion and updation possible in terms of a single operand. This facility must be available at all level of relations.

• Rule 5: Powerful and Well-Structured Language
• Rule 7: Quality _Insert_ion, _Update_, Deletion
• Rule 6:View Updation rule
• Rule 4: Dynamic Online Catalog

If low level access is allowed for the relational database, it should not be able to subvert the integrity constraints and bypass security to change the data.

• Rule 12: Nonsubversion Rule
• Rule 10: Integrity Independence
• Rule 9: Logical Data Independence
• Rule 8: Physical Data Independence
• Rule 11: Distribution Independence

The following are the four types of attributes, except:

• Multivalued attribute
• Key attribute
• Decomposed attribute
• Composite attribute

Today, there are many commercial Relational Database Management System (RDBMS), such as Oracle, IBM DB2, and Microsoft SQL Lite Server. There are also many free and open-source RDBMS, such as MySQL, mSQL (mini-SQ ) and the embedded Java DB (Apache Derby).

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It is a collection of data represented in rows and columns.

• _TABLE_

Intersection also adds all duplicates before displaying the result.

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This keyword is used to compare strings, and it offers the feature that patterns containing wildcards can be used

• _LIKE_

An attribute can accept values that are outside of their domains.

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A blank is considered equal to another blank, a zero is equal to another zero, so two null values are considered equal.

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These are used to handle the data in the relational relational data model.

• _TABLE_S

Relational database design satisfies the ACID (atomicity, consistency, integrity, and disparity) properties required from a database design.

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The relational model has provided the basis for:

• This is because duplicate data not only waste storage spaces but also easily lead to inconsistencies.
• Numerous database design methodologies
• The standard database access language called structured query language (SQL)
• Research on the theory of data/relationship/constraint

It is a set of one or more SQL statements that make up a logical unit of work.

• TRANSACTION

In relational model, the data and relationships are represented by collection of inter-related _table_s. Each _table_ is a group of column and rows, _where_ column represents attribute of an entity and rows represents records.

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In the relational model, each _table_ contains at least one column that can be used to uniquely identify each row, called a foreign key.

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It is also know as each row of a _table_.

• RECORD

This model is used to represent real life scenarios as entities

It is the smallest organizational structure of a relational database, and represents the various facets that define the records in the _table_.

• COLUMN

The name of the _Table_:

• EMPLOYEE

It is a set of permitted values for an attribute in _table_.

• DOMAIN

A distinguishing feature of relational databases is that it is possible to get data from more than one _table_ and this is what its called.

• _JOIN_

An attribute that can hold multiple values is known as multivalued attribute. It is represented with this geometric shape in an ER Diagram.

• _DOUBLE OVALS_

This database model is one of the early model, in which data are organized in a tree-_like_ structure, similar to modern-day filesystems.

• HIERARCHICAL MODEL

Few relational databases have no limits on field lengths which can't be exceeded.

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SQL commands are divided into categories, the two main ones being Data Manipulation Language (DML) commands and Data Definition Language (DDL) commands. DDL commands deal with data, either retrieving it or modifying it to keep it up-to-date. DML commands create or change _table_s and other database objects such as views and indexes.

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A relationship is represented by double diamond shape in ER diagram, it shows the relationship among entities. T

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Relational calculus is a conceptual procedural query language used on relational model.

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The relational data model was introduced introduced by C. F. Codd in 1980.

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The following are the Four basic _update_ operations performed on relational database model, except:

• Merge
• _select_
• _delete_
• _Insert_

This statement specifies which columns to include in the _result set_.

• _SELECT_
• _DELETE_
• _INSERT_
• _UPDATE_

It shows the relationship among entity sets.

• ER DIAGRAM

First, the rows in a relational _table_ should all be not distinct. If there are no duplicate rows, there can be problems resolving which of two possible _select_ions is the correct one.

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The advantages of the Object Relational model are the following, except:

• Complicated and difficult to handle at times
• Extensibility
• Complex _Data Type_s
• Inheritance

These operators takes the two sets and returns the values that are in the first set but not the second set.

• SET DIFFERENCE

This relationship is, in fact, implemented as two one-to-many relationships, relationships, with the introduction of the junction _table_.

• MANY-TO-MANY

These operators stores the values in two variables can be compared using following operators and n relation between them can be determined.

• RELATIONAL

This is an attribute that is a combination of other attributes.

• COMPOSITE ATTRIBUTE

Key constraints specify that within each _tuple_, and the value of each attribute must be unique.

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For any system to be qualified as a relational database management system, it should manage its data using its relational capability.

• Rule 1: Information rule
• Rule 0: Foundation rule
• Rule 3: Systematic treatment of Null values
• Rule 2: Guaranteed access rule

A hierarchical model represents the data in a tree-_like_ structure in which there are multiple parents for each record.

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This model is one approach for organizing data that has found wide use in database software since it was first devised in the late 1960s.

• RELATIONAL MODEL

Advantages of Object Oriented Model are the following, except:

• It is easier to extend the design in Object Oriented Model.
• The object oriented model is quite flexible in most cases.
• This model can be quite complicated to create and understand.
• Due to inheritance, the _data type_s can be reused in different objects. This reduces the cost of maintaining the same data in multiple locations.

Database design is more art than science, as you have to make many decisions. Databases are usually customized to suit a particular application. Two customized applications are a_like_, and hence, two databases are a_like_.

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This clause in a _SELECT_ statement provides the criteria for _select_ing values.

• _WHERE_

Relational database design mandates the use of a database server in applications for dealing with data management problems.

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Logical _Schema_ is the design of database at view level.

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A cursor can be thought of as a pointer into a file that contains the rows of the _result set_, and that pointer has the ability to keep track of which row is currently being accessed.

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The main advantages of relational databases are that they enable users to easily categorize and store data that can later be queried and filtered to extract specific information for reports.

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How the data stored in blocks of storage is described at this level.

• PHYSICAL _SCHEMA_

The rows that satisfy the conditions of a query are called this.

• _RESULT SET_

A third aspect of data integrity involves the concept of a null value. A database takes care of situations _where_ data may not be available by using a null value to indicate that a value is missing. It does not equate to a blank or zero.

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Total number of rows present in the _Table_.

• Column
• _Tuple_
• Degree
• Cardinality

Relational Integrity constraints is referred to conditions which must be present for a valid relation. These integrity constraints are derived from the rules in the mini-world that the database represents.

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This is a minimal set of attributes (columns) in a _table_ that uniquely identifies _tuple_s (rows) in that _table_.

• PRIMARY KEY

Database systems are made-up of complex data structures. To ease the user interaction with database, the developers shows internal irrelevant details from users.

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The relational data model is the most famous data model and is used by the majority around he world. This is a simple but efficient data model and has the capability to handle data in the best possible manner.

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Referential integrity constraints is base on the concept of Foreign Keys. A primary key is an important attribute of a relation which should be referred to in other relationships

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A __ of the database represents the same form of data.

• COLUMN

It is for a _table_ is the attribute that can uniquely identify all the _tuple_s.

• KEY

This should be specified when creating columns, that will dictate what kind of entries are allowed in that column.

• _DATA TYPE_

A composite attribute is one whose value is dynamic and derived from another attribute. It is represented by dashed oval in an ER Diagram.

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Referential Integrity Rule states that primary key cannot contain NULL. Otherwise, it cannot uniquely identify the row.

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In terms of DBMS, an attribute is a _table_ or entity of a _table_ in database, so by showing relationship among _table_s and their entity, ER diagram shows the complete logical structure of a database.

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The design of a relational relational database is composed of four stages, _where_ the data are modeled into a set of related _table_s. The stages are the following except:

• Define primary keys
• Define relations/attributes
• Attributes
• Define relationships

A second integrity rule of the traditional relational model is that column values must be repeating groups or arrays

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RDBMSs often implement their own unique _data type_s, which may be directly interchangeable with similar _data type_s in other systems. Some common _data type_s include dates, strings, integers, and Booleans.

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In the late 1960s, this computer scientist working at IBM, devised the relational model of database management. His relational model allowed individual records to be associated with more than one _table_, thereby enabling “many-to-many” relationships between data points in addition to “one-to-many” relationships.

• EDGAR F. CODD

Highest level of data abstraction. This level describes the user interaction with database system.

• VIEW LEVEL

It is the Design of a database.

• _SCHEMA_