Software Development Exam > Software Development Videos > MySQL (Sequential Query Language) Database Tutorial > MySQL Database Tutorial - 32 - Views
MySQL Database Tutorial - 32 - Views Video Lecture | MySQL (Sequential Query Language) Database Tutorial - Software Development
FAQs on MySQL Database Tutorial - 32 - Views Video Lecture - MySQL (Sequential Query Language) Database Tutorial - Software Development
| 1. What is a view in MySQL? |  |
Ans. A view in MySQL is a virtual table that is derived from the result of a query. It does not store any data on its own but presents data from one or more tables in a structured manner.
| 2. How can I create a view in MySQL? | |
Ans. To create a view in MySQL, you can use the CREATE VIEW statement followed by a unique name for the view and the SELECT statement that defines the view's data. For example, "CREATE VIEW my_view AS SELECT column1, column2 FROM my_table;"
| 3. Can I update data in a MySQL view? | |
Ans. Yes, you can update data in a MySQL view under certain conditions. The view must be updatable, meaning it must meet specific criteria such as not containing certain constructs like GROUP BY or DISTINCT. Additionally, the view must reference only one base table.
| 4. Can I delete rows from a MySQL view? | |
Ans. No, you cannot directly delete rows from a MySQL view. However, you can delete rows from the underlying base table that the view is derived from, and the changes will be reflected in the view.
| 5. How can I drop a view in MySQL? | |
Ans. To drop a view in MySQL, you can use the DROP VIEW statement followed by the name of the view you want to remove. For example, "DROP VIEW my_view;". This will permanently delete the view and its definition from the database.
Text Transcript from Video
alright guys welcome to your 30 second
lesson and in this lesson I want to talk
to you guys about something called views
now views are kind of tricky but once
you get the hang of them you're going to
be able to do some amazing things with
them and they're going to save you a
whole bunch of time so definitely pay
attention in this tutorial because it's
going to be a good one now
views kind of think of them right now as
temporary tables now remember this views
don't contain any real data they're just
holding data from other tables so that's
all a view is a view into another table
so let me give you guys an example of
when you would use a view say you had a
website like eBay and you had all of
these items and on your home page you
wanted to show the items that have the
most bids the hottest items so what you
would do is you just go ahead and run a
query sort by bids and show the top ten
most bitted items so let's go ahead and
run a query to do that we'll go ahead
and select ID name and the number of
bids from items and we'll just go ahead
and in order to show the top ten which
is order by the number of bits so get
highest the lowest and in order to do
that we need of course descending
highest lowest and say we only want ten
we only want the 10 most fitted items so
let's go ahead and run this query and
make sure it works so clearly as we can
see what this query returns is the top
10 most bitted items but check this out
we not only want to put this on the home
page but maybe on every users page we
want to run this query on so they can
see the most top 10 bitted items and
then maybe we're going to make a little
app so people can put it on their own
page and I don't know we just want to
run this query a bunch of times so what
we can do is every time we want to show
the user the top 10 most fitted items
for our website we can go ahead and run
this query again or we could use a view
now let me show you guys how to make a
view out of this query what you would do
and this is how I do it this is probably
the easiest way to make a view go ahead
in the
run your query and make sure it works
and then once you have your query set up
how you want it to go ahead and just hit
enter and bump it down online now at the
top line go ahead and write create view
and then go ahead and name your view and
remember a view is pretty much like a
temporary table so I'm just going to go
ahead and name this view something like
most bids and then go ahead and write as
so we're pretty much saying go ahead and
create a temporary table called view
name it most bids and as the data just
go ahead and use the data from this
query right here so now go ahead and hit
go and it says okay we created it now as
you can see it creates a view on our
left-hand side and if you can tell by
the little icon a view is different from
a table because there is actually no
data inside this view the data that
you're seeing is actually the data that
exists inside items now this is good for
a couple reasons first of all whenever
the items change up maybe you know it's
a week later and all the items are sold
and we get new items with the
high-speeds so do the items in the most
bids view this is pretty much a dynamic
table it updates automatically and
therefore it's better than creating a
new table because check it out if we
were to just create an entirely new
table out of the top 10 items in items
then every time those items change we
would need to update the new table but
with a view a view gets updated
automatically whenever you run this
query it's going to take the top 10 most
fitted items at the time so that's
pretty much a cool thing whenever the
items table changes so does its view so
that's cool thing it saves you from
having to rework rewrite their entire
table every time you you know want to
update your table so pretty much just
remember that a view is dynamic and
updates automatically any times the
infer anytime the information in the
items table changes so I know it's kind
of hard to get used to but well that's
it views are kind of complicated at
first but once you get the hang of them
you'll be good now another thing and
maybe this will give you guys a better
idea of when you would use views say
that you know in our example oh man it
must spend like 15 tutorials ago I said
that you can maybe make a new table or
even a new column to have the properly
formatted mailing address because for
example whenever you want to mail
something to someone in the United
States you write the name of their city
and then their state separated by a
column but if we just use the data
straight from here there's no way that
you can use a column so what we can do
is we could actually add a temporary
column onto here or we can Joe go ahead
and just add a view so let me go ahead
and turn this baby into a new view so go
ahead and SQL in let's run our query
first so what we want to do is we want
to tie the city and state together so
city comma state in a proper mailing
format so what we do is select and
remember that concat function it takes
pretty much three things and ties it
together or any number of things
actually
so City and then after this I'm just
going to add a comma with a space after
it and then add state so for example it
would say armed Las Vegas Nevada or
something like that and I'm just going
to go ahead and write as address from
users now remember whenever you use the
as keyword it pretty much gives it a
nickname so let's go ahead and see what
this baby does now what it does is it
makes an entirely new column called
address by taking the old city adding a
comma after in a space and then writing
the state so say that we actually wanted
to save this address not only as a
temporary column but we want it to save
it as a new view so go ahead to where
you where you wrote your query and right
above it just go ahead and write create
view and now remember a view is pretty
much a temporary table so give a
temporary table name instance this we're
using this for a mailing address I'll
just go ahead and write mailing as and
under your as just go ahead and write
that query that we had before so what
this is going to
- is it's going to create a temporary
table or review called mailing and the
information that's going to be inside
that table is whatever we selected in
this query right here so go ahead and
hit go and check it out on the left hand
side if we click to browse our table or
view we can see that we now have our
properly formatted address now you guys
are probably saying okay so why wouldn't
you just make a temporary column well
whenever you have a view you can treat
it just like you would a table for
example you know how we could you know
of course run select queries on items
and users we can also run basic select
queries on these new views for example
if we go ahead and select if I can type
select name and bids from most bids what
this is going to do is it's going to
select the name and the number of bids
from our most bids view now remember our
most bids view is the one we made in our
first example which took the top ten
most bidded items and put them into an
entirely new table so let's go ahead and
run this query and so we've got the top
ten most bidded items how awesome is
that
so basically the thing you have to
remember is views do not store any data
themselves that is one benefit they have
over making a duplicate table for
example that would store the top ten
items because they don't store any
additional data they just show you data
from other tables and that's why they
don't take up any extra memory it's
basically a shortcut for having to
retype a query each and every time you
want the top ten items or anything else
for example and I know I showed you guys
some examples in this tutorial that were
probably pretty useless but trust me
views can come in handy especially when
you have queries that you run quite
often duplicate queries or you know
you'll figure it out whenever you're
programming but for this tutorial that's
all I have for you I bet you guys are
probably sick about hearing of views so
anyways thank you guys for watching
don't forget subscribe me and I'll see
you guys in the next lesson
lesson and in this lesson I want to talk
to you guys about something called views
now views are kind of tricky but once
you get the hang of them you're going to
be able to do some amazing things with
them and they're going to save you a
whole bunch of time so definitely pay
attention in this tutorial because it's
going to be a good one now
views kind of think of them right now as
temporary tables now remember this views
don't contain any real data they're just
holding data from other tables so that's
all a view is a view into another table
so let me give you guys an example of
when you would use a view say you had a
website like eBay and you had all of
these items and on your home page you
wanted to show the items that have the
most bids the hottest items so what you
would do is you just go ahead and run a
query sort by bids and show the top ten
most bitted items so let's go ahead and
run a query to do that we'll go ahead
and select ID name and the number of
bids from items and we'll just go ahead
and in order to show the top ten which
is order by the number of bits so get
highest the lowest and in order to do
that we need of course descending
highest lowest and say we only want ten
we only want the 10 most fitted items so
let's go ahead and run this query and
make sure it works so clearly as we can
see what this query returns is the top
10 most bitted items but check this out
we not only want to put this on the home
page but maybe on every users page we
want to run this query on so they can
see the most top 10 bitted items and
then maybe we're going to make a little
app so people can put it on their own
page and I don't know we just want to
run this query a bunch of times so what
we can do is every time we want to show
the user the top 10 most fitted items
for our website we can go ahead and run
this query again or we could use a view
now let me show you guys how to make a
view out of this query what you would do
and this is how I do it this is probably
the easiest way to make a view go ahead
in the
run your query and make sure it works
and then once you have your query set up
how you want it to go ahead and just hit
enter and bump it down online now at the
top line go ahead and write create view
and then go ahead and name your view and
remember a view is pretty much like a
temporary table so I'm just going to go
ahead and name this view something like
most bids and then go ahead and write as
so we're pretty much saying go ahead and
create a temporary table called view
name it most bids and as the data just
go ahead and use the data from this
query right here so now go ahead and hit
go and it says okay we created it now as
you can see it creates a view on our
left-hand side and if you can tell by
the little icon a view is different from
a table because there is actually no
data inside this view the data that
you're seeing is actually the data that
exists inside items now this is good for
a couple reasons first of all whenever
the items change up maybe you know it's
a week later and all the items are sold
and we get new items with the
high-speeds so do the items in the most
bids view this is pretty much a dynamic
table it updates automatically and
therefore it's better than creating a
new table because check it out if we
were to just create an entirely new
table out of the top 10 items in items
then every time those items change we
would need to update the new table but
with a view a view gets updated
automatically whenever you run this
query it's going to take the top 10 most
fitted items at the time so that's
pretty much a cool thing whenever the
items table changes so does its view so
that's cool thing it saves you from
having to rework rewrite their entire
table every time you you know want to
update your table so pretty much just
remember that a view is dynamic and
updates automatically any times the
infer anytime the information in the
items table changes so I know it's kind
of hard to get used to but well that's
it views are kind of complicated at
first but once you get the hang of them
you'll be good now another thing and
maybe this will give you guys a better
idea of when you would use views say
that you know in our example oh man it
must spend like 15 tutorials ago I said
that you can maybe make a new table or
even a new column to have the properly
formatted mailing address because for
example whenever you want to mail
something to someone in the United
States you write the name of their city
and then their state separated by a
column but if we just use the data
straight from here there's no way that
you can use a column so what we can do
is we could actually add a temporary
column onto here or we can Joe go ahead
and just add a view so let me go ahead
and turn this baby into a new view so go
ahead and SQL in let's run our query
first so what we want to do is we want
to tie the city and state together so
city comma state in a proper mailing
format so what we do is select and
remember that concat function it takes
pretty much three things and ties it
together or any number of things
actually
so City and then after this I'm just
going to add a comma with a space after
it and then add state so for example it
would say armed Las Vegas Nevada or
something like that and I'm just going
to go ahead and write as address from
users now remember whenever you use the
as keyword it pretty much gives it a
nickname so let's go ahead and see what
this baby does now what it does is it
makes an entirely new column called
address by taking the old city adding a
comma after in a space and then writing
the state so say that we actually wanted
to save this address not only as a
temporary column but we want it to save
it as a new view so go ahead to where
you where you wrote your query and right
above it just go ahead and write create
view and now remember a view is pretty
much a temporary table so give a
temporary table name instance this we're
using this for a mailing address I'll
just go ahead and write mailing as and
under your as just go ahead and write
that query that we had before so what
this is going to
- is it's going to create a temporary
table or review called mailing and the
information that's going to be inside
that table is whatever we selected in
this query right here so go ahead and
hit go and check it out on the left hand
side if we click to browse our table or
view we can see that we now have our
properly formatted address now you guys
are probably saying okay so why wouldn't
you just make a temporary column well
whenever you have a view you can treat
it just like you would a table for
example you know how we could you know
of course run select queries on items
and users we can also run basic select
queries on these new views for example
if we go ahead and select if I can type
select name and bids from most bids what
this is going to do is it's going to
select the name and the number of bids
from our most bids view now remember our
most bids view is the one we made in our
first example which took the top ten
most bidded items and put them into an
entirely new table so let's go ahead and
run this query and so we've got the top
ten most bidded items how awesome is
that
so basically the thing you have to
remember is views do not store any data
themselves that is one benefit they have
over making a duplicate table for
example that would store the top ten
items because they don't store any
additional data they just show you data
from other tables and that's why they
don't take up any extra memory it's
basically a shortcut for having to
retype a query each and every time you
want the top ten items or anything else
for example and I know I showed you guys
some examples in this tutorial that were
probably pretty useless but trust me
views can come in handy especially when
you have queries that you run quite
often duplicate queries or you know
you'll figure it out whenever you're
programming but for this tutorial that's
all I have for you I bet you guys are
probably sick about hearing of views so
anyways thank you guys for watching
don't forget subscribe me and I'll see
you guys in the next lesson
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Dec 22, 2024 Last updated |
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