Hey everyone, welcome back to part six of topic four in our database class. In this video, I'm going to introduce conceptual froze foot relationship symbols that we can use in our entity relationship models. Now I'm sure as you're all aware, Rho is a type of bird and the reason that we call these symbols froze foot symbols is that this symbol here, which is our symbol for the conceptual notion of many, is kind of look like the foot of a bird. And so you can imagine that maybe we have like a, I was hard to draw with a mouse, but maybe we have a little bird here and here's our little bird. All right, that's all right, I won't be able to draw this very effectively with my mouse, but just for illustrative purposes, and a little, I don't know, maybe we got a little birdie out here. Drawing a bird. And happy. All right, so this is my attempt at drawing a crow, maybe it has some big feathers. And I'll I, all right, so I don't laugh. The idea here is that this looks like that. And this is where the name crow's foot symbols comes from. We're going to use these symbols to represent some concepts and the first broad care of concepts that we need to consider is just this notion of one versus many. Okay, so in this case, if we're doing these conceptual relationships, we would use these sorts of lines to interconnect tables. And that's something that looks like this would represent one something that looks like that would represent many. So the idea is that we're going to have some tables or some entities. I'll draw them like this. And then we'll have some sort of relationship line that interconnects them. And what we're going to do then is use these various symbols. And then we'll indicate the nature of the relationship on both sides of that line. So if I were to conceptually draw something like what we see here, this would be a one to one conceptual relationship. So earlier we saw an example of was that an employee in a parking space. Imagine that that's a conceptual one to one relationship. Here's an employee. Here's a parking space. So in our world. We reserve parking spaces for individual employees. And if we have this described as a one to one relationship, which is as it is depicted here, what this means. Then is if we were to read this relationship, we would read it as follows when reading the relationship in this direction. We would say each employee is assigned to one parking space because the end of the line here indicates concept of one as we see over here. And if we were to read this relationship in the opposite direction, that is in the direction from parking space to employee, we would say something like each parking space is assigned to one employee. Because this line ending here again is matches what we see conceptually for the notion of one. So this is a one to one relationship because it's one in both directions, right, each end of the line here and here is indicating a notion of one. If we had a different sort of scenario where let's say, for example, that instead of an employee and a parking space sort of relationship, we instead. Had a relationship where it was, I don't know, maybe between employees and let's say projects. So let's imagine a world where we're trying to keep track of which employees are working on which projects. And in that case, we might have a relationship that looks like this. So maybe these are small little projects and only one employee works on them, but so we want each employee to be able to work on multiple projects at the same time. So that kind of design is what we're seeing illustrated here. So again, we take a look at this overall relationship and we can read it in both directions. If we read this relationship between employee and project in this direction, that is the direction from employee to project, we would say each employee is associated with or works on many projects because this notion is many, right, it's our symbol that we use. for the concept of many so conceptually, we would say an employee works on or is associated with many projects, but if we were to read the same relationship line. In the opposite direction that is in the direction from project to employee, we would read it as each project is associated with or has just one employee, because again, this end of the line here. On that side is representing the concept of one. So conceptually, we can then easily understand how we can create a variety of different relationships between our entities. I do want to highlight once again that what we're seeing here are conceptual relationships symbols. And the reason why is one, we're not showing any cardinalities and the two with these conceptual symbols we can implement or ate something like a many to many design, even though it is infeasible to directly implement such a design in a relational database.