PRESENTACIÓN ADMINISTRACIÓN BASES DE DATOS
Dani
Created on March 22, 2024
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Empezar
Luis Saurina, Adrian Martí, Luis Aragón, Daniel Samblás
Relational databases
Instance: Is a piece of data that comes from an entity in the database, for example, if you have the element library.
Three elements:
- Entitys: People, objects or concepts
- Attributes: Describe about entitys
- Relations: Used to create links between entities.
Entity Relationship Model
What is a Entity Relationship Model ?Tool that allows for the simplified representation of how people, objects, or concepts relate to each other.
Cardinality in the E-R
Ways to represent:
- Rectangles, to represent the entities.
- Ovals, for attributes.
- Diamonds or connecting lines to represent relationships between entities and attributes.
Model E-R
Model E-R
WHAT IS RELATIONAL MODEL??
A collection of data organized in a format of rows and columns. Each table represents an entity or a type of object in the system. We can difference in two types of keys: Primary key: For example, a customer's ID number would be the primary key in a customers table:For example, a customer's ID number would be the primary key in a customers table.Foreign key: An attribute in one table that references the primary key in another table. It is used to establish relationships between tables.
Example Model relational
SQL (Structured Query Language) is a language used to manage and manipulate relational databases, allowing operations such as querying, inserting, updating, and deleting data.In SQL there are 3 sublanguages:-DML (Data Manipulation Language)-DCL (Data Control Language)-DDL (Data Definition Language) 1st
SQL
DDL (Data Definition Language) is used to define and modify the structure of databases and tables. This is the first language used when creating your database.
DdL
To DELETE some values
To SELECT values from a table (QUERY)
To insert VALUES into the table
This one if for giving permissions of INSERT
This one if for giving permissions of SELECT
dcl & dml
DDL (Data Definition Language) comes firstDDL is used to define the structure of the database, including creating, modifying, and deleting database objects such as tables, indexes, views, and relationships. Examples of DDL statements include CREATE TABLE, ALTER TABLE, and DROP TABLE.
DCL
DML (Data Manipulation Language)Data Manipulation Language (DML) is used to manipulate and modify the data stored in a database. DML commands are used to insert, update, and delete data in a database.
dml
SQL (Structured Query Language) queries are commands used to interact with relational databases. Queries allow you to extract, insert, update or delete data from a database. SQL is the language that allows us to communicate with these databases.Types of SQL QueriesSELECT: Used to query (extract) data.INSERT: Used to insert new data into the database.UPDATE: Used to update existing data.DELETE: Delete data from the database.
SQL QUERY
Extract information of a table
SELECT:
SQL QUERY
INSERT: Used to insert new data into the database.
SQL QUERY
SQL QUERY
UPDATE: Used to update existing data.
DELETE: Delete data from the database.