Original subtitles

‫So the relational model now, we looked at the hierarchical model and we looked at the networking model,

‫the networking model being the expansion of the hierarchical model and how they followed this parent

‫child structure, which to its own right had its efficiencies when retrieving data.

‫Because once you had the parent, you had all the child information right there.

‫But it came with its own set of inefficiencies with the networking model because of the way many to

‫many relationships were formed.

‫Like we said, if you were to delete book one from Andre, you would have to go and look at every other

‫parent and see if they had a reference to book one of Andre would a specific relationship.

‫So there were these intricacies in data management that came to be.

‫So in comes the relational model, if God looked at the landscape of how we were organizing data and

‫realized that most of the models we were following, they were informal, there wasn't any set rules

‫in place for the hierarchical model nor the network model.

‫There was this idea and there were these theoretical papers on the models, but there weren't any hard

‫set rules in place to say, hey, this is how you should do it.

‫This is how you get the most out of it, and this is how we're going to model our system.

‫So he came out with the relational model, which had a formalized set of rules, the first model with

‫the formalized set of rules, to be exact.

‫And if we look at the model here, it doesn't follow that parent child like structure anymore.

‫It shows a completely different route.

‫Instead of relating your data through a parent child relationship, it followed a table structure.

‫Organizing your data in tables also called relations.

‫Now you're using what is a table.

‫Well, think of an Excel sheet.

‫An Excel sheet has columns and rows, and when you use an Excel sheet and you have those columns and

‫rows, you can give the sheet a name that's very closely related to what tables are.

‫Our table has the name author and a table has the name book and the columns, although not like Excel,

‫having the name ABC and they do have specific names.

‫Let's take a closer look at that here.

‫You can see three tables over here.

‫You can see the table for author over here.

‫You can see the table for book.

‫And don't pay attention to the middle just yet.

‫We'll get to that.

‫When we look at author, we can see our columns aren't called ABC and we have authorized first name,

‫last name.

‫So we're specifically saying what is going to go in this column?

‫And over here we can see author 20 is Mobily.

‫Author Twenty one is Andre Nagoya.

‫You may ask yourself, why do we have this authority while we want something to uniquely identify our

‫data?

‫Because first and last name?

‫Well, there may be someone with my first and last name.

‫There may be someone with Andre's first and last name.

‫That's not really unique.

‫So we choose something that can uniquely identify each and every piece of data.

‫And the same for book.

‫The book name isn't really unique.

‫Book one, two and three.

‫There may be someone that has the same book name out there.

‫So we choose a book ID.

‫All right.

‫Now I can see you looking at this and being confused.

‫When we looked at the network model in the hierarchical model, we were storing data in that remember

‫the XML format that we were looking at?

‫We were storing it in a parent child like structure and every parent have all of the information of

‫its child.

‫How does this relate to what we're doing in the relational model?

‫Well, remember, I said we're storing all our data separately now.

‫We don't have this parent child structure anymore.

‫We have a table structure, so now instead of having an author parent, each and every author is an

‫individual piece of data with a unique identifier.

‫And each and every book is an individual piece of data with a unique identifier.

‫Now, you may be thinking, OK, I can see that they're completely separate, but how do we link them

‫together?

‫Well, in the relational model, we have a bunch of concepts that we will get into on how to draw relationships

‫between data.

‫This is one way of doing it will create a third table where we say, OK.

‫Author Mo.

‫Wrote book Two Hundred and author Andre also wrote book Two Hundred, so now we can say, Oh they may

‫have co-authored this.

‫And then author Andre also wrote book Two Hundred and One.

‫So Book Two was written by Andre and Book three was written by MO.

‫So by linking their unique identifiers together in a separate table, we can now say, Hey, this author

‫and this book is related, and by retrieving all the authors for a book, we could potentially now say,

‫Oh, this book has two authors.

‫So there may be a co-author situation.

‫So by storing all our data in a flat way unrelated to parent and child like structure, we can now draw

‫relationships in a much simpler way.

‫You could do this in an Excel sheet in a very simple way.

‫You can input this data in one sheet and put this data in another.

‫She'd give the sheet a name book and then in a third sheet you could start putting ideas together.

‫And that is the exact same concept here.

‫Now I hear you saying, OK, OK, but if I put this in Excel, Excel isn't going to tell me that these

‫are actually related.

‫There's some kind of logic there.

‫Right.

‫And you would be correct, the logic of how the relationships are linked are managed by the database

‫management software now.

‫So now we've looked at three models, right?

‫We've looked at hierarchical network and relational.

‫Each and every one of these models, formal or informal rule sets in place, have specific rules.

‫Right.

‫There is a rule that you have to follow.

‫He authorized needs to be unique.

‫Book ID needs to be unique.

‫Hey, in the hierarchical model, you can't have more than two children linked to a parent in the network

‫model.

‫When you change a book that has two parents, we need to change it in both places.

‫All of these things, all of these rules, all of these things that we've talked about need to be managed

‫and we're not going to manage these.

‫These need to be managed automatically.

‫We don't want to do manual data entry.

‫That would be unfair.

‫So like I said, would file processing systems, there's always software in place.

‫And with the models, we went to a database oriented approach, meaning there is one piece of software

‫that is going to manage the model and that is the database management software.

‫Now, we'll look at the relational model more closely in all of its rules later on.

‫But I really want to zoom in and look at the database management software right now because it is the

‫key player in making sure that when we do implement a system like this, a structure like this, that

‫all of the relationships and all of the management of your data and the safety of your data and where

‫your data is going to be saved, it's going to manage all of that.

‫Let's take a closer look at that piece of software, because it is extremely important to the whole

‫picture.