Database Design 34 - Modality

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30 сен 2024

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Комментарии : 46

@subham3613 3 года назад

explaining a complex thing so simply is a quality of a very good teacher .Thank you Caleb.

@jarrydgunter2394 8 лет назад

you are a legend! your videos about cardinality and modality helped me so much. thank you

@AdeleidaBingham 8 лет назад

Hey, you're a great teacher, keep going. I love these. Just a note: your notation example (one cardholder to null or one card) implies that it is not possible to have a card without a card-owner (which, logically, makes sense - why would a bank have a card produced if not for a specific owner?), so just note that 10 min. or so into the video, your card 69 should have an owner? So, I would suggest using an example where there is an owner without a card (because maybe he prefers to only transact online... or his card has not been issued yet, etc. whatever the business reason for the situation). If I'm wrong, please let me know! But otherwise - great teaching.

@LadE89 7 лет назад

Wrong? Isn't your example at 9:40 with ID the other way around? -I-------0-I- means a cardholder can have 0 or 1 cards. Consequently, a cardholder_ID (PK) is valid although it is not referenced as a FK in the card table. Instead, -I-0-------I- means the card_ID 69 can exist without an owner, yes? Or is it me? :)

@mateusztatusko8770 7 лет назад

Yeah, I believe you are right

@saishashankkonduri612 6 лет назад

Right.........

@Deathend 6 лет назад

No, he is talking about the connection between tables. AKA the Primary and Foreign keys. His example means a card can exist without a FK referencing a card_holder. It also has to do with Parent and Child. A card_holder is never going to be a child of a card, but a card will be the child of a card_holder. So the only logical way is card_holder (parent)-> card (child). Also, remember these are each their own respective tables. The card table is already going to exist and have a connection to the card_holder table regardless of whether it has a few NULL values instead of FKs. Now if the card table was the Parent, and the card_holder was the child, you would be correct. In that case it would be saying the FK present in card_holders can be NULL. This parent and child relationship is why he makes the tables the way he does. He almost always has the parent on the left and the child on the right.

@wiguallen1922 8 лет назад

thank you caleb! u really helped me with your videos! thumbs up!. i hope you make web development videos

@dansmar_2414 2 года назад

Old, but Gold. Thank you so much for sharing free valuable contents with us. Your playlist is awesome.

@rad_dad 4 года назад

I've struggled with Modality and this has helped me out immensely. Thanks!

@NotAHomelessGamer 7 месяцев назад

I laughed @ 9:56 when you did a double take on doing 69 as an example. Nice.

@jcjcortz8526 4 месяца назад

Very comprehensive. Thankies fella

@saadsadiq8938 6 лет назад

Its more easier to understand if we say 0 as O (Optional)

@dilancando8948 3 года назад

quienes vienen y que hablan español sjsjsjsjsjsjs

@mirandoo300 3 года назад

why did you say "piss" at the end

@thender5624 3 года назад

Caleb you are left hander.

@emrekalayci 9 лет назад

Good lesson! Thanks :)

@robertkopec7566 Год назад

Hello everyone! First of all, thank you for these tutorials, Całeb. They are really helpful plus it's fun to watch you :) However, I don't get one thing. In your example of cardholder-I----O-

@headphonesandguitar 7 лет назад

you are awesome, this really helped :)

@VuongNgo_pd 10 лет назад

Im wondering how many lessons left :D

@bengkiam 8 лет назад

Hi @CalebTheVideoMaker2, my question is, if modality 0.1 or 0.N then how could be a child table exist without any parent table? Although a parent table might exist without any child table.

@tdawg6795 2 года назад

Very good explanation! I have a suggestion for your videos, perhaps you can make multiple videos of the same topic even though you feel like you have covered them completely in one video. This is because 1) oftentimes a good video is hard to find and 2) I often need to watch more videos on the same topic