[Oracle entry series] Chapter 2 _ database Basics

[Oracle entry series] Chapter 2 _ database basics-v512 workshop Editor: Xuan Yu

Oracle	Database Overview		Send me an email
Data Modeling	Basic concepts of databases		V512 Studio
E-R Model	Relational Database basic terms		Chinese Emy of Sciences

Basic concepts of databases
Concept: Database: a warehouse that organizes, stores, and operates data in batches. Data Warehouse is a basic term in the database field. Here it refers to its conventional meaning.
Database Management System (DBMS): A software module used to organize and manage data in database software.
Database Administrator (dBA and Database Administrator): management and maintenance personnel who manipulate the database
Database System: a database-based application system or software system that appears at a lower frequency.
Relational Database: a database established or organized based on a relational model.
Relational Database Management System (RDBMS): it is currently the mainstream form of databases
SQL language: Structured Query Language. Common SQL commands include select, insert, delete, update, create, and drop.
SQL is a database language that uses relational models. It is used to interact with various databases and provides common data management and query functions.
SQL classification: DDL, data definition language, for example, create, alter, drop, and truncate
Data manipulation language (DML): such as insert, update, delete, and merge
Data Control Language (DCL): such as grant and revoke
Other language elements (additional language elements): such as transaction control statements: commit, rollback, savepoint
SQL Description: The SELECT statement is the most frequently used one. DBAs can use DCL for database management, which is rarely used by application developers.

 

 

 

Database Overview
Management: Stage 1: manual management: data is not saved. Data is managed by applications, and data structures should be taken into account in programming.
Data is program-oriented and not shared. Data is not independent and changes with its logical and physical structures
Phase 2: file management phase: poor data sharing. Data is stored as files for a long time
Stage 3: Database Management: facilitates data sharing. Data is application-oriented, not application-oriented
History: First Generation: Non-relational database system: came into existence at the end of the 1960s s, including hierarchical and mesh
Second generation: relational database system (rdbs): came into existence in the 1970s S. Oracle represents rdbs.
Third generation: object-relational database system (ordbs and oodbs): Since the middle of the 1980s S. It is also called an object-oriented database system.
Or store and manipulate data in units of objects. So far, it has not launched mature products
Classification: Net-type Database: uses a net-type data model with the record type as the node. For this complicated and intertwined network, data retrieval is very inconvenient.
Hierarchical Database: uses a hierarchical model to simulate things organized by layers in the real world
Relational Database: uses a two-dimensional table structure to store and manage data, and defines the data dependency between tables and tables. Currently, almost all mainstream databases in the industry are relational databases.
Popular relational databases: Oracle (the industry's first place), ibmdb2, SQL Server, Sybase, Informix (its company has been acquired by IBM), etc.
Relational databases use structured query language (SQL) as a bridge between client programs and database servers

 

 

 

Data Modeling
Concept: to store and process objective things in the real world in the form of data, we need to analyze and abstract them.
This process is called data modeling.
Requirement: It can simulate the real world in a more realistic manner, which is easy to understand and easy to implement by computers.
Element: Data Structure: Describes the static characteristics of a transaction
Data operation: Describes the dynamic characteristics of a transaction.
Integrity constraints: Describe the binding relationship between the inside and between things.
Continued 1: The Real World: The relationships between things and things exist objectively.
Concept world: it is the recognition and abstraction of objective things and their relationships in the real world.
In the concept world, modeling the real world from the perspective of users does not depend on specific computer systems and DBMS.
Machine world: further modeling of things in the conceptual world (links between entities and entities) from a computer perspective, abstracting/transforming it into a "Physical Data Model" related to a computer/DBMS"
Continued 2: Concept data model (CDM, conceptual database model): Mainly used for Conceptual Design of databases
Based on the object-relationship (E-R) model, CDM abstracts objective objects in the real world as entities and relationships.
In the machine world, CDM will be converted to the physical data model (PDM, physical database model) supported by a specific DBMS)
Related Terms: entity: objects that exist objectively and can be differentiated from each other
Entity set: a set of the same class objects. Generally, the entity and entity set are mixed and called entities in general. The concept of entity set is rarely emphasized.
Attribute: describes the characteristics of an object.
Relationship: the correspondence between entity sets (associations between real-world things)

 

 

 

Entity-relational model (E-R model, entity-relationship model)
E-R model: Also known as the E-R method, which was proposed by P. p.s. Chen (Chen surnamed American) in 1976, This method uses E-R diagram to describe the concept model of the real world.
In the E-R model, the real world is composed of all objects called entities and the relationships between these objects. Three elements: entity, relation, and attribute
E-R diagram: entity-relationship digoal, is a practical tool to describe the concept world and build a conceptual model
Three elements of E-R diagram: entity: represented by rectangular frame
Attribute: It is represented by an elliptical shape and connected together with an object.
Link between entities: in a diamond box, and connected with the relevant entities respectively, and the contact type must be indicated on the line
There are three types of relationships between entities: one-to-one (), one-to-many (1: N), and multiple-to-many (M: N)

 

 

 

Relational Database basic terms
Term: Relationship: entire two-dimensional table
Link name: Table Name
Yuanzu: Row data (record)
Attribute: column data (field/component)
Attribute name: column name (field name)
Primary Key: unique attribute group for determining the ancestor (keyword)
Field: attribute value range
Link mode: Link name (attribute list ). For example: Student (student ID, name, gender, phone number)
Constraint: domain Integrity Constraint, also known as column integrity. Constraints on the value of a field or attribute
Entity integrity constraints: Also known as row integrity. Each row in the table must have a unique identifier, which is the primary keyword.
Integrity constraints: Also known as integrity constraints. It refers to the reference between multiple tables, that is, to ensure the consistency between the data in the master table and the data in the slave table.

 

 

 

Oracle [Oracle]
Company: SDL, software development laboratories was founded in 1977 and June.
In 1979, SDL was renamed RSI, relational Software Inc.
In 1983, RSI changed its name to Oracle.
Scott is the first formal employee of Oracle except the two founders.
It is currently the world's largest database software and service provider, and the world's second largest software supplier (the first is Microsoft)
Oracle is currently well-deserved first in the industry, with a share of more than 50% in the domestic industry
Followed by IBM DB2, Sybase, and Microsoft SQL Server. In addition, MySQL is widely used.
Databases: global and cross-platform databases. Oracle complies with industrial standards for data access languages, operating systems, user interfaces, and network communication protocols
Supports multi-user, high-performance transaction processing. Powerful security control and integrity control. Support distributed databases and distributed processing
The latest version is 11 GB and G is the grid. It supports grid computing and centralized database operation.
Currently, Oracle9i and I are integrated. It integrates client, server, and other tools