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What is relationship in er diagram?
In Database Analysis and Design; the relationship in an ERD can only be mandatory or optional between two entities. Mandatory is where both entities must be present, whereas with optional, you don't always need two entities.
What is the difference between schema and database?
Database schema are the logical structure of entities (tables or object classes) and their relationships (keys, or object associations) in a database. Schema can exist at different levels of abstraction (see: en.wikipedia.org/wiki/Database_schema). Schema themselves may or may not exist as such in a database. In general schema at the higher levels of abstraction are design models that are captured in printed documents, and authored by business analysts and database designers, rather than created by database programmers and stored in the database itself. But in some types of databases, schema at any level of abstaction can be realized physically. In Oracle databases, schema can be realized as schema objects, which are a part of an Oracle database. These schema objects may represent a human user's conceptual model of the knowledge captured in an enterprise database. Thus defined, there can be many schema that can be associated with one physical database. In other kinds of relational database, an abstract user's schema can be represented by logically linked metadata, views, and stored procedures assocated with a user class. In object-oriented databases, especially those based on the highly self-referential language Smalltalk (e.g. Gemstone/S), schema are realized as "physical" objects in the database as a matter of course, as well as in the logical models captured in design documents. The schema objects in such databases are, in essence, the classes comprising the infrastructure of the database or application. Oracle-style user schema are readily created; these would be realized as user interface orchestrator classes.
Difference between an entity class and an entity instance?
"An entity is a person, place, event, or thing about which data is collected...An instance is an occurence of an entity." - Systems Analysis & Design (4th) - DennisAn example of this would be STUDENT as the entity while JACK SMITH is an instance of that entity.If an entity is an individual "person, place, event, or thing about which data is collected", then an entity is an instance. Linguistically, entity is just another word for a single thing ("The existence of a thing as contrasted with its attributes.", Merriam-Webster's On-line Dictionary). Entities that have the same attributes are grouped in what are best called entity classes (it doesn't make sense to refer to a collection of entities as an entity). Entity and entity class are data modeling terms. The corresponding object modeling terms are object and class, albeit that a class typically has operations, which are foreign to an entity class.
What is difference between Cartesian product and natural Join Operation?
Difference Between CARTESIAN PRODUCT & NATURAL JOINT Cartesian product is like the cross product ie every element of one row of one table/entity is multiplied to every column of another table for solving linked queries of two tables ... Where as natural Join is simply joining two or more entities eliminating the common attributes or columns.. @nayan answered it :)
What is intercompany matrix?
It is a matrix indicating the out of balance transaction figures between two entities who are subsidiaries of one another or subsidiaries of some other entity. The matrix is periodicaly reveiwed to diagnose and clear the out of balance figures. The out of balance figures can also be due to foreign exchange transactions between two entities whereby gain/loss arise on revaluation of balances periodically.
Attributes in relational database?
In a relational database, attributes are the characteristics or properties that describe entities in a table. Attributes are represented by columns in a table and hold specific pieces of data related to the entities. Each attribute has a data type that defines the kind of data it can store (e.g., integer, string, date).
Differentiate between the E-R model and Relational model?
The E-R model (Entity-Relationship model) is a visual representation of entities, attributes, and relationships in a database, while the relational model organizes data into tables with rows and columns. The E-R model focuses on the logical design of a database, while the relational model focuses on the physical implementation of data storage and retrieval. E-R model uses entities, attributes, and relationships to depict data structures, while the relational model uses tables, keys, and relationships to organize data.
Theoritical Conceptual and Physical aspects of relational database?
Theoretical aspect: Relational database follows the relational model, which organizes data into tables with rows and columns based on primary and foreign keys. Conceptual aspect: It involves designing the database structure, including defining entities, attributes, and relationships between them. Physical aspect: This refers to the actual implementation of the database design on a physical storage medium, such as hard disks, memory, and indexing structures.
What is relational schema?
A relational schema is a structure that represents the logical view or design of a database. It defines how the data is organized and the relationships between different entities or tables. It typically includes the names of the tables, their attributes or columns, and the constraints that define the relationships between them.
What are the different types of information represented in the ER diagram and the symbols used to represent them?
The different types of information represented in an ER diagram are entities (represented by rectangles), attributes (represented by ovals connected to entities), and relationships between entities (represented by diamonds). Entities are the objects or concepts about which data is stored, attributes are the properties of entities, and relationships define how entities are connected to each other.
Which one of the following diagrams is the most helpful in designing a relational database in which to store object data?
The Entity-Relationship diagram is the most helpful in designing a relational database to store object data. It visually represents entities, their attributes, and the relationships between them, providing a clear understanding of the database structure and enabling effective planning of tables and relationships.
What is the relationship between entities and attributes?
Entities and attributes unable you to explicitly define what information, or data, is beingstored in the database. Relationships are the other powerful feature of relational modelingand give the modeling technique its name. A relationship is a logical linkage between twoentities that describes how those entities are associated with each other. Think ofrelationships as the logical links in a database that turn simple data into useful information.For instance, our definition of a teacher reads: “A person employed by the college who isresponsible for instructing students in a class.”
What are the basic components of a database?
Tables, Entities, Attributes, Primary Keys, and Foreign Keys
What are attributes and entities in database system management?
Entities are the things you're keeping track of. In an video rental database, you keep track of customers, invoices, titles, copies, etc. These are represented in tables where the rows are individual instances of a customer or title. The columns are the attributes, the things that tell us about the instance in the row. The customer's name, address, city, balance, etc. are attributes that help identify the customer. An invoice's attributes might be price, number, date, paid/unpaid, etc. Databases link entities/tables so that a customer, described by his attributes, can be associated with his invoices, describe by his attributes and selected by the invoices 'unpaid' column. "Here's your bills for the last month, Mr. Smith."
What is difference between object and entity?
A database object is represented as one of the following: database, schema, table, column, primary key, and foreign key A database Entity is: An entity is a thing or object of importance about which data must be captured. All things aren't entities - only those about which information should be captured. Information about an entity is captured in the form of attributes and/or relationships. If something is a candidate for being an entity and it has no attributes or relationships, it isn't an entity. Database entities appear in a data model as a box with a title. The title is the name of the entity.
What is the class hierarchy in dbms?
In a relational database management system (RDBMS), the class hierarchy typically includes the following levels: database server, databases, tables (or relations), columns (or attributes), and rows (or tuples). The database server manages connections, access control, and query processing. Databases contain tables, which store data arranged in rows and columns. Columns define the attributes, while rows represent individual records.
What is E-R model. What is an Entity set?
The E-R model is a data model used to describe the relationships between entities in a database. An Entity set is a collection of similar entities (objects) with shared attributes that are grouped together in the database.
