Conceptele de baza pentru algebra relationala. De asemenea, puteti gasi un film cu cursul explicat in limba romana, la aceasta adresa: https://www.youtube.com/watch?v=ioIQf9XGBKA
Primul curs de Baze de date, pentru cei care sunt interesati sa aiba si slidurile. Filmuletul cu prezentarea il puteti gasi aici: https://youtu.be/hOgGML7N730
2024 State of Marketing Report – by HubspotMarius Sescu
https://www.hubspot.com/state-of-marketing
· Scaling relationships and proving ROI
· Social media is the place for search, sales, and service
· Authentic influencer partnerships fuel brand growth
· The strongest connections happen via call, click, chat, and camera.
· Time saved with AI leads to more creative work
· Seeking: A single source of truth
· TLDR; Get on social, try AI, and align your systems.
· More human marketing, powered by robots
ChatGPT is a revolutionary addition to the world since its introduction in 2022. A big shift in the sector of information gathering and processing happened because of this chatbot. What is the story of ChatGPT? How is the bot responding to prompts and generating contents? Swipe through these slides prepared by Expeed Software, a web development company regarding the development and technical intricacies of ChatGPT!
Conceptele de baza pentru algebra relationala. De asemenea, puteti gasi un film cu cursul explicat in limba romana, la aceasta adresa: https://www.youtube.com/watch?v=ioIQf9XGBKA
Primul curs de Baze de date, pentru cei care sunt interesati sa aiba si slidurile. Filmuletul cu prezentarea il puteti gasi aici: https://youtu.be/hOgGML7N730
2024 State of Marketing Report – by HubspotMarius Sescu
https://www.hubspot.com/state-of-marketing
· Scaling relationships and proving ROI
· Social media is the place for search, sales, and service
· Authentic influencer partnerships fuel brand growth
· The strongest connections happen via call, click, chat, and camera.
· Time saved with AI leads to more creative work
· Seeking: A single source of truth
· TLDR; Get on social, try AI, and align your systems.
· More human marketing, powered by robots
ChatGPT is a revolutionary addition to the world since its introduction in 2022. A big shift in the sector of information gathering and processing happened because of this chatbot. What is the story of ChatGPT? How is the bot responding to prompts and generating contents? Swipe through these slides prepared by Expeed Software, a web development company regarding the development and technical intricacies of ChatGPT!
Product Design Trends in 2024 | Teenage EngineeringsPixeldarts
The realm of product design is a constantly changing environment where technology and style intersect. Every year introduces fresh challenges and exciting trends that mold the future of this captivating art form. In this piece, we delve into the significant trends set to influence the look and functionality of product design in the year 2024.
How Race, Age and Gender Shape Attitudes Towards Mental HealthThinkNow
Mental health has been in the news quite a bit lately. Dozens of U.S. states are currently suing Meta for contributing to the youth mental health crisis by inserting addictive features into their products, while the U.S. Surgeon General is touring the nation to bring awareness to the growing epidemic of loneliness and isolation. The country has endured periods of low national morale, such as in the 1970s when high inflation and the energy crisis worsened public sentiment following the Vietnam War. The current mood, however, feels different. Gallup recently reported that national mental health is at an all-time low, with few bright spots to lift spirits.
To better understand how Americans are feeling and their attitudes towards mental health in general, ThinkNow conducted a nationally representative quantitative survey of 1,500 respondents and found some interesting differences among ethnic, age and gender groups.
Technology
For example, 52% agree that technology and social media have a negative impact on mental health, but when broken out by race, 61% of Whites felt technology had a negative effect, and only 48% of Hispanics thought it did.
While technology has helped us keep in touch with friends and family in faraway places, it appears to have degraded our ability to connect in person. Staying connected online is a double-edged sword since the same news feed that brings us pictures of the grandkids and fluffy kittens also feeds us news about the wars in Israel and Ukraine, the dysfunction in Washington, the latest mass shooting and the climate crisis.
Hispanics may have a built-in defense against the isolation technology breeds, owing to their large, multigenerational households, strong social support systems, and tendency to use social media to stay connected with relatives abroad.
Age and Gender
When asked how individuals rate their mental health, men rate it higher than women by 11 percentage points, and Baby Boomers rank it highest at 83%, saying it’s good or excellent vs. 57% of Gen Z saying the same.
Gen Z spends the most amount of time on social media, so the notion that social media negatively affects mental health appears to be correlated. Unfortunately, Gen Z is also the generation that’s least comfortable discussing mental health concerns with healthcare professionals. Only 40% of them state they’re comfortable discussing their issues with a professional compared to 60% of Millennials and 65% of Boomers.
Race Affects Attitudes
As seen in previous research conducted by ThinkNow, Asian Americans lag other groups when it comes to awareness of mental health issues. Twenty-four percent of Asian Americans believe that having a mental health issue is a sign of weakness compared to the 16% average for all groups. Asians are also considerably less likely to be aware of mental health services in their communities (42% vs. 55%) and most likely to seek out information on social media (51% vs. 35%).
AI Trends in Creative Operations 2024 by Artwork Flow.pdfmarketingartwork
Creative operations teams expect increased AI use in 2024. Currently, over half of tasks are not AI-enabled, but this is expected to decrease in the coming year. ChatGPT is the most popular AI tool currently. Business leaders are more actively exploring AI benefits than individual contributors. Most respondents do not believe AI will impact workforce size in 2024. However, some inhibitions still exist around AI accuracy and lack of understanding. Creatives primarily want to use AI to save time on mundane tasks and boost productivity.
Organizational culture includes values, norms, systems, symbols, language, assumptions, beliefs, and habits that influence employee behaviors and how people interpret those behaviors. It is important because culture can help or hinder a company's success. Some key aspects of Netflix's culture that help it achieve results include hiring smartly so every position has stars, focusing on attitude over just aptitude, and having a strict policy against peacocks, whiners, and jerks.
PEPSICO Presentation to CAGNY Conference Feb 2024Neil Kimberley
PepsiCo provided a safe harbor statement noting that any forward-looking statements are based on currently available information and are subject to risks and uncertainties. It also provided information on non-GAAP measures and directing readers to its website for disclosure and reconciliation. The document then discussed PepsiCo's business overview, including that it is a global beverage and convenient food company with iconic brands, $91 billion in net revenue in 2023, and nearly $14 billion in core operating profit. It operates through a divisional structure with a focus on local consumers.
Content Methodology: A Best Practices Report (Webinar)contently
This document provides an overview of content methodology best practices. It defines content methodology as establishing objectives, KPIs, and a culture of continuous learning and iteration. An effective methodology focuses on connecting with audiences, creating optimal content, and optimizing processes. It also discusses why a methodology is needed due to the competitive landscape, proliferation of channels, and opportunities for improvement. Components of an effective methodology include defining objectives and KPIs, audience analysis, identifying opportunities, and evaluating resources. The document concludes with recommendations around creating a content plan, testing and optimizing content over 90 days.
How to Prepare For a Successful Job Search for 2024Albert Qian
The document provides guidance on preparing a job search for 2024. It discusses the state of the job market, focusing on growth in AI and healthcare but also continued layoffs. It recommends figuring out what you want to do by researching interests and skills, then conducting informational interviews. The job search should involve building a personal brand on LinkedIn, actively applying to jobs, tailoring resumes and interviews, maintaining job hunting as a habit, and continuing self-improvement. Once hired, the document advises setting new goals and keeping skills and networking active in case of future opportunities.
A report by thenetworkone and Kurio.
The contributing experts and agencies are (in an alphabetical order): Sylwia Rytel, Social Media Supervisor, 180heartbeats + JUNG v MATT (PL), Sharlene Jenner, Vice President - Director of Engagement Strategy, Abelson Taylor (USA), Alex Casanovas, Digital Director, Atrevia (ES), Dora Beilin, Senior Social Strategist, Barrett Hoffher (USA), Min Seo, Campaign Director, Brand New Agency (KR), Deshé M. Gully, Associate Strategist, Day One Agency (USA), Francesca Trevisan, Strategist, Different (IT), Trevor Crossman, CX and Digital Transformation Director; Olivia Hussey, Strategic Planner; Simi Srinarula, Social Media Manager, The Hallway (AUS), James Hebbert, Managing Director, Hylink (CN / UK), Mundy Álvarez, Planning Director; Pedro Rojas, Social Media Manager; Pancho González, CCO, Inbrax (CH), Oana Oprea, Head of Digital Planning, Jam Session Agency (RO), Amy Bottrill, Social Account Director, Launch (UK), Gaby Arriaga, Founder, Leonardo1452 (MX), Shantesh S Row, Creative Director, Liwa (UAE), Rajesh Mehta, Chief Strategy Officer; Dhruv Gaur, Digital Planning Lead; Leonie Mergulhao, Account Supervisor - Social Media & PR, Medulla (IN), Aurelija Plioplytė, Head of Digital & Social, Not Perfect (LI), Daiana Khaidargaliyeva, Account Manager, Osaka Labs (UK / USA), Stefanie Söhnchen, Vice President Digital, PIABO Communications (DE), Elisabeth Winiartati, Managing Consultant, Head of Global Integrated Communications; Lydia Aprina, Account Manager, Integrated Marketing and Communications; Nita Prabowo, Account Manager, Integrated Marketing and Communications; Okhi, Web Developer, PNTR Group (ID), Kei Obusan, Insights Director; Daffi Ranandi, Insights Manager, Radarr (SG), Gautam Reghunath, Co-founder & CEO, Talented (IN), Donagh Humphreys, Head of Social and Digital Innovation, THINKHOUSE (IRE), Sarah Yim, Strategy Director, Zulu Alpha Kilo (CA).
Trends In Paid Search: Navigating The Digital Landscape In 2024Search Engine Journal
The search marketing landscape is evolving rapidly with new technologies, and professionals, like you, rely on innovative paid search strategies to meet changing demands.
It’s important that you’re ready to implement new strategies in 2024.
Check this out and learn the top trends in paid search advertising that are expected to gain traction, so you can drive higher ROI more efficiently in 2024.
You’ll learn:
- The latest trends in AI and automation, and what this means for an evolving paid search ecosystem.
- New developments in privacy and data regulation.
- Emerging ad formats that are expected to make an impact next year.
Watch Sreekant Lanka from iQuanti and Irina Klein from OneMain Financial as they dive into the future of paid search and explore the trends, strategies, and technologies that will shape the search marketing landscape.
If you’re looking to assess your paid search strategy and design an industry-aligned plan for 2024, then this webinar is for you.
5 Public speaking tips from TED - Visualized summarySpeakerHub
From their humble beginnings in 1984, TED has grown into the world’s most powerful amplifier for speakers and thought-leaders to share their ideas. They have over 2,400 filmed talks (not including the 30,000+ TEDx videos) freely available online, and have hosted over 17,500 events around the world.
With over one billion views in a year, it’s no wonder that so many speakers are looking to TED for ideas on how to share their message more effectively.
The article “5 Public-Speaking Tips TED Gives Its Speakers”, by Carmine Gallo for Forbes, gives speakers five practical ways to connect with their audience, and effectively share their ideas on stage.
Whether you are gearing up to get on a TED stage yourself, or just want to master the skills that so many of their speakers possess, these tips and quotes from Chris Anderson, the TED Talks Curator, will encourage you to make the most impactful impression on your audience.
See the full article and more summaries like this on SpeakerHub here: https://speakerhub.com/blog/5-presentation-tips-ted-gives-its-speakers
See the original article on Forbes here:
http://www.forbes.com/forbes/welcome/?toURL=http://www.forbes.com/sites/carminegallo/2016/05/06/5-public-speaking-tips-ted-gives-its-speakers/&refURL=&referrer=#5c07a8221d9b
ChatGPT and the Future of Work - Clark Boyd Clark Boyd
Everyone is in agreement that ChatGPT (and other generative AI tools) will shape the future of work. Yet there is little consensus on exactly how, when, and to what extent this technology will change our world.
Businesses that extract maximum value from ChatGPT will use it as a collaborative tool for everything from brainstorming to technical maintenance.
For individuals, now is the time to pinpoint the skills the future professional will need to thrive in the AI age.
Check out this presentation to understand what ChatGPT is, how it will shape the future of work, and how you can prepare to take advantage.
The document provides career advice for getting into the tech field, including:
- Doing projects and internships in college to build a portfolio.
- Learning about different roles and technologies through industry research.
- Contributing to open source projects to build experience and network.
- Developing a personal brand through a website and social media presence.
- Networking through events, communities, and finding a mentor.
- Practicing interviews through mock interviews and whiteboarding coding questions.
Google's Just Not That Into You: Understanding Core Updates & Search IntentLily Ray
1. Core updates from Google periodically change how its algorithms assess and rank websites and pages. This can impact rankings through shifts in user intent, site quality issues being caught up to, world events influencing queries, and overhauls to search like the E-A-T framework.
2. There are many possible user intents beyond just transactional, navigational and informational. Identifying intent shifts is important during core updates. Sites may need to optimize for new intents through different content types and sections.
3. Responding effectively to core updates requires analyzing "before and after" data to understand changes, identifying new intents or page types, and ensuring content matches appropriate intents across video, images, knowledge graphs and more.
A brief introduction to DataScience with explaining of the concepts, algorithms, machine learning, supervised and unsupervised learning, clustering, statistics, data preprocessing, real-world applications etc.
It's part of a Data Science Corner Campaign where I will be discussing the fundamentals of DataScience, AIML, Statistics etc.
Time Management & Productivity - Best PracticesVit Horky
Here's my presentation on by proven best practices how to manage your work time effectively and how to improve your productivity. It includes practical tips and how to use tools such as Slack, Google Apps, Hubspot, Google Calendar, Gmail and others.
The six step guide to practical project managementMindGenius
The six step guide to practical project management
If you think managing projects is too difficult, think again.
We’ve stripped back project management processes to the
basics – to make it quicker and easier, without sacrificing
the vital ingredients for success.
“If you’re looking for some real-world guidance, then The Six Step Guide to Practical Project Management will help.”
Dr Andrew Makar, Tactical Project Management
Unlocking the Power of ChatGPT and AI in Testing - A Real-World Look, present...Applitools
During this webinar, Anand Bagmar demonstrates how AI tools such as ChatGPT can be applied to various stages of the software development life cycle (SDLC) using an eCommerce application case study. Find the on-demand recording and more info at https://applitools.info/b59
Key takeaways:
• Learn how to use ChatGPT to add AI power to your testing and test automation
• Understand the limitations of the technology and where human expertise is crucial
• Gain insight into different AI-based tools
• Adopt AI-based tools to stay relevant and optimize work for developers and testers
* ChatGPT and OpenAI belong to OpenAI, L.L.C.
Product Design Trends in 2024 | Teenage EngineeringsPixeldarts
The realm of product design is a constantly changing environment where technology and style intersect. Every year introduces fresh challenges and exciting trends that mold the future of this captivating art form. In this piece, we delve into the significant trends set to influence the look and functionality of product design in the year 2024.
How Race, Age and Gender Shape Attitudes Towards Mental HealthThinkNow
Mental health has been in the news quite a bit lately. Dozens of U.S. states are currently suing Meta for contributing to the youth mental health crisis by inserting addictive features into their products, while the U.S. Surgeon General is touring the nation to bring awareness to the growing epidemic of loneliness and isolation. The country has endured periods of low national morale, such as in the 1970s when high inflation and the energy crisis worsened public sentiment following the Vietnam War. The current mood, however, feels different. Gallup recently reported that national mental health is at an all-time low, with few bright spots to lift spirits.
To better understand how Americans are feeling and their attitudes towards mental health in general, ThinkNow conducted a nationally representative quantitative survey of 1,500 respondents and found some interesting differences among ethnic, age and gender groups.
Technology
For example, 52% agree that technology and social media have a negative impact on mental health, but when broken out by race, 61% of Whites felt technology had a negative effect, and only 48% of Hispanics thought it did.
While technology has helped us keep in touch with friends and family in faraway places, it appears to have degraded our ability to connect in person. Staying connected online is a double-edged sword since the same news feed that brings us pictures of the grandkids and fluffy kittens also feeds us news about the wars in Israel and Ukraine, the dysfunction in Washington, the latest mass shooting and the climate crisis.
Hispanics may have a built-in defense against the isolation technology breeds, owing to their large, multigenerational households, strong social support systems, and tendency to use social media to stay connected with relatives abroad.
Age and Gender
When asked how individuals rate their mental health, men rate it higher than women by 11 percentage points, and Baby Boomers rank it highest at 83%, saying it’s good or excellent vs. 57% of Gen Z saying the same.
Gen Z spends the most amount of time on social media, so the notion that social media negatively affects mental health appears to be correlated. Unfortunately, Gen Z is also the generation that’s least comfortable discussing mental health concerns with healthcare professionals. Only 40% of them state they’re comfortable discussing their issues with a professional compared to 60% of Millennials and 65% of Boomers.
Race Affects Attitudes
As seen in previous research conducted by ThinkNow, Asian Americans lag other groups when it comes to awareness of mental health issues. Twenty-four percent of Asian Americans believe that having a mental health issue is a sign of weakness compared to the 16% average for all groups. Asians are also considerably less likely to be aware of mental health services in their communities (42% vs. 55%) and most likely to seek out information on social media (51% vs. 35%).
AI Trends in Creative Operations 2024 by Artwork Flow.pdfmarketingartwork
Creative operations teams expect increased AI use in 2024. Currently, over half of tasks are not AI-enabled, but this is expected to decrease in the coming year. ChatGPT is the most popular AI tool currently. Business leaders are more actively exploring AI benefits than individual contributors. Most respondents do not believe AI will impact workforce size in 2024. However, some inhibitions still exist around AI accuracy and lack of understanding. Creatives primarily want to use AI to save time on mundane tasks and boost productivity.
Organizational culture includes values, norms, systems, symbols, language, assumptions, beliefs, and habits that influence employee behaviors and how people interpret those behaviors. It is important because culture can help or hinder a company's success. Some key aspects of Netflix's culture that help it achieve results include hiring smartly so every position has stars, focusing on attitude over just aptitude, and having a strict policy against peacocks, whiners, and jerks.
PEPSICO Presentation to CAGNY Conference Feb 2024Neil Kimberley
PepsiCo provided a safe harbor statement noting that any forward-looking statements are based on currently available information and are subject to risks and uncertainties. It also provided information on non-GAAP measures and directing readers to its website for disclosure and reconciliation. The document then discussed PepsiCo's business overview, including that it is a global beverage and convenient food company with iconic brands, $91 billion in net revenue in 2023, and nearly $14 billion in core operating profit. It operates through a divisional structure with a focus on local consumers.
Content Methodology: A Best Practices Report (Webinar)contently
This document provides an overview of content methodology best practices. It defines content methodology as establishing objectives, KPIs, and a culture of continuous learning and iteration. An effective methodology focuses on connecting with audiences, creating optimal content, and optimizing processes. It also discusses why a methodology is needed due to the competitive landscape, proliferation of channels, and opportunities for improvement. Components of an effective methodology include defining objectives and KPIs, audience analysis, identifying opportunities, and evaluating resources. The document concludes with recommendations around creating a content plan, testing and optimizing content over 90 days.
How to Prepare For a Successful Job Search for 2024Albert Qian
The document provides guidance on preparing a job search for 2024. It discusses the state of the job market, focusing on growth in AI and healthcare but also continued layoffs. It recommends figuring out what you want to do by researching interests and skills, then conducting informational interviews. The job search should involve building a personal brand on LinkedIn, actively applying to jobs, tailoring resumes and interviews, maintaining job hunting as a habit, and continuing self-improvement. Once hired, the document advises setting new goals and keeping skills and networking active in case of future opportunities.
A report by thenetworkone and Kurio.
The contributing experts and agencies are (in an alphabetical order): Sylwia Rytel, Social Media Supervisor, 180heartbeats + JUNG v MATT (PL), Sharlene Jenner, Vice President - Director of Engagement Strategy, Abelson Taylor (USA), Alex Casanovas, Digital Director, Atrevia (ES), Dora Beilin, Senior Social Strategist, Barrett Hoffher (USA), Min Seo, Campaign Director, Brand New Agency (KR), Deshé M. Gully, Associate Strategist, Day One Agency (USA), Francesca Trevisan, Strategist, Different (IT), Trevor Crossman, CX and Digital Transformation Director; Olivia Hussey, Strategic Planner; Simi Srinarula, Social Media Manager, The Hallway (AUS), James Hebbert, Managing Director, Hylink (CN / UK), Mundy Álvarez, Planning Director; Pedro Rojas, Social Media Manager; Pancho González, CCO, Inbrax (CH), Oana Oprea, Head of Digital Planning, Jam Session Agency (RO), Amy Bottrill, Social Account Director, Launch (UK), Gaby Arriaga, Founder, Leonardo1452 (MX), Shantesh S Row, Creative Director, Liwa (UAE), Rajesh Mehta, Chief Strategy Officer; Dhruv Gaur, Digital Planning Lead; Leonie Mergulhao, Account Supervisor - Social Media & PR, Medulla (IN), Aurelija Plioplytė, Head of Digital & Social, Not Perfect (LI), Daiana Khaidargaliyeva, Account Manager, Osaka Labs (UK / USA), Stefanie Söhnchen, Vice President Digital, PIABO Communications (DE), Elisabeth Winiartati, Managing Consultant, Head of Global Integrated Communications; Lydia Aprina, Account Manager, Integrated Marketing and Communications; Nita Prabowo, Account Manager, Integrated Marketing and Communications; Okhi, Web Developer, PNTR Group (ID), Kei Obusan, Insights Director; Daffi Ranandi, Insights Manager, Radarr (SG), Gautam Reghunath, Co-founder & CEO, Talented (IN), Donagh Humphreys, Head of Social and Digital Innovation, THINKHOUSE (IRE), Sarah Yim, Strategy Director, Zulu Alpha Kilo (CA).
Trends In Paid Search: Navigating The Digital Landscape In 2024Search Engine Journal
The search marketing landscape is evolving rapidly with new technologies, and professionals, like you, rely on innovative paid search strategies to meet changing demands.
It’s important that you’re ready to implement new strategies in 2024.
Check this out and learn the top trends in paid search advertising that are expected to gain traction, so you can drive higher ROI more efficiently in 2024.
You’ll learn:
- The latest trends in AI and automation, and what this means for an evolving paid search ecosystem.
- New developments in privacy and data regulation.
- Emerging ad formats that are expected to make an impact next year.
Watch Sreekant Lanka from iQuanti and Irina Klein from OneMain Financial as they dive into the future of paid search and explore the trends, strategies, and technologies that will shape the search marketing landscape.
If you’re looking to assess your paid search strategy and design an industry-aligned plan for 2024, then this webinar is for you.
5 Public speaking tips from TED - Visualized summarySpeakerHub
From their humble beginnings in 1984, TED has grown into the world’s most powerful amplifier for speakers and thought-leaders to share their ideas. They have over 2,400 filmed talks (not including the 30,000+ TEDx videos) freely available online, and have hosted over 17,500 events around the world.
With over one billion views in a year, it’s no wonder that so many speakers are looking to TED for ideas on how to share their message more effectively.
The article “5 Public-Speaking Tips TED Gives Its Speakers”, by Carmine Gallo for Forbes, gives speakers five practical ways to connect with their audience, and effectively share their ideas on stage.
Whether you are gearing up to get on a TED stage yourself, or just want to master the skills that so many of their speakers possess, these tips and quotes from Chris Anderson, the TED Talks Curator, will encourage you to make the most impactful impression on your audience.
See the full article and more summaries like this on SpeakerHub here: https://speakerhub.com/blog/5-presentation-tips-ted-gives-its-speakers
See the original article on Forbes here:
http://www.forbes.com/forbes/welcome/?toURL=http://www.forbes.com/sites/carminegallo/2016/05/06/5-public-speaking-tips-ted-gives-its-speakers/&refURL=&referrer=#5c07a8221d9b
ChatGPT and the Future of Work - Clark Boyd Clark Boyd
Everyone is in agreement that ChatGPT (and other generative AI tools) will shape the future of work. Yet there is little consensus on exactly how, when, and to what extent this technology will change our world.
Businesses that extract maximum value from ChatGPT will use it as a collaborative tool for everything from brainstorming to technical maintenance.
For individuals, now is the time to pinpoint the skills the future professional will need to thrive in the AI age.
Check out this presentation to understand what ChatGPT is, how it will shape the future of work, and how you can prepare to take advantage.
The document provides career advice for getting into the tech field, including:
- Doing projects and internships in college to build a portfolio.
- Learning about different roles and technologies through industry research.
- Contributing to open source projects to build experience and network.
- Developing a personal brand through a website and social media presence.
- Networking through events, communities, and finding a mentor.
- Practicing interviews through mock interviews and whiteboarding coding questions.
Google's Just Not That Into You: Understanding Core Updates & Search IntentLily Ray
1. Core updates from Google periodically change how its algorithms assess and rank websites and pages. This can impact rankings through shifts in user intent, site quality issues being caught up to, world events influencing queries, and overhauls to search like the E-A-T framework.
2. There are many possible user intents beyond just transactional, navigational and informational. Identifying intent shifts is important during core updates. Sites may need to optimize for new intents through different content types and sections.
3. Responding effectively to core updates requires analyzing "before and after" data to understand changes, identifying new intents or page types, and ensuring content matches appropriate intents across video, images, knowledge graphs and more.
A brief introduction to DataScience with explaining of the concepts, algorithms, machine learning, supervised and unsupervised learning, clustering, statistics, data preprocessing, real-world applications etc.
It's part of a Data Science Corner Campaign where I will be discussing the fundamentals of DataScience, AIML, Statistics etc.
Time Management & Productivity - Best PracticesVit Horky
Here's my presentation on by proven best practices how to manage your work time effectively and how to improve your productivity. It includes practical tips and how to use tools such as Slack, Google Apps, Hubspot, Google Calendar, Gmail and others.
The six step guide to practical project managementMindGenius
The six step guide to practical project management
If you think managing projects is too difficult, think again.
We’ve stripped back project management processes to the
basics – to make it quicker and easier, without sacrificing
the vital ingredients for success.
“If you’re looking for some real-world guidance, then The Six Step Guide to Practical Project Management will help.”
Dr Andrew Makar, Tactical Project Management
Unlocking the Power of ChatGPT and AI in Testing - A Real-World Look, present...Applitools
During this webinar, Anand Bagmar demonstrates how AI tools such as ChatGPT can be applied to various stages of the software development life cycle (SDLC) using an eCommerce application case study. Find the on-demand recording and more info at https://applitools.info/b59
Key takeaways:
• Learn how to use ChatGPT to add AI power to your testing and test automation
• Understand the limitations of the technology and where human expertise is crucial
• Gain insight into different AI-based tools
• Adopt AI-based tools to stay relevant and optimize work for developers and testers
* ChatGPT and OpenAI belong to OpenAI, L.L.C.
1. 1/ 34
Normalizare
Baze de date relat¸ionale
Normalizarea bazelor de date
Nicolae-Cosmin Vˆarlan
November 1, 2018
Nicolae-Cosmin Vˆarlan Baze de date relat¸ionale Normalizarea bazelor de date
2. 2/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Modelul relat¸ional - chei (recapitulare de la primul curs)
Supercheie - un atribut sau o mult¸ime de atribute care
identific˘a unic un tuplu ˆıntr-o relat¸ie
Cheie candidat - o supercheie cu proprietatea c˘a nici o
submult¸ime proprie a sa nu este supercheie
Cheie primar˘a - o cheie candidat selectat˘a pentru a identifica
ˆın mod unic tuplele ˆıntr-o relat¸ie
Cheie alternativ˘a - Chei candidat care nu au fost selectate
pentru a juca rolul de cheie primar˘a
Cheie str˘ain˘a - un atribut sau o submult¸ime de atribute dintr-o
relat¸ie care face referint¸˘a la o cheie candidat a altei relat¸i
Nicolae-Cosmin Vˆarlan Baze de date relat¸ionale Normalizarea bazelor de date
3. 3/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
G˘asirea cheilor candidat utilizˆand dependent¸ele funct¸ionale
Intuitiv: Cheia candidat, este de fapt format˘a dintr-o combinat¸ie
de atribute care pot determina unic linia. Dac˘a pot determina unic
linia (deci oricare dintre valorile celorlalte atribute), atunci putem
considera c˘a avem o dependent¸a funct¸ionala de la X ⊆ U c˘atre
toate atributele din U atunci X este cheie ˆın orice relat¸ie r
construit˘a peste R[U].
Formal: Fie R[U] o schem˘a de relat¸ie si Σ o mult¸ime de
dependent¸e funct¸ionale satisf˘acute de R[U]. X ⊆ U este cheie
candidat d.dac˘a X+ = U ¸si ∀X ⊆ X, X + = U
Un atribut se nume¸ste prim dac˘a face parte dintr-o cheie candidat.
Un atribut este neprim dac˘a nu este parte din nicio cheie candidat.
Nicolae-Cosmin Vˆarlan Baze de date relat¸ionale Normalizarea bazelor de date
4. 4/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
. . . reminder (din cursul 2)
Fie X ⊆ U si RA regulile de inferent¸˘a ale lui Armstrong. Not˘am cu
X+
RA
= {A|Σ RA
X → A}
Regulile de inferent¸˘a ale lui Armstrong:
A1: A1...An→Ai
, i = 1, n
A2: A1,...Am→B1,...Br
A1...Am→Bj
, j = 1, r
A1,...Am→Bj, j=1,r
A1...Am→B1,...Br
A3:
A1,...Am→B1,...Br, B1,...Br→C1,...Cp
A1...Am→C1,...Cp
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Revenim - Exemplul 1:
S˘a consider˘am U = {A, B, C} ¸si Σ = {A → B, B → C}. Vom
construi mult¸imea X+
RA
pentru fiecare dintre atribute:
A+
RA
= {A, B, C} (A din A1, B din A → B,
C din A → B, B → C ¸si folosind A3)
B+
RA
= {B, C} (B din A1, C din B → C)
C+
RA
= {C} (C din A1)
Se observ˘a c˘a A este cheie candidat pentru c˘a de el depind
(funct¸ional) celelalte atribute.
Atribute prime: {A}
Atribute neprime: {B, C}
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
S˘a consider˘am U = {A, B, C} si Σ = {A → B, B → C}. Vom
construi mult¸imea X+
RA
pentru fiecare dintre atribute:
Putem organiza atributele t¸inˆand cont de locul unde apar ele ˆın
cadrul dependent¸elor din Σ:
Stˆanga: Apar numai ˆın partea stang˘a a dependent¸elor din Σ.
Mijloc: Apar ¸si ˆın stˆanga ¸si ˆın dreapta dependent¸elor din Σ.
Dreapta: Apar numai ˆın partea dreapt˘a ˆın dependet¸ele din Σ.
Stˆanga Mijloc Dreapta
A B C
Regul˘a: ˆıntotdeauna atributele din Stˆanga sunt atribute prime, cele
din Dreapta sunt neprime. Cele din Mijloc pot fi ˆın oricare dintre
categorii.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Exemplul 2:
Fie U = {A, B, C, D, E, F} ¸si
Σ = {A → BD, B → C, DE → F}. Care sunt cheile candidat ?
Stˆanga Mijloc Dreapta
A, E B, D C, F
A+
RA
= {A, B, C, D} - nu e cheie (nu cont¸ine F), dar cu sigurant¸˘a
apare ˆın orice cheie.
De fapt, am stabilit c˘a fiecare cheie candidat va cont¸ine toate
atributele din “Stˆanga” - ˆın cazul nostru pe A ¸si pe E:
AE+
RA
= {A, B, C, D, E, F}
AE = cheie multivaluat˘a (este compus˘a din mai multe atribute).
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Exemplul 3:
Fie U = {A, B} ¸si Σ = {A → B, B → A}. Care sunt cheile
candidat ?
Stˆanga Mijloc Dreapta
A, B
A+
RA
= {A, B}
B+
RA
= {A, B}
Ambele sunt chei candidat.
Atribute prime: {A, B}
Atribute neprime: ∅
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9. 9/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Dependent¸e pline
Fie R[U] o schema de relat¸ie peste o mult¸ime de atribute U ¸si Σ o
mult¸ime de dependent¸e funct¸ionale ce au loc ˆın R[U]. O
dependent¸a X → A ∈ Σ+ se nume¸ste plin˘a dac˘a X ⊂ X astfel
ˆıncˆat X → A ∈ Σ+.
Exemplu:
R[A, B, C, D]
Σ = {AB → C, B → D, BC → A}
Toate dependent¸ele din Σ sunt pline (e.g. nu avem ˆın Σ+ nici una
dintre dependent¸ele: A → C, B → C, B → A, C → A).
AB → D nu este plin˘a pentru c˘a B ⊂ AB ¸si avem B → D ∈ Σ+
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Atribut tranzitiv dependent
Fie R[U] o schem˘a de relat¸ie peste o mult¸ime de atribute U ¸si Σ o
mult¸ime de dependent¸e funct¸ionale ce au loc ˆın R[U]. Un atribut
A ∈ U se nume¸ste tranzitiv dependent de X (X ⊂ U, A ∈ X)
dac˘a ∃Y ⊂ U astfel ˆıncˆat:
A ∈ U − Y
X → Y ∈ Σ+
Y → A ∈ Σ+
Y → X ∈ Σ+
Exemplu:
R[A, B, C, D, E]
Σ = {AB → C, AB → D, CD → E}
E este tranzitiv dependent de AB (X = AB, Y = CD).
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Dependent¸e triviale
O dependent¸˘a funct¸ional˘a X → Y este trivial˘a dac˘a ¸si numai dac˘a
Y ⊆ X
O dependent¸˘a multivaluat˘a X Y este trivial˘a dac˘a Y ⊆ X sau
dac˘a Z = ∅ (X ∪ Y = U)
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Normalizarea schemelor bazelor de date
Normalizarea este necesar˘a din dou˘a motive:
Pentru eliminarea redundant¸elor.
Pentru a p˘astra datele ˆıntr-o manier˘a consistent˘a.
Normalizarea trebuie f˘acut˘a ˆınc˘a din faza de proiectare a bazei de
date ¸si din acest motiv este firesc s˘a vorbim despre
NORMALIZAREA SCHEMEI bazei de date ¸si nu despre
normalizarea anumitor relat¸ii.
Exist˘a mai multe forme normale (clasice), fiecare aducˆand ceva ˆın
plus fat¸˘a de forma precedent˘a: 1NF, 2NF, 3NF, BCNF, 4NF.
S˘a vedem ˆın ce constau. . .
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
1NF (1971)
Fie U o mult¸ime de atribute ¸si R[U] o schema de relat¸ie.
Spunem c˘a schema de relat¸ie R[U] este ˆın Forma Normala 1 (1NF)
dac˘a ¸si numai dac˘a domeniile atributelor sunt indivizibile ¸si fiecare
valoare a fiec˘arui atribut este atomic˘a.
Pentru a avea o relat¸ie ˆın 1NF, trebuie efectuate urm˘atoarele
operat¸ii:
Eliminarea grupurilor repetitive din fiecare relat¸ie.
Identificarea tuplelor ce ar putea avea duplicate ˆın coloan˘a
printr-o cheie.
Crearea unei noi scheme de relat¸ie avˆand ca atribute:
identificatorul de la punctul precedent ¸si valoarea repetat˘a ca
atribut atomic.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
1NF
Exemplu:
Avem schema: Studenti[nr matricol, nume, prenume, an] ˆın care
student¸ii ar putea avea cˆate dou˘a prenume:
r :
nr matricol nume prenume an
1 Ionescu Maria Ioana 1
2 Popescu Vasile 1
3 Vasilescu Vali Cristi 2
Pasul 1: Elimin˘am grupul repetitiv:
r :
nr matricol nume an
1 Ionescu 1
2 Popescu 1
3 Vasilescu 2
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Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
1NF
Pasul 2: Identificam cheia:
r :
nr matricol nume an
1 Ionescu 1
2 Popescu 1
3 Vasilescu 2
Pasul 3: Creare relat¸ie ˆın care fiecare valoare apare pe un rˆand nou
¸si e legat˘a de relat¸ia principal˘a prin intermediul cheii:
r :
nr matricol prenume
1 Maria
1 Ioana
2 Vasile
3 Vali
3 Cristi
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
1NF
De¸si ar putea p˘area c˘a am utilizat efectiv relat¸ia care este
construita peste R[U], ˆın fapt nu am facut decˆat s˘a modific˘am
schema de realat¸ie R[U] ¸si s˘a construim o nou˘a schem˘a de relat¸ie
ˆın schema bazei noastre de date denumita R [U].
Pasul 1: de fapt a eliminat atributul “prenume” din mult¸imea U.
Pasul 2: de fapt a identificat o cheie candidat (ce se poate face
direct din schem˘a - vezi cum am gasit o cheie candidat din
dependent¸ele funct¸ionale).
Pasul 3: de fapt a construit o nou˘a schem˘a de relat¸ie R [U]
S-ar putea ca ˆın unele locuri s˘a ˆıntˆalnit¸i ideea c˘a relat¸ia este ˆıntr-o
anumit˘a form˘a normal˘a. Aceasta idee este incorect˘a datorit˘a
faptului c˘a normalizarea se realizeaz˘a ˆınainte de a crea baza de
date, ˆın stadiul de proiectare a acesteia !
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF (1971)
O schema de relat¸ie R[U] care este ˆın 1NF, ˆımpreun˘a cu o mult¸ime
de dependent¸e funct¸ionale Σ este ˆın a doua form˘a normal˘a (2NF)
dac˘a orice atribut neprim din R[U] este dependent plin de orice
cheie a lui R[U].
S˘a relu˘am exemplul de la dependent¸e pline:
R[A, B, C, D]
Σ = {AB → C, B → D, BC → A}
1. Gasit¸i cheile
2. Gasit¸i atributele neprime
3. Atributele neprime sunt dependent¸e plin de cheile g˘asite ?
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF
Sa reluam exemplul de la dependent¸e pline:
R[A, B, C, D]
Σ = {AB → C, B → D, BC → A}
Posibilele chei: AB, BC
Atribute prime: A, B, C
Atribute neprime: D
B → D ∈ Σ+. D nu este dependent plin de AB pentru c˘a, de¸si
avem AB → D ∈ Σ+, avem ¸si B → D ∈ Σ+ rezult˘a c˘a R[U]
ˆımpreun˘a cu Σ nu este ˆın 2NF.
Observat¸ie: dac˘a nu avem chei multivaluate, cu sigurant¸˘a R[U]
este ˆın 2NF (pentru c˘a avem numai dependent¸e pline de la chei -
nu putem g˘asi submult¸imi de atribute atunci cˆand cheia este
format˘a dintr-un singur atribut).
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF
Avˆand o schem˘a de relat¸ie R[U] care nu este ˆın 2NF, putem s˘a o
ducem ˆın 2NF urmˆand urm˘atorii pa¸si:
Pasul 1: Identific˘am cheile candidat.
Pasul 2: G˘asim atributele neprime.
Pasul 3: Pentru fiecare din atributele neprime A identific˘am care
sunt atributele dintr-o cheie de care depinde A.
Pasul 4: Cre˘am o nou˘a relat¸ie R peste acele atribute identificate
la pasul anterior ˆımpreun˘a cu atributul neprim pentru care s-a g˘asit
dependent¸a.
Urmat¸i cei patru pa¸si pentru exemplul anterior care nu era ˆın 2NF.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF
Exemplu: Dac˘a avem schema de relat¸ie
OS[nume, versiune, an, companie]
nume versiune an companie
Windows XP 2001 Microsoft
MacOS Sierra 2017 Apple
Ubuntu Bionic Beaver 2018 Ubuntu
Windows 7 2009 Microsoft
MacOS Mojave 2018 Apple
De obicei, cand ne exprim˘am, spunem c˘a Windows XP este facut
de Microsoft. Avem dependent¸a: nume,versiune → companie. ˆIn
acela¸si timp, ¸stim c˘a Windows este f˘acut numai de Microsoft ¸si
MacOS numai de Apple. Deci avem ¸si nume → companie. Fiecare
versiune este f˘acut˘a ˆıntr-un anumit an. Avem: versiune → an.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF
dependent¸e:
nume,versiune → companie
nume → companie
versiune → an
Cheie: (nume, versiune) (apar ˆın stˆanga dependent¸elor)
Atribute neprime: companie
companie nu este dependent plin pentru c˘a, de¸si avem
nume,versiune → companie, totodat˘a avem ¸si nume → companie.
Vom elimina din schema OS atributul companie ¸si vom ad˘auga o
schem˘a de relat¸ie R [nume, companie].
Vom avea a¸sadar. . .
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
2NF
nume versiune an
Windows XP 2001
MacOS Sierra 2017
Ubuntu Bionic Beaver 2018
Windows 7 2009
MacOS Mojave 2018
¸si
nume companie
Windows Microsoft
MacOS Apple
Ubuntu Ubuntu
Este ˆın 2NF ? Mai avem de verificat dac˘a an este dependent plin
sau nu. . . s˘a vedem cum facet¸i asta voi :D
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
3NF (1971)
Schema de relat¸ie R[U] ˆımpreun˘a cu mult¸imea de dependent¸e
funct¸ionale Σ este ˆın forma a treia normal˘a (3NF) dac˘a este ˆın
2NF ¸si orice atribut neprim din R NU este tranzitiv dependent de
nici o cheie a lui R.
(Adic˘a e ˆın 2NF ¸si orice atribut neprim depinde de chei ¸si nu de un
alt atribut neprim sau grupare de atribute neprime)
Exemplu:
Consider˘am schema de relat¸ie R[A, B, C] ¸si
Σ = {AB → C, C → A}
Chei: AB, BC
Atribute neprime: ∅ - deci este ˆın 2NF ¸si ˆın 3NF.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
3NF - glumit¸a de pe wikipedia. . . .
An approximation of Codd’s definition of 3NF, paralleling the
traditional pledge to give true evidence in a court of law, was given
by Bill Kent: [Every] non-key [attribute] must provide a fact about
the key, the whole key, and nothing but the key. 1
A common variation supplements this definition with the oath: so
help me Codd 2.
1
Kent, William - A Simple Guide to Five Normal Forms in Relational
Database Theory, Communications of the ACM 26 (2), Feb. 1983, pp. 120 −
125.
2
Diehr, George. Database Management (Scott, Foresman, 1989), p. 331.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
3NF
Exemplu de normalizare 3NF
Fie schema: Concursuri[materie, an, castigator, IQ], prin IQ
referindu-ne la IQ-ul cˆastig˘atorului.
Se observ˘a c˘a avem dependent¸ele funct¸ionale:
Σ = {(materie, an) → castigator, castigator → IQ}
Cheie primara: (materie, an) Atribute neprime: IQ
Se observ˘a c˘a (materie, an) → IQ ∈ Σ+, ¸si ˆın acela¸si timp
materie → IQ ∈ Σ+ respectiv an → IQ ∈ Σ+. Deci schema de
relat¸ie se afl˘a ˆın 2NF (atributele neprime fiind dependente plin de
chei).
Vom normaliza schema pentru
Concursuri[materie, an, castigator, IQ] prin construirea a dou˘a
scheme diferite: Concursuri[materie, an, castigator] ¸si
Inteligenta[castigator, IQ].
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
BCNF (Boyce-Codd Normal Form) ≡ 3.5NF (1975)
O schem˘a de relat¸ie R[U] ˆımpreuna cu o mult¸ime de dependent¸e Σ
este ˆın BCNF dac˘a este ˆın 1NF ¸si pentru orice dependent¸a
funct¸ional˘a netrivial˘a X → A ∈ Σ+, X este cheie ˆın R[U].
Observat¸ie: O schem˘a de relat¸ie ce este ˆın BCNF este ˆın 3NF.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Obs: O schem˘a ce este ˆın BCNF este ¸si ˆın 3NF.
Consideram (R, Σ) ˆın BCNF - ˆın 1NF este sigur din definit¸ie.
a) PP (RA) c˘a nu e ˆın 2NF, adic˘a exist˘a un atribut neprim A ¸si o
cheie K ¸si A nu este dep. plin de K. Adic˘a exist˘a X ⊂ K a.i.
X → A ∈ Σ+. Deoarece nu consider˘am dep. triviale avem c˘a
A ∈ K. Atunci X este cheie (pentru c˘a (R, Σ) este ˆın BCNF).
Ceea ce ˆınseamn˘a c˘a K nu este cheie (pentru c˘a trebuia s˘a fie
minimal˘a).
b) Deci (R, Σ) ce este ˆın BCNF trebuie s˘a fie ˆın 2NF. PP (RA) c˘a
nu ar fi ˆın 3NF: adic˘a exist˘a un atribut A tranzitiv dependent de o
cheie X. Adica exist˘a Y a.ˆı. A ∈ X, A ∈ Y ¸si avem c˘a:
X → Y ∈ Σ+,Y → A ∈ Σ+ ¸si Y → X ∈ Σ+. Y nu cont¸ine nicio
cheie pentru c˘a altfel am avea Y → ∀ ∈ Σ+ deci ¸si Y → X ∈ Σ+.
Deoarece Y nu este cheie ¸si totusi am Y → A ∈ Σ+ avem c˘a
(R, Σ) NU este ˆın BCNF - fals. Deci este ¸si 3NF
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Descompunerea de tip join f˘ar˘a pierdere
Consider˘am o schem˘a de relat¸ie R[A1, A2, . . . An]. Spunem despre
o mult¸ime ρ = {R1[A1
i1
1
, A1
i1
2
, . . . A1
i1
k1
], R2[A2
i2
1
, A2
i2
2
, . . . A2
i2
k2
] . . .
Rt[At
it
1
, At
it
2
, . . . At
it
kt
]} c˘a este o descompunere de tip join a lui
R[A1, A2, . . . An] dac˘a:
t
p=1
kp
r=1
Ap
ip
r
= {A1 . . . An}
ρ este o descompunere de tip join f˘ar˘a pierdere dac˘a ∀r peste R ce
satisface mult¸imea de dependent¸e funct¸ionale Σ, avem c˘a
r[A1
i1
1
, A1
i1
2
, . . . A1
i1
k1
] r[A2
i2
1
, A2
i2
2
, . . . A2
i2
k2
] . . . r[At
it
1
, At
it
2
, . . . At
it
kt
]
satisface mult¸imea de dependent¸e funct¸ionale Σ.
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Descompunerea de tip join f˘ar˘a pierdere
Teorem˘a: Dac˘a ρ = {R1, R2} este o descompunere a lui R ¸si Σ o
mult¸ime de dependent¸e funct¸ionale, atunci ρ este o decompunere
de tip join f˘ar˘a pierdere cu privire la Σ dac˘a ¸si numai dac˘a
R1 ∩ R2 → R1 − R2 ∈ Σ+ sau R1 ∩ R2 → R2 − R1 ∈ Σ+
(operat¸iile sunt de fapt pe atributele peste care sunt construite
schemele)
Exemplu: Consider˘am R[A, B, C] ¸si Σ = {A → B}.
ρ1 = {R1[A, B], R2[A, C]} este f˘ar˘a pierdere deoarece:
AB ∩ AC = A, AB − AC = B ¸si A → B ∈ Σ+
ρ2 = {R1[A, B], R2[B, C]} este cu pierdere deoarece:
AB ∩ BC = B, AB − BC = A ¸si B → A ∈ Σ+
AB ∩ BC = B, BC − AB = C ¸si B → C ∈ Σ+
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Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Descompunerea de tip join f˘ar˘a pierdere
Putem calcula Σi pentru Ri[Ui] ¸si continua procesul de
descompunere pˆan˘a cˆand ajungem la scheme de relat¸ie ce sunt ˆın
BCNF. Σi = {X → Y |X, Y ∈ Ui} - adic˘a, pentru Ri[Ui] ce este
un element al descompunerii ρ lu˘am acele dependent¸e din Σ care
sunt peste atributele ce sunt ˆın Ui.
Pentru exemplul precedent:
Consider˘am R[A, B, C] ¸si Σ = {A → B}.
ρ1 = {R1[A, B], R2[A, C]} este f˘ar˘a pierdere deoarece:
AB ∩ AC = A, AB − AC = B si A → B ∈ Σ+
avem c˘a Σ1 = {A → B} ¸si Σ2 = ∅
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31. 31/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Alg. pt. descompunerea ˆın join f˘ar˘a pierdere de tip BCNF
Intrare: (R, Σ)
Ie¸sire: ρ = {(R1, Σ1), . . . (Rt, Σt)} = descompunere f˘ar˘a pierdere
a lui R cu privire la Σ. Unde (Ri, Σi) ˆın BCNF, ∀i ∈ {1..t}
Pas 1: ρ = R = R1; se caculeaz˘a Σ+ ¸si cheile din R.
Pas 2: Cˆat timp exist˘a ˆın ρ un cuplu (Ri, Σi) ce nu e ˆın BCNF:
Pas 2.1: Alege X → A din Σi a.i. A ∈ X ¸si X nu cont¸ine cheie
Pas 2.2: S1 = X ∪ {A}; S2 = Ri − A;
Pas 2.3: ρ = ρ − Ri; ρ = ρ ∪ S1 ∪ S2;
Pas 2.4: Se caculeaz˘a Σ+
S1
, Σ+
S2
¸si cheile pentru S1 ¸si S2.
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Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Exemplu
Schema de relat¸ie:
Absolvent(CNP, aNume, adresa,lCod, lNume, lOras, medie,
prioritate)
Σ ={ CNP → aNume,adresa,medie medie → prioritate
lCod → lNume, lOras}
Se descompune ˆın:
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33. 33/ 34
Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Exemplu
Schema de relat¸ie:
Absolvent(CNP, aNume, adresa,lCod, lNume, lOras, medie,
prioritate)
Σ ={ CNP → aNume,adresa,medie medie → prioritate
lCod → lNume, lOras}
Se descompune ˆın:
ρ = { R1[lCod, lNume, lOras], R2[medie, prioritate],
R3[CNP, aNume, adresa, medie], R4[CNP, lCol]}
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Normalizare
Gasirea cheilor folosind dependetele funct¸ionale
Forme Normale: 1NF, 2NF, 3NF, BCNF, 4NF
Bibliografie
Further Normalization of the Data Base Relational Model. -
Frank Edgar Codd; IBM Research Report RJ909 (August,
1971)
Baze de date relat¸ionale. Dependent¸e - Victor Felea; Univ. Al.
I. Cuza, 1996
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