SQL Tutorial - 4: Things You Need To Know About Tables Video Lecture | Microsoft SQL for Beginners - Database Management

hello guys welcome to my channel this is
the fourth tutorial in this course and
in this tutorial we are going to have a
look at another boring presentation
right and I just don't know why I make
such bowing presentations but anyway
we're gonna check out a few concepts and
some of the things are we gonna talk
about in this in this tutorial we've
already talked about them little bit in
the previous tutorials but you know
there's no harmony visiting some
important concepts so anyway the first
slide asks us a question what is a table
and we probably know by now what your
table is but then again the definition
of a table is that it is a database
object that is composed of rows and
columns so firstly what I mean by the
fact that a table as a database object
is that when you create tables you have
to put your tables within databases
right so tables cannot exist outside
databases they have to be stored within
databases and then tables have some kind
of a structure right so they've got rows
and they've got columns and we've seen
how an excel sheet is like a table right
because it's got you know so many cells
and it's got rows and columns and at the
intersection of rows and columns you
have cells and in those cells you put in
information right so an excel sheet is
an excellent example of a table and then
in SQL a table is created using the
create table command and we're not going
to use the create table command in this
tutorial but we are going to understand
it you know in depth later on in the
course but I just wanted to mention it
to you guys that we create tables in SQL
using commands right and then in the
next slide I have an example of a table
for you guys so this table has
information about tennis players and
their ranking so you have three fields
the first ones called rank the second
one is name and the third one is age and
the rank field obviously holds the
rankings of tennis players from 1 to 10
the name field holds the names of tennis
players in the H field holds the ages
right so rank one well no Mac joke which
is at top and he's 26 years old and then
on rank 2 you have refiner on how the
hell did I misspell to file and I was
named that's like very disturbing error
and Roger Federer by the way has slipped
number 7 in case you don't know and I'm
a huge Roger Federer fan but that's not
the reason why I misspelled Rafa and I
was named a fan of Rafa too so please
strong fans don't take offense you know
this was just a typo so anyway you've
got all this information and you always
have to give some name to your tables in
SQL right so you could call this table
anything like tennis underscore rankings
or you know rankings underscore tennis
or whatever right so anyway on the next
slide I have another question for you
guys and this one is what is a field a
field is a column in a table that is
supposed to provide specific information
about all the records in the table and
in layman's terms what this means is
that rank here is a field right and name
is another field and age is another
field so all the columns that are
associated with the rank field are going
to hold rankings of tennis players and
all the columns that are associated with
the name field are going to hold names
of tennis players and all the ones that
are associated with age are going to
hold ages right so you cannot have email
addresses in the H field right if you
put a constraint that it's going the
data type of this field is going to be
integer then you cannot have characters
in here so you know field are the
headings that you see when you create a
table right so this is this is the
reason why I am discussing these things
with you guys is because we will be
using all these terms a lot right so we
are going to talk about rows and columns
and records and fields way too much in
this course so I want you guys to you
know just understand all these things
you know at the very beginning of the
course and in the previous table the in
the previous slide so the rank name and
age these three things are fields and
so the next slide asks us yet another
question what is a record and a record
is a row in a table and the table seen
earlier has ten records or ten rows
right so each row has you know three
columns and in the first column you know
rank of a tennis player in the second
column you have tennis players name the
third one you have the tennis players
age right and there are ten rankings so
corresponding to the 10 rankings you
have ten rows right and a record is also
known as a horizontal entity of a table
you don't need to remember this but you
know some people might be writing exams
on SQL so you know you can find
questions such as these like what is the
difference between horizontal entity in
vertical entity of a table so column is
a vertical entity and a record is a
horizontal entity and the this is in
fact what we're going to talk about in
in the next slide what is a column so a
column is a vertical entity in a table
that contains information associated
with a specific field so in the previous
in the last last slide what was the last
last last last last
anyway the table that we saw for tennis
players we have all these columns in it
so the name name is the field and then
you have you know all the information
stored associated with names in columns
in the table right so Novak Djokovic
Rafael Nadal and even all these are
names of tennis players and you have you
know similar information as I said you
know information about names arranged in
columns right and next we are going to
talk about null values so what is a null
value you would hear a lot of people say
that a null value is 0 or null value is
the space character but that's not true
right null value simply means nothing
right it is no value so if you are
inserting data in a table and if you do
not provide value for cells the cell is
said to contain a null value and what I
mean is if you're populating a table in
your database if you're putting
information in it and if for a
particular cell or a particular column
in a row you do not want to provide any
input you do not want to put any
information
then you just don't type in anything
right you don't put in a space character
you don't put in zero or you don't put
in any alphabet or any special character
you just don't put anything and that
absence of information that absence of
data is actually null value right so
it's unknown nobody knows what that is
so that's why we call it null value so
anyway thank you so much for watching
this tutorial that's the end of the
presentation and well we are moving
towards the business end of this course
so in the next tutorial we are going to
get our hands dirty with three very
simple SQL commands we're going to learn
to create databases drop databases and
also user bases so thank you so much for
watching this tutorial I'm gonna see you
in the next one
please subscribe to my channel in case
you have already and I see you