Original subtitles

‫All right, so columns, we already kind of talked about this when we defined what a table was, because

‫a table is a collection of columns and rows and each column has a specific data that it wants to store.

‫For instance, here, last name, we're being very specific about what we want to store.

‫And each and every column has a name.

‫But columns are a bit more complicated than that, they have more going on than seemingly just being

‫a place to store a specific type of data.

‫Now, what do I mean by that?

‫Well, one single column is called the column.

‫We know that.

‫But what would we call the collection of all the columns?

‫Well, that's what we would call the degree.

‫We call that the degree of the relation.

‫If we were to take a table and we were to say, OK, what is it we're storing in the table?

‫What we would say, like we're storing multiple columns, that's that's one way of saying it.

‫Or you could say the degree of the relation is I'd first name, last name, sex and date of birth.

‫It's a very theoretical thing to say.

‫Nevertheless, it's the term that we used to call out the collection of columns and each and every column

‫stores a specific type of data.

‫Here we can see that last name stores the last name and that sex stores male, female or otherwise.

‫And that date of birth follows a very strict year, month, day.

‫Well, when we talk about what a column can store, we call that the domain or the constraint we're

‫seeing, OK, in date of birth, we can only store dates.

‫So we have a lock here symbolizing you are constraining the data you're seeing only put this in this

‫field.

‫So we're saying and date of birth only put dates and the same we could say for sex only put one singular

‫letter M or F or otherwise.

‫So we're being very specific about the domain of the data, the domain of the column.

‫That's what we call domain.

‫It's the constraint of the data.

‫It's what can go in here.

‫And another way of talking about columns is saying, well, my table has these attributes with these

‫constraints.

‫So there's very theoretical ways of talking about this and all of these are used interchangeably.

‫You could say attributes, you could say degree of the relation.

‫You could see columns, you could see my columns have these constraints or these domains.

‫And the only reason I'm pointing these out to you is because when you go into the real world and you

‫talk to people that are making databases, they may use this terminology interchangeably.

‫And all you need to know is that a lot of them have synonyms or simpler ways of seeing them.

‫You could say call, you could say the table has these attributes.

‫You could say the table has this degree of relation being it.

‫First name, last name, sex, date of birth.

‫You could say one of my columns has these constraints or my column has this domain being date time or

‫a single letter.

‫So all of these are very important nuances to take into consideration.

‫Now, let's back that up a bit, we said.

‫Every table has a column, multiple columns, or you can have a singular column, but mostly you'll

‫have multiple columns and so every table has columns.

‫Columns are also called attributes, and the collection of columns is called the Degree.

‫And each and every column may or may not enforce a specific type of data to be saved in it, you could

‫see it can be only numbers.

‫Date of birth can only be daytime.

‫We call these constraints or the domain of the attribute attribute domains, so to speak.

‫Let's keep it simple and call them constraints because we're constraining the data to be a certain type.

‫All right, now that we know that, let's take a closer look at Rose and all the specifics around them.