MySQL Database Tutorial - 6 - Getting Multiple Columns Video Lecture | MySQL (Sequential Query Language) Database Tutorial - Software Development

what is going on guys welcome to your
let's see what number it is a sixth I
believe I forget this oh I forget this
more than I should but welcome to your
sixth MySQL tutorial and in this lesson
we're gonna be going over the Select
statement a little bit more because in
the last couple tutorials what I did is
I told you guys how to retrieve one
piece of information using the Select
statement for example I taught you guys
how to retrieve that name or you could
retrieve the city and if you wanted to
retrieve more than one piece of
information you would have to write
multiple select statements or do you
well let me go ahead and show you guys
this first you can retrieve more than
one column in the same select statement
for example let's say you want to
retrieve name and zip code from
customers well you go ahead and write
name and then go ahead and write a comma
and then write the additional piece of
information you want to retrieve so as
you can see using just one select
statement
it's easier than using you know two or
three just separate the columns you want
to retrieve with a comma now let me go
ahead and type this thing explain
something now one very important thing
that you want to keep note of is this
whenever you retrieve multiple select
statements you don't put a comma after
the last one I see people do this a lot
and it's a mistake so for example since
we're retrieving two pieces of
information that means we would use one
less comma so one if we retrieved all of
these one of those six columns then that
means we would use five commas so that's
throw one less comma than columns
remember that never put a comma over the
last one so let me go ahead and copy
this first then hit go and check it out
it now retrieves both a name and zip in
the exact same select statement we don't
need multiple select statements so that
would save you having to type a whole
bunch of select statements however let's
go ahead and take a look at this
customers table again let's say that you
know okay
our boss wants us to retrieve all of the
information in this table so we say okay
boss I mean go ahead and write your
script that can do that ID we would
write something like this select ID
comma name
come address kama city take a break here
go eat some lunch kama stay calm as if
that can take a whole lot of time and
whenever we type more than one columns
then the chance that we're gonna make a
err greatly increases so let me show you
guys a little trick instead of writing
every single column whenever you need to
retrieve all of the data you can just go
ahead and write this little asterisk now
this is formally called the wild card
like symbol or whatever so I call that
the asterisks or the all statement it's
that little key above the a on your
keyboard but if you're in school and
you're taking the test make sure to call
the wild card statement so basically
what this means is whenever you need to
retrieve all of the columns you can just
go ahead and write this little asterisks
and it just is like a shortcut so now
let me go ahead and hit go and check it
out it retrieves all of the columns and
all of the rows from Roache ever table
you specify now I want to mention this I
know I didn't talk to you guys about how
to use MySQL with PHP or whenever you're
making websites or in any type of
application actually but whenever you do
you can do something like this you can
retrieve all of this or excuse me all of
the data that you want to using MySQL
and only display what you need in your
application and by application I mean
you can go ahead and retrieve all this
data but only display the name and city
on your website or something so a lot of
people just use this statement all the
time select all from customers and then
they worry about what information they
want to show the user later on but I
want to say this don't do that please
that is a big mistake that beginners do
only use what is absolutely necessary
because if you do this whenever you
select all of the information and you
don't even use some of the information
then it's going to slow down your query
or the execution of this MySQL script
well it's not really important in this
one because this is a relatively small
table but whenever you're working with a
whole bunch of data with a whole bunch
of users it can cause significant
problems and it could slow down the
website
for people it could run into you can
have something called mysql' slow
queries and then whoever your host is
for example hostgator would start
limiting my bandwidth so guys i just
want to say even though you can retrieve
a whole bunch of data and only display
what's necessary to the user please
don't do this please only select what is
ever necessary and only use this special
shortcut
whenever you absolutely need to so I
know I talked about that for a while but
guys it's a very important more
important thing I could stress oh so
anyways thank you I need to go get a
drink of water or something so anyways
I'm gonna save the rest of the
information for the next tutorial
so like I said thanks for watching I'm
gonna subscribe and I'll see you guys
then