Software Development Exam > Software Development Videos > MySQL (Sequential Query Language) Database Tutorial > MySQL Database Tutorial - 28 - UPDATE & DELETE
MySQL Database Tutorial - 28 - UPDATE & DELETE Video Lecture | MySQL (Sequential Query Language) Database Tutorial - Software Development
FAQs on MySQL Database Tutorial - 28 - UPDATE & DELETE Video Lecture - MySQL (Sequential Query Language) Database Tutorial - Software Development
| 1. What is the purpose of the UPDATE statement in MySQL? |  |
Ans. The UPDATE statement in MySQL is used to modify existing records in a database table. It allows you to update specific columns or values of one or multiple rows based on certain conditions.
| 2. How can I update a single column in MySQL using the UPDATE statement? | |
Ans. To update a single column in MySQL, you can use the following syntax:
UPDATE table_name
SET column_name = new_value
WHERE condition;
Replace "table_name" with the name of your table, "column_name" with the name of the column you want to update, "new_value" with the desired new value, and "condition" with the condition that specifies which rows to update.
| 3. Can I update multiple columns simultaneously in MySQL? | |
Ans. Yes, you can update multiple columns simultaneously in MySQL by including multiple column-value pairs in the SET clause of the UPDATE statement. Here's an example:
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
Replace "table_name" with the name of your table, "column1" and "column2" with the names of the columns you want to update, "value1" and "value2" with the new values for those columns, and "condition" with the condition that specifies which rows to update.
| 4. How do I delete records from a MySQL database table? | |
Ans. To delete records from a MySQL database table, you can use the DELETE statement. Here's the basic syntax:
DELETE FROM table_name
WHERE condition;
Replace "table_name" with the name of your table and "condition" with the condition that specifies which rows to delete. Be careful when using the DELETE statement as it permanently removes records from the table.
| 5. Is it possible to delete all records from a MySQL table? | |
Ans. Yes, it is possible to delete all records from a MySQL table. To do this, you can use the following syntax:
DELETE FROM table_name;
Replace "table_name" with the name of your table. This statement will remove all the records from the table, but the table structure will remain intact.
Text Transcript from Video
all right everyone welcome to your 28th
MySQL tutorial I have no idea why you
guys are still watching these total
waste of time I'm just kidding but
anyways welcome to your 28th tutorial
and now that we know how to do also
school stuff insert rows into our table
we know how to do a whole bunch of query
select statements I think it's time we
learn how to edit rows so check it out
let's say that we just inserted an item
into this website so I'm selling some I
don't know a sack of ham or something
but then I was like oh wait a minute mom
you said pudding hammock I thought you
said sack of ham now I have to sell a
fricken sack of ham well we need a way
to edit items that are already in the
database now we can do this in one of
two ways the first way is that we can
just go ahead and delete this row and
rewrite it but there's an easier more
simple way and I'm gonna show you that
right now so in order to edit a row you
use the term update I think they should
have chose edit but they chose update
instead it means the same thing now
you're saying okay what table do you
want to update well I want to update a
row from the items table so there you go
go ahead and hit items now after this
you need to say okay which piece of
information did you want to update did
you want to update the ID the name of it
maybe you wanted to change the price or
the number of bids well in order to do
that we first need to use the set
keyword now set means change basically
now after this rewrite the name of the
column or the piece of information that
we want to change so of course what was
I say a sack of ham or something I
forgot what it was
by anyways we want to change it so we
want to change the name well what do you
want to change it to just go ahead and
give it a new value using equals and
then type the new value we want to sell
a pudding hammock and if you don't know
what that is I would recommend that you
open dictionary that shiz we wanted to
actually sell pudding hammock instead of
a sack of ham so we can't just go ahead
and run this baby right now because look
what happens whenever we were to run
this it would update the items table and
it would set the name
of all of your items to pudding hammock
now unless you're running a website and
you're selling 300 pudding hammocks I
don't recommend you do this so whenever
you use the update excuse me I can't
talk
whenever you use update to edit rows it
is critical that you use a where clause
now the where clause is saying okay what
row do you want to edit well we only
want to edit where IB is equal to 106 we
only want to edit this item we don't
want to change the name of all of the
rows in our table so now let's go ahead
and run this and check it out it now
says one row affected and if we go look
at items in a sort find 106 it now
changed the name of 106 - pudding
hammock
now how awesome is that so check this
out say that we I don't know we were
maybe editing this and maybe we had to
take it down because we're not allowed
to so pudding hammocks but then we
talked to the owner of the website and
he allowed us to put it back up well
that's nice and all but why the heck did
you reset my bids to zero these are hot
items they're selling like hotcakes this
thing had like 66 bids on it well of
course we need to edit that too so if
you're saying okay not only do I want to
edit one column but I want to edit
multiple columns we can do that as well
now I'm not gonna have to type the whole
thing let me just well I might as well
change this again so let's say you know
what instead of selling pudding hammocks
I'm gonna sell for outpaced it's the
best pace trust me guys now whenever you
want to edit more than one columns again
this is pretty self-explanatory but you
just separate it with a comma now you go
ahead and write the other name of the
column for example the bids and you can
edit these two so again just like before
seperate your columns with a comma and
just write the new value of each so now
we're changing the item 106 again we're
changing the name to fraud paste and
we're gonna add 66 bids because I don't
know why not it's just an example
give me a break guys so now we go ahead
and hit go and it says one row fat
that but of course you can never trust
computers and you ever see eagle eye so
um we're gonna make sure frog paste and
bids 66 so that is not only how you
update items but also how you update an
item with multiple well you know I can't
even explain it multiple columns at once
so now I want to teach you guys about
the lead and you guys are thinking okay
next tutorial but I'm not going to teach
you in the next tutorial because delete
in how to delete rows of items for
example if we no longer want to sell
this fraud paste or we no and longer
want this beef on a stick on the website
I'm going to show you guys how to delete
this and the reason I'm not waiting for
another tutorial is because this is the
easiest thing I have ever taught anyone
in my life so in order to delete rows
just go ahead and hit delete from and
write what table do you want to delete a
row from well I want to delete from
items where ID equals 106 you guys
probably think I'm gonna type something
else after this but I'm not that's it
the only thing you're right is what row
do you want to delete and what table are
you deleting that row from now again the
where Clause is very important because
if you just say delete from items it
might delete your entire table so let me
go ahead and delete the item I'll go
ahead and delete 104 so it says do you
really want to delete okay yes I do and
it says okay I freaking delete it before
you you said okay you've even verified
it so now we got to go ahead and check
we got 106 105 104 is now deleted from
our table 103 102 101 so on and so forth
so I can't remember what that item was
but that is how you delete items from a
database and again I know a lot of you
guys are just gonna be so tempted to not
use that where clause and it's gonna
delete your whole table but hey there
you go so another thing I want to
mention this is the last thing I promise
before you know you guys can go it's
weird cat videos or something but that's
why primary keys and ID numbers are so
important because you know how in our
where clause I said delete items where
ID equals 106 well say that you just
not to use primary keys or ID numbers
because you know you just don't take my
advice well then you started this
website and a bunch of people were
selling DVDs well you want it to leave
this item right here because this is a
spammer who posted this so you said
delete where name equals DVD so yes you
ran that query and it would delete this
row too but it would delete all those
other people who also named their items
DVDs so whenever you use primary Keys
instead of giving a general name that
may delete ten or twenty other rows
accidentally you say delete item 99
because that's the primary key no other
row can have that primary ID key and you
give it an ID so that way it knows which
specific want to delete so that is the
beauty of primary keys and again that's
one little gem of information plenty
more to come in the next tutorial what
I'm gonna be doing is I'm gonna be
showing you guys how to create entire
tables it's gonna be awesome it's gonna
be amazing so thank you guys for
watching don't forget to subscribe and
add me on Google+ and I will see you
guys in the next video
MySQL tutorial I have no idea why you
guys are still watching these total
waste of time I'm just kidding but
anyways welcome to your 28th tutorial
and now that we know how to do also
school stuff insert rows into our table
we know how to do a whole bunch of query
select statements I think it's time we
learn how to edit rows so check it out
let's say that we just inserted an item
into this website so I'm selling some I
don't know a sack of ham or something
but then I was like oh wait a minute mom
you said pudding hammock I thought you
said sack of ham now I have to sell a
fricken sack of ham well we need a way
to edit items that are already in the
database now we can do this in one of
two ways the first way is that we can
just go ahead and delete this row and
rewrite it but there's an easier more
simple way and I'm gonna show you that
right now so in order to edit a row you
use the term update I think they should
have chose edit but they chose update
instead it means the same thing now
you're saying okay what table do you
want to update well I want to update a
row from the items table so there you go
go ahead and hit items now after this
you need to say okay which piece of
information did you want to update did
you want to update the ID the name of it
maybe you wanted to change the price or
the number of bids well in order to do
that we first need to use the set
keyword now set means change basically
now after this rewrite the name of the
column or the piece of information that
we want to change so of course what was
I say a sack of ham or something I
forgot what it was
by anyways we want to change it so we
want to change the name well what do you
want to change it to just go ahead and
give it a new value using equals and
then type the new value we want to sell
a pudding hammock and if you don't know
what that is I would recommend that you
open dictionary that shiz we wanted to
actually sell pudding hammock instead of
a sack of ham so we can't just go ahead
and run this baby right now because look
what happens whenever we were to run
this it would update the items table and
it would set the name
of all of your items to pudding hammock
now unless you're running a website and
you're selling 300 pudding hammocks I
don't recommend you do this so whenever
you use the update excuse me I can't
talk
whenever you use update to edit rows it
is critical that you use a where clause
now the where clause is saying okay what
row do you want to edit well we only
want to edit where IB is equal to 106 we
only want to edit this item we don't
want to change the name of all of the
rows in our table so now let's go ahead
and run this and check it out it now
says one row affected and if we go look
at items in a sort find 106 it now
changed the name of 106 - pudding
hammock
now how awesome is that so check this
out say that we I don't know we were
maybe editing this and maybe we had to
take it down because we're not allowed
to so pudding hammocks but then we
talked to the owner of the website and
he allowed us to put it back up well
that's nice and all but why the heck did
you reset my bids to zero these are hot
items they're selling like hotcakes this
thing had like 66 bids on it well of
course we need to edit that too so if
you're saying okay not only do I want to
edit one column but I want to edit
multiple columns we can do that as well
now I'm not gonna have to type the whole
thing let me just well I might as well
change this again so let's say you know
what instead of selling pudding hammocks
I'm gonna sell for outpaced it's the
best pace trust me guys now whenever you
want to edit more than one columns again
this is pretty self-explanatory but you
just separate it with a comma now you go
ahead and write the other name of the
column for example the bids and you can
edit these two so again just like before
seperate your columns with a comma and
just write the new value of each so now
we're changing the item 106 again we're
changing the name to fraud paste and
we're gonna add 66 bids because I don't
know why not it's just an example
give me a break guys so now we go ahead
and hit go and it says one row fat
that but of course you can never trust
computers and you ever see eagle eye so
um we're gonna make sure frog paste and
bids 66 so that is not only how you
update items but also how you update an
item with multiple well you know I can't
even explain it multiple columns at once
so now I want to teach you guys about
the lead and you guys are thinking okay
next tutorial but I'm not going to teach
you in the next tutorial because delete
in how to delete rows of items for
example if we no longer want to sell
this fraud paste or we no and longer
want this beef on a stick on the website
I'm going to show you guys how to delete
this and the reason I'm not waiting for
another tutorial is because this is the
easiest thing I have ever taught anyone
in my life so in order to delete rows
just go ahead and hit delete from and
write what table do you want to delete a
row from well I want to delete from
items where ID equals 106 you guys
probably think I'm gonna type something
else after this but I'm not that's it
the only thing you're right is what row
do you want to delete and what table are
you deleting that row from now again the
where Clause is very important because
if you just say delete from items it
might delete your entire table so let me
go ahead and delete the item I'll go
ahead and delete 104 so it says do you
really want to delete okay yes I do and
it says okay I freaking delete it before
you you said okay you've even verified
it so now we got to go ahead and check
we got 106 105 104 is now deleted from
our table 103 102 101 so on and so forth
so I can't remember what that item was
but that is how you delete items from a
database and again I know a lot of you
guys are just gonna be so tempted to not
use that where clause and it's gonna
delete your whole table but hey there
you go so another thing I want to
mention this is the last thing I promise
before you know you guys can go it's
weird cat videos or something but that's
why primary keys and ID numbers are so
important because you know how in our
where clause I said delete items where
ID equals 106 well say that you just
not to use primary keys or ID numbers
because you know you just don't take my
advice well then you started this
website and a bunch of people were
selling DVDs well you want it to leave
this item right here because this is a
spammer who posted this so you said
delete where name equals DVD so yes you
ran that query and it would delete this
row too but it would delete all those
other people who also named their items
DVDs so whenever you use primary Keys
instead of giving a general name that
may delete ten or twenty other rows
accidentally you say delete item 99
because that's the primary key no other
row can have that primary ID key and you
give it an ID so that way it knows which
specific want to delete so that is the
beauty of primary keys and again that's
one little gem of information plenty
more to come in the next tutorial what
I'm gonna be doing is I'm gonna be
showing you guys how to create entire
tables it's gonna be awesome it's gonna
be amazing so thank you guys for
watching don't forget to subscribe and
add me on Google+ and I will see you
guys in the next video
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About this Video
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Dec 23, 2024 Last updated |
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