Tutorial 15 - ALTER TABLE Video Lecture | Postgresql: A Complete Tutorial - Database Management

hello guys welcome to our tutorial of
course we SQL in this tutorial we will
learn how to alter our tables in
PostgreSQL so to begin that I'll be
using the table that you created that is
the company table so first of all I'll
tell you how to add a column in our
existing database so you could do it by
the SQL syntax I will show you you will
just add alter table company add this is
the column name that you gonna add that
is gender and now you will enter the
datatype lettuce character of size 1 so
you could see this this is return
successfully and if you see select star
from company you would see that this
column has been added in my table you
see this this is not defined right now
because I have not put any values so you
could put in any values in this so yeah
so the next thing that we are going to
do is we going to drop this column you
could do it by alter table company drop
column gender so run this and you see it
returned successfully again and if you
check it select star from company you
would see that this column has been gone
so this is the way you add and delete
columns by SQL query in PostgreSQL next
next thing that I am going to show you
is how to add a primary key by SQL query
if you have not added it in your in your
development period or the time when you
created your table you have not ready
primary key so you could add a primary
key at a later stage by this query by
ordinal table that is alter table
company add constraint that is the name
of the key that your own gift suppose
I'll give it primary or primary pry and
do it right
primary key and it will write the ID
that is primary key that is my ID would
be my primary key so you would execute
this and run successfully so you could
just check it in your properties of the
table that this has been added at the
primary key I will show you you put up
would open your page admin and just
click on properties and just click on
constraints and you would see that I
have a constraint name pry that is the
primary key so next I'm going to show
you how to remove a primary key by
programming there is a alter table
company drop constraint pry that was the
primary key that I defined the name of
the constrain once play so you could
just remove it by its constraint name
and you would see it has removed so now
if you would check the properties you
would see that to refresh it and you
will see that it is gone now
and you could see that is not there so
this was all for the alter table now the
simplest way you could add or delete any
columns in your table that is you could
do it by a new column here and you could
just write the name that is judo right
gender and datatype you could create
trust cache character and you will see
that it has been created and the
simplest way to delete is the
right-click on it and just delete it and
the simplest way to add a primary key is
to click on properties go to constraints
and in the primary key you can click on
add and you would write try
and for the columns just add ID and
click Add that's ok and ok so you would
see that the primary key has been added
so this is the simplest way or the
graphical way you could do it so thank
you for watching strudle subscribe for
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