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Goal:
"In which years was the Physics prize awarded but no Chemistry prize. (WARNING - this question is way too hard for this level, you will need to use sub queries or joins). "
Problem:
Don't know how to solve it.
The code can be found in "http://sqlzoo.net/1b.htm", headline 3a.
SELECT
distinct yr
FROM
nobel
WHERE
yr not in (select yr from nobel where subject in ('Chemistry')) AND
subject in ('Physics')
One option using subqueries. The subquery gets all the years where there was a chemistry prize which is used to to excude those years with the not in statement.
The distinct yr accounts for the fact that there could have been two prizes awarded.
There's a bunch of different ways to make this work. Take the code above and try making a join with the subquery work. That'll give you more practice with subqueries and using them in joins which is a useful thing.
Related
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CrimeData Table for 12 months
Crime Took place in Easternmost
I need to find the following:
Q.7 What type of Crime takes place in the …
(a) Easternmost ………………..
(b) Westernmost ………………..
(c) Northernmost………………..
(d) Southernmost………………..
I tried to find the crime took place in the Easternmost using the following SQL code
SELECT Max(CrimeData.Easting) AS MaxOfEasting, CrimeData.Type
FROM CrimeData
GROUP BY CrimeData.Type;
but I got more than one crime and also other Easting numbers. Can you please tell me if there are other good ways to find the solution.
Please see the attached pictures :)
Rather than using Max/Min, have a look at the TOP keyword in SQL. Some SQL might look like:
SELECT TOP 1 CD.*
FROM CrimeData CD
ORDER BY CD.Easting DESC;
Regards,
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can someone please check if this is correct?
Not sure if my answer to Q6 is correct, I am not sure if the group_by I am using is right or not, the rest I think is ok
Thanks
You are close. You need to:
Use COUNT() instead of SUM().
There's no need to use the HAVING clause.
Optionally, you can add aliases to the columns, so they become easier to read.
Your query should look like:
select a.author_id, count(*) as titles, sum(b.quantity_ordered) as units
from a join b on a.book_id = b.book_id
group by a.author_id
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Please explain some of these SQL code snippets to me:
select S.sid
from Student S
I don't know what the word "S" means after table name Student. Please give me a hand and explain.
S is an alias. Student S.
If you didn't specify an Alias, you could use:
select sid from Student
or select Student.sid from Student
The alias can be pretty much anything. E.G:
select aliasnameishere232fsdf.sid from Student aliasnameishere232fsdf
Alias's not only make query's easier to type, but can be useful for self-joins, for differentiation:
select S1.firstName, S2.firstName
from Student S1
JOIN Student S2 ON S2.someId = S1.someId
S is an alias. It's a shorter name given to Student in this query to make it easier to address.
It isn't very helpful in this particular query, but in longer and more complex queries, this technique really helps writing manageable code.
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Sql query to find out no of boys and girls in school
is it correct
select count(*)
from schooldata
group by sex;
You need sex in select as well, otherwise you can't tell which is which.
select sex, count(*) from schooldata group by sex;
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I am new to databases. And our teacher gave us pretty hard assignment. There are two tables. First table nickname is abilities(of superhero's:) ) and second table name superheros.
We have to select nick of Superhero and his average(medial) range for those who has two abilities?
Image of both tables:
Original here: http://postimg.org/image/85pqbc47n/
I will not give you solution - after all, it's homework and you have to learn something :) But I can give you an advice - try to do one task at a time
first, find those superheroes who has only 2 abilities (actually, you can do this by quering only table with abilities)
second - try to find average range of abilities for all superheroes (here you'll need join)
combine your queries
take a look at join, group by, count and having
Don't feel bad if you can't write it at first attempt, your query is not super easy, but 'm sure you can do this.
You can use HAVING and AVG() for this:
SELECT s.NickName, AVG(a.Range)
FROM abilities a
JOIN superhero s
ON a.ID_SuperHero = s.ID_SuperHero
GROUP BY s.NickName
HAVING COUNT(DISTINCT a.Abilities > 1)