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Designing Databases
ELISA MELCARNE
Created on May 16, 2024
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Transcript
Designing Databases
PRESENTATION
introduction
In computer science database, or even just DB indicates a collection of related data which, through a computer, is used to represent a certain portion of the real world. The purpose of a database is to collect a certain set of data to then make it available to anyone who wants to use it, regardless of whether the person requesting the database is a simple user or another computer.
This is an index
Sections like this will help you stay organized
The caracteristic of a DBMS
Data Base Managment System (DBMS)
Conceptual design
SQL (Structures Query Language)
The entity-relationship model
Server-side programming whit PHP
Logical design
Relational operation
The caracteristic of a DBMS
A DBMS is a complex software system that manages large amounts of persistent and shared data, ensuring integrity and security by executing coordinated requests, protecting that request from failure, and implementing an access policy. The data model is a collection of concepts that are used to: 1) describe data 2) must respect a series of associations and constraints. The database describes the logical structure and the instance through a schema. The database stored according to a 3-level organization. DBMS allow several degrees of physical and logical data independence
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Conceptual design
Conceptual design is the process of creating and developing initial ideas and concepts to define the overall direction of a design project. During this phase, creative solutions are explored to address the project's goals and requirements, considering factors such as functionality, aesthetics, feasibility and user experience. The main goal is to establish a clear vision and framework for the project before moving on to the more detailed stages of the design process.
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The entity-relationship model
The relational model is based on the concept of a relation, which extends the idea of a mathematical relation between tuples. Each relation consists of attributes with specific names and associated domains of values, including a null value to represent the absence of a value. To ensure data integrity, various constraints can be applied, such as those on domains, tuples, key fields, and referential integrity. Referential integrity constraints are used to establish key correlations between data in different relations.
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Logical design
Logical design is the intermediate stage between conceptual design and implementation, where abstract concepts are transformed into a more detailed and structured plan. It focuses on defining the logical structure of a system without specifying implementation details, such as data models in computer science or layout plans in architecture. The goal is to provide guidance for the subsequent phases of the design process, ensuring consistency and alignment with the initial objectives.
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DBMS(Data Base Management System)
A DBMS (Database Management System) is software that manages and organizes a large amount of data in a database. It is used to store, retrieve, modify, and administer data efficiently and securely, ensuring data integrity and accessibility for users and applications. Access databases contain tables, queries, forms, reports, pages, and macros.Tables have rows (records) and columns (fields) and are used to create queries, forms, and reports. Queries search for specific information in tables based on criteria, retrieving data for display, printing, deletion, or entry into a new table.
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SQL(structured query languag)
SQL (Structured Query Language) it is a domain-specific language used in programming and managing relational databases. SQL allows users to perform various operations on databases, such as retrieving data, updating records, inserting new data, and deleting data. It provides a standardized way to interact with databases, making it a fundamental tool for data manipulation and management in a wide range of applications and industries.
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Server-side programming with php
PHP is an interpreted server-side language with syntax derived from C. Variables in PHP start with a dollar sign ($) and do not require explicit declaration, as PHP is weakly typed and assigns data types automatically. The output of a PHP page is HTML code. HTTP communication in PHP is managed using the associative arrays $_POST and $_GET. PHP can perform recursive HTTP dialogues using the postback technique, and it maintains these dialogues through cookies, sessions, files, and database connections. For database connectivity, PHP can use the ADODB library for Access or the mysqli object for MySQL.
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RELaTIONAL OPERATION
Relational Algebra (RA) is a database language that uses a set of operators to perform relational operations on one or more relations. The six fundamental operators in RA are selection, projection, intersection, natural join, union, and difference. Additional operators, such as right-join and left-join, are derived from these core operators. Queries in a database can be represented in RA using multiple equivalent expressions, which may vary in efficiency even though they produce the same result.
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