Tutorial 34 - Left and Right Outer Joins Video Lecture | Postgresql: A Complete Tutorial - Database Management

hello boys welcome to our return of
PostgreSQL in the true dilemma to talk
about the left and the right outer join
so what happens in case of an outer join
in so first of all let's discuss about
outer join
so PostgreSQL or any SQL it basically
supports three types of outer join so
they are nothing but an extension of the
inner join only so three types of outer
join that the SQL supports is the left
right and the full outer join so in case
of left outer join what happens that an
inner join is performed first of all the
inner join that we learned about in the
previous tutorial so if you did not
watch it you should watch it first and
then watch this drill so in the last
tutorial so what happens is that in an
outer join first of all an inner join is
conducted then as we discussed in an
inner join the rows that match the
columns that have the same value in both
the tables they get combined with each
other so that was the purpose of the
inner join so in outer join what happens
is that first of all the inner join is
conducted and the values that do not
match replaced by the normal then our
values so let me tell you by an example
like suppose I have the company table
and I have the department table so in
the last tutorial we learned that we had
only one value that is the two that
matched with the the department table
that was engineering so what would
happen in case of left outer join that
if I left outer join company with the
department table then these values would
be complete like these values would be
complete and the value that won't match
in the department table would be filled
with null values so let me show you an
demo so
so you can see that select name age
address department from company and we
will be making a left outer join
department and the join condition that
is company not highly equal to
department dot ID so as you can see now
here that the company table was left
outer join on the department table so a
very easy way to remember this is that
anything that would be on the left like
the company table here is on the left so
its detail is going to be fully
displayed or completely displayed and
the table and the table that is on the
right side that is the department table
if this condition does not match at any
situation then these values would be
filled by a null so left outer join
means the company table that is on the
left hand side is going to be the full
table and the department table would be
tested for the join condition and if it
does not match it will be filled with
null values so here as you could see
only the number two condition matched so
the results are full air and the rest of
the conditions did not match the ID
values did not match so it will it is
filled by the null values here so this
was all about the left outer join
now you could assume what right outer
join would be in case of right outer
join you need to just replace left by
right and the whole scenario is
completely interchanged now what happens
is the table that is on the right would
be fully displayed and the table that is
on the left is checked for the join
condition and if it does not match then
the company table would be empty or will
be filled with null values and the table
on the right hand side would always be
complete so you could see that table on
the right is fully complete and table on
the left is filled with null values
because the conditions did not match so
in case of outer join we have at least
one row so this was all for the outer
join in the next tutorial I'm going to
talk about the full outer join so thank
you for enroll subscribe for more and
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