text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
in our database? | 3,623.74 | 0.85 |
Let's try that one out too and
see how that works with ASC | 3,624.59 | 3.2 |
for ascending and DESC for descending. | 3,627.79 | 2.97 |
So I'll go back to my terminal. | 3,630.76 | 1.59 |
And I'll demonstrate here how
we can use this for some text. | 3,632.35 | 3.36 |
So let's try to simply sorting our
books alphabetically for, let's say, | 3,635.71 | 5.07 |
our library. | 3,640.78 | 1.02 |
I'll say SELECT "title"
from "longlist," Enter. | 3,641.8 | 5.1 |
And I want to order by
title, just plain and simple. | 3,646.9 | 3.31 |
And then hit Semicolon. | 3,650.21 | 1.38 |
Let's see what happens. | 3,651.59 | 1.16 |
I'll hit Enter. | 3,652.75 | 1.41 |
And now I'll see that
these books are ordered. | 3,654.16 | 3.54 |
But they seem to be
ordered alphabetically. | 3,657.7 | 2.28 |
So here, we have some titles
lower in the alphabet. | 3,659.98 | 3.72 |
And up here, we have titles
earlier in the alphabet. | 3,663.7 | 2.62 |
So by default ORDER BY seems
to order alphabetically. | 3,666.32 | 4.46 |
If I change that default, though,
from ascending to descending, | 3,670.78 | 4.29 |
let's see what happens. | 3,675.07 | 1.89 |
I'll go back over here. | 3,676.96 | 1.29 |
And I'll try the same
query but now using DESC. | 3,678.25 | 4.74 |
SELECT "title" from "longlist." | 3,682.99 | 1.77 |
ORDER BY "title" now
in descending order. | 3,684.76 | 4.35 |
Hit Enter. | 3,689.11 | 1.29 |
And now I'll see these titles
in reverse alphabetical order. | 3,690.4 | 4.23 |
So notice how earlier on, we have
titles that are lower in the alphabet. | 3,694.63 | 4.56 |
But down below, we have titles that
are earlier in the alphabet here. | 3,699.19 | 3.55 |
So you can use ORDER
BY with these texts. | 3,702.74 | 3.59 |
But you then have to specify whether
you want it in alphabetical order | 3,706.33 | 3.36 |
or in reverse alphabetical order. | 3,709.69 | 4.27 |
OK, so let's show a
few other concepts here | 3,713.96 | 4.74 |
we can use alongside of these orderings. | 3,718.7 | 3.04 |
One thing we could also do is
try to find more information | 3,721.74 | 4.34 |
about the ratings of these books. | 3,726.08 | 1.77 |
So let's say I want not
just to order these books | 3,727.85 | 3.12 |
but try to find the average rating,
or to try to find the number of books, | 3,730.97 | 4.74 |
or try to find let's say maybe the sum
of my total votes on each of my books. | 3,735.71 | 5.37 |
Well, for this, we could
introduce some new concepts, | 3,741.08 | 3.78 |
these ones called SQL's
aggregate functions. | 3,744.86 | 4.2 |
These allow us to take a whole set of
rows and return not each of those rows | 3,749.06 | 6.33 |
individually. | 3,755.39 | 1.17 |
But instead, in this case, one number
based on the values in those rows. | 3,756.56 | 5.73 |
You could imagine trying to
count the number of rows you have | 3,762.29 | 3.06 |
or take the average
of the number of rows, | 3,765.35 | 2.61 |
or take the average of let's
say a rating, for instance. | 3,767.96 | 2.67 |
Finding the minimum rating
of the maximum rating | 3,770.63 | 2.07 |
or finding the sum of some votes. | 3,772.7 | 2.49 |
And we'll see each of
these in action here. | 3,775.19 | 3.04 |
Let's go back to our terminal,
try some of these out. | 3,778.23 | 3.23 |
I will try, in this case
first trying to find | 3,781.46 | 4.26 |
the average rating from my longlist. | 3,785.72 | 2.9 |
Well, I just from experience,
and as you now know too, | 3,788.62 | 3.43 |
I can try to find the
average of some column | 3,792.05 | 2.82 |
by using the AVG aggregate function. | 3,794.87 | 3.52 |
So I'll say SELECT not
just rating in this case | 3,798.39 | 4.58 |
but select the average
rating FROM "longlist." | 3,802.97 | 4.95 |
Notice how in this case, I'm using this
kind of syntax, where I take rating, | 3,807.92 | 5.64 |
my column I want to aggregate or
to sum up or to average like this. | 3,813.56 | 4.77 |
And I apply the function
by saying its name | 3,818.33 | 3.18 |
followed by some parentheses
around that column name. | 3,821.51 | 3.67 |
So this will return to
me not all of the rating | 3,825.18 | 2.45 |
rows but the average of the
rating rows in one single cell. | 3,827.63 | 4.8 |
Let me try this. | 3,832.43 | 1.65 |
I'll come back, and I
will then hit Enter. | 3,834.08 | 2.91 |
And I'll see this is the average rating. | 3,836.99 | 3.45 |
We have 3.7537179471795 is our
average rating for all of these books. | 3,840.44 | 8.28 |
But of course, this isn't great. | 3,848.72 | 3.06 |
What might I want to do if I was
going to show this to somebody else? | 3,851.78 | 4.14 |
I could probably improve the
presentation of this in some way. | 3,855.92 | 5.02 |
So I could probably round
this result. I have 3.75371, | 3,860.94 | 4.7 |
we can probably stop after
two decimal points, right? | 3,865.64 | 2.88 |
Just simply like 3.75. | 3,868.52 | 2.1 |
So I could introduce some new keyword
here, this one around the results. | 3,870.62 | 4.71 |
Let me show you this one in action. | 3,875.33 | 2.52 |
I'll come back, and I'll try
not just select average rating | 3,877.85 | 3.69 |
but select the rounded average rating. | 3,881.54 | 2.83 |
So I'll say SELECT ROUND and then
take average of "rating" and round | 3,884.37 | 7.55 |
to 2 decimal points FROM
"longlist" Semicolon. | 3,891.92 | 6.3 |
So now this query decides to first
find the average of the rating column. | 3,898.22 | 6.69 |
Then take the result and round
it using two decimal points. | 3,904.91 | 5.95 |
Notice how round takes two inputs
or two arguments, the first one | 3,910.86 | 3.65 |
being the rating, the average
rating, the second one being number | 3,914.51 | 3.99 |
of decimal points to round, 2. | 3,918.5 | 1.8 |
And we complete our query in the way we
usually do by saying FROM this table. | 3,920.3 | 4.33 |
So let's try this one
to figure this out. | 3,924.63 | 2.24 |
I'll come back. | 3,926.87 | 0.75 |
And I'll hit Enter. | 3,927.62 | 1.5 |
And now I'll see we do get back 3.75. | 3,929.12 | 3.99 |
But there is still one
thing to improve here. | 3,933.11 | 2.61 |
When I write this query, I
see this ugly title name-- | 3,935.72 | 3.87 |
ROUND average "rating" comma 2. | 3,939.59 | 2.4 |
I wouldn't send this to my
boss or somebody else who I | 3,941.99 | 2.785 |
work for or maybe even a friend, right? | 3,944.775 | 1.625 |
I want to make sure it's pretty
so they can read it correctly. | 3,946.4 | 2.77 |
So what could I do then to
try to make this prettier? | 3,949.17 | 4.18 |
I could maybe rename this column. | 3,953.35 | 1.74 |
I could try to take this and make
it not just this ugly mess of SQL | 3,955.09 | 4.59 |
keyword but to give it some
name I could use instead. | 3,959.68 | 3.13 |
So for this, we'll
introduce a brand new one-- | 3,962.81 | 2.36 |
new brand new keyword called AS. | 3,965.17 | 2.13 |
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