Entity-Relationship Diagrams
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- เผยแพร่เมื่อ 27 พ.ค. 2014
- Puzzled over how to make an entity-relationship diagram? This quick video shows you how.
This lecture is only one of fifty on Seventh Morning's "Fundamentals of Business Analysis" course.
Check it out here... This link discounts the course down to $99, but it's only available for the first 500 subscribers...
www.udemy.com/businessanalysi...
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If only there were more quality videos on TH-cam like this! Well paced, easy to understand and well narrated.
David, thanks for your kind words!
@@NorwalkAberdeen make more tutorial vids please
SOOOOOOOO helpful! You sir just summed up an entire chapter of my textbook in less than 9 minutes.
+John Hurley Awesome. Glad it's helpful!
@@NorwalkAberdeen can you help me
THANK YOU!!!! Finally a video that makes sense and properly explains an entity-relationship diagram! Very well done!
They should just play this in my lectures at university! It would have saved them 2 hours of us all wanting to fall to sleep. Thank you for explaining this in an easier-to-understand and not-so-boring way.
exactly what i needed to hear and see to make things simpler. thanks for everything
Who else came here from the "SQL for Data Sciene" course. Week 1, additional studies.
Meee😊
@@geraldineorieoma7169 That's nice, good luck with the studies 😊
what you guys doing now ! I just started studying
Completely newbie here! Although it looks very complex, analogy is very simple. Everything makes sense right now. Thank you for your time!
I'm late to the party on this, but a great instructional video on TH-cam always deserves praise! Thanks a ton!
so much better and well-explained than my databases professor. thanks for making this video, appreciate it! :)
LOL, yeah, Don has a good nerd laugh. Glad you like it.
The video was very simple, clear and easy to understand. Great Job!!
Crazy how I found this video before following Coursera's recommendation to this video! I will binge watch the rest of this!
Thank you so much! This was exactly what I needed!
Very clear and concise explanation, thank you!!
i finally understand these THANK YOU
amazingly intuitive and simple to follow. Thank you. You are an extraordinary teacher.
Much liked your method in actually identifying the Cardinality. Thanks : )
Thats a very helpful explanation. Thanks so much!
This is soo helpful, hoping you make your videos. Your explanation is just very easy to understand
Kudos on explaining an actual ER diagram instead of those confusing data model lookalikes most people choose (which are less abstract, and a lot of people prefer that, but easily lead to mistakes).
I personally prefer listing attributes separately, beneath the ER diagram, to make it cleaner since ER is mostly about relationships and because attributes aren't really crucial for the ER part.
p.s. I also hated these (on my first year), but on my fourth year when I got a serious db project, I finally understood them and started to love, well... appreciate, them.
+slothc Appreciation is good enough :) Regarding the attributes being listed separately, I wouldn't disagree with you. Especially because in the real world, the list of attributes can be enormous and muck up the visual model. Thanks for the kudos!
OMG, I took ER Diagrams from 2 years at college and I used to hate them so much. However, I started to refresh about them because of SQL and well ah I love them now. Strange how people from different parts of the world can have the same Experience! Thank you buddy for the Great Explanation!
Thank you! It was very informative and easy to understand.
It's amazing how a clear voice spoken in neutral english can make all the difference. Given all unintelligible indian tutorials about this that I had to skip before getting to (and staying with) this one.
Yes i wish there was a filter for dialects
here's some voice conversion software: github.com/andabi/deep-voice-conversion
@Louise cris -- TH-cam won't let me reply to your comment! Grr!
In short, these diagrams are put together long before we start to worry about IDs and keys. We would start to use those concepts when creating a logical (or even physical) data model.
great tutorial man, kudos!
Simple and great explanation. Thanks
This was so useful, I'll never be the first one to say it but going around you-tube looking for technical minded videos can be a nightmare even when the videos really are there with the best of intent.
The explanations were clear and simple,each slide was nicely separated so it never felt as though there was too much going on at any one point the voice over that was giving the explanation of the video was clear, engaged and associable *when I say this, I'm criticizing the countless videos that go on with dry, highly scripted lines that just feel abominable to listen to without breaking your own sanity(
Great! Glad it's helpful!
Thank you sir, This video made me understand what my prof tried to explain.
im having trouble with the n and m what side do i use wich
Many thanks, it helped me alot :)
Sweet video hopefully it will make my pass my database exam :)
Good luck!
Clear and concise. Thank you sir!
Great video. This explains a lot.
I want to thank you a lot for this explanation.
Awesome. I was pretty confused in lecture about the ER Diagram. Great video.
Great! Thanks for the feedback. :)
you saved my day ...brilliant
I dont even know how i made it to this video but i just learned something. Great info
Thank you so much. You have made it so easy to understand.
Life saving :) much thanks
Excellent, thank you!
Wow thanks for the easy explanation !
Very helpful for A level, thank you
I spent one hour to see some one good
But you are fantastic 🤩
Thx a lot it helps me ❤️
Superb video, thank you so much.
Good video, thanks.
what about the unique identifier or primary key of each entity?
Great Video.... So helpful....Thanks.................Seventh Morning LLC
Thank you very much sir, you really helped me on my assignment.
Explained in the simplest way, glad I found your video for ER diagrams.
This is really good, I'm surprise on the low number of videos
easily understood .. thanks sir
Thank you sir very imformative and clearly explained the symbols
Simply amazing!
I know it's an old video, but does anyone know how to show a foreign key in chen notation
Thank you, dear author, you literally saved my life!
Ne za chto!
OK, you have to explain as this sounds like an amazing story.... or did you just use literally incorrectly?
i have followe you explanation but may you please clarify on how to list assumptions and how to write a data documentation for the ER diagram
What about Mandatory and Optional relationships?
Thank you!!
5:37 That Laugh LOOOOOL!! its a great video though, Really helped. Thumbs up
merci beacoup de votre explication claire monsieur.
I got so curious from the comments I had to skip forward to hear the laugh before I could concentrate lol.
Me too lol
Thank you!
Really helpful , thank you
What are primary and foreign keys?
it was very good sir...thanks...
Which geomatric shape is used to represent entity relationship in er diargram ?????
very nice video. thank you for the recomendations from learn sql from data science coursera course
Thank you! I got over the hate significantly after watching this video😇
i have an entity (staff). each of the staff members are managed by zero or one staff members, except Jane Thomas who does not have a manager. The staff members may manage zero or more staff members. Attributes for the staff are (ID, Names, Sex and Age)
Small correction: since each course can have a varying number of lectures i.e. Kn, then under the "Lecture" entity box instead of n it should say Kn, and to the left of the "Lecture" entity box instead of n it should say (n x Kn) - since every user can watch a maximum of all the lectures in the n courses.
Chen style takes u- a lot of diagram space by having attributes in individual ovals, and relationships in diamonds instead of just plain lines.
That is true, and they can give the impression that the relationships are entities rather than just descriptors. Couple things to watch out for.
Good job!
4:55 still confuses me, I mean, can we just use 'm' for both sides? Cause it still means multiple, right?
I'm coming from a Maths background, so bare in mind I'm new to this and could be wrong. However, in Maths it would be convention to label them differently due to them being different sets. You could have a different number of courses and users, but still have multiple of each. Therefore we are clarifying that these numbers can be different, where as if we just had both of them as M, there could be an implication that they are the same number.
if I understand it correctly, in the diagram at 8:00 I thnk there is a typo in the relation "has", a course has multiple lectures (it can participate in multiple "has" reln instance)
but a lecture belongs to 1 course, (a lecture can be seen at most one reln instance in the "has" reln set). so, the connection labels 1 and n are not in the correct places, they should be replaced.
you make me love them , thx bro ^_^
Awesome!
MY 9minits not wasted
Which books should I read to gain this kind of knowledge.
Thank You
thanks brother! Plain english is VERY helpful. BTW anyone ever tell you you sound like topher grace (eric from that 70's show)!
Glad it's helpful! And ha, no, I've never heard that until now :)
Thanks a lot
Anyone else here from the Coursera link?
This is a great video!
that soundtrack at the beginning woke me up
Thank you!!!
Thank you
Thanks !
Thanks :)
How many database tables do you need if you have an ER diagram of: user studies course? Do I only have a user and course table with their attributes, or do I need a 3rd table called study?
+meesie1 hello friend, I'm studying computer science probably just as you and what we do is we have 3 tables for an entity - relationship - entity it is a little expensive in the database however this system is used to know exactly what could be the worst scenario for our database if we use a relational system and how much memory we need to assign to the database
Sorry - missed your question somehow!
Just like Jean said, there is a third table.
In this case, it might be called UserCourseMappings or something similar. And the mapping table just contains a column for the UserId and a column for the CourseId. Together those two columns comprise a composite primary key. I believe that's the most common practice. This third table also could be used if you have attributes of the relationship itself (just make additional columns in the mappings table).
not bad this sums up my first week in 9 minutes
thank you
very helpful
"And we connect them to whatever Entity or Attribute they are an Attribute of"
Uhh.. Did you mean Relationship? I'm taking notes so i wanted to get everything right..
Thanks
Can you please explain the attributes, that belong to relationships?
Hi, it's Don Hussey, the instructor.
We don't use attributes on relationships nearly as often as we do on entities. But they're the same concept -- descriptors or data elements that are attached to the relationship.
One example... Look at the ERD in 7:53. See the "Watches" relationship at the top-left of the diagram? Now imagine an attribute coming out of that called "In One Sitting". And for our purposes we can assume that's a Yes/No attribute that tells whether or not the User watches the Lecture in one sitting.
It's an attribute of the *relationship* because it's not an attribute of the user. Neither is it an attribute of the lecture... It's an attribute of the interaction between the two.
Let me know if this doesn't make sense. They're kind of wacky and seldom used.
Seventh Morning LLC Thank you very much,you really helped me a lot...
Thank you this is really clear!
Why use "n" when it can be represent as "m" ? N and M both mean "more than one" right?
What is the difference between m and n, why is there n in one place and m in the other?
@ 2:50- wasn't that an example of many-to-one? many-to-one isn't listed among the types of cardinality. Can someone please help me understand this part better?
thanks
Oh my LORD, my teacher taught this badly
thanx alot
I have this shit on school, thanks for making things clear. Still very much in period of hating these tho :p
I was from biology, physics, chemistry and math group in my school. I took the Information Technology course in university. No one explained this ER diagram very well and I used to hate it. I agree with this coach. I now understand it better. Thanks for the good video.