Given below are two relation schemas:
Book(id, title, author, pubid, year, price, referid)
Publisher(pubid, pubname, headoffice, contact)
'id' is the primary key for Book and pubid is the primary key for 'Publisher' as well as a foreign key.
Q. Find the book id, title, referenced title and referenced publisher name.
help me answer this query...I'm trying hard but to no avail
This seems like a homework question and not like you've invested much time into solving this query on your own but this should get you started. Please edit your question to clarify if it's something more specific you're having issues:
SELECT
Book.id,
Book.title,
Publisher.pubname
FROM Book
INNER JOIN Publisher
ON Book.pubid = Publisher.pubid
This query should do
SELECT Book.id, Book.title, Refbook.title, Refpub.pubname
FROM Book
LEFT JOIN Book AS Refbook ON Book.referid = Refbook.id
JOIN Publisher AS Refpub ON Refpub.pubid = Refbook.pubid
For the next time, please give example data and a result you're looking for
Related
Just not sure what I need to do here. I have to count the total movies based off a certain production company, so the question is this:
How many movies in the database were produced by Pixar Animation Studios?
This is my SQL code so far, I work off Jupyter:
select movies.movie_id, movies.title, productioncompanies.production_company_id, productioncompanies.production_company_name
from movies, productioncompanies
where production_company_name = "Pixar Animation Studios"
A possible solution is the following:
select count(*)
from movies join productioncompanies
on movies.production_company_id = productioncompanies.production_company_id
where production_company_name = 'Pixar Animation Studios';
%%sql
select count(*), p.production_company_name
from productioncompanymap as m
left join productioncompanies as p
on m.production_company_id = p.production_company_id
where production_company_name = 'Pixar Animation Studios'
I apologize for the vague detail to my question. I am still new to stack overflow so still finding my feet.
I have to link two databases of movies. The first database has a set of movie details (movie name, budget, rating, release date and reviews as well as a movie_id), the second table has a genre_id and genre's listing. I need to link the movie to the production comapny i.e. Monsters inc. to Pixar Animations, but the two databases does not have a primary key to link each other to. When I have the list of movies linked to the production company, I have to count the total movies per production company.
I hope this gives more detail, oh yeah, I am a student and this is one of my tests I have to do. I am unsure of how to join the tables and where.
I am asking myself how to best define a new database given two databases.
I have the following two databases
Author where I save information about authors i.e. Name, Birthyear, Country, Genre etc.
Book where I save information about the book i.e. AuthorName, ReleaseYear, Pages etc
How do I create a new database with the full information about all books and the author? I.e. a Book_Complete Database which includes Author.Name, ReleaseYear,Pages, Genre,ReleaseYear and Author.Birthyear, Author.Country?
Better to go for a single database and having 2 tables in it like
Author Table
AuthorId (PK)
Name
Birthyear
Country
Genre
Book Table
BookId (PK)
AuthorId (FK)
ReleaseYear
Pages
If you have two tables in a database you can combine them using JOIN. Here is SQLite tutorial on how to use JOIN.
https://www.sqlitetutorial.net/sqlite-join/
On the information you provided I assume you can you columns Name in table Author, and AuthorName in table Book. You can try something like this
SELECT
A.Name,
B.ReleaseYear,
B.Pages,
B.Genre,
B.ReleaseYear,
A.Birthyear,
A.Country
FROM
Author A
LEFT JOIN Book B
ON A.Name = B.AuthorName
Basically, I have these create these two tables on my app and want to store the combined version on a server. Or would you suggest another approach?
Yes we would. You should have one table per entity, i.e. one for the authors and one for the books. Thus you don't store data redundantly (e.g. the author's name or the book's title), which could otherwise lead to inconsistencies later. You can read up on database normalization here: https://en.wikipedia.org/wiki/Database_normalization or google it.
Now you must decide how to link the tables. One author can write multiple books. Can one book be written by multiple authors? Give both tables IDs you can work with (or find some natural unique key, like the ISBN for the book and maybe name + birth year for the author - the name only will probably not suffice and maybe it won't even when combined with the year).
If one book can only be written by one author, you have a 1:n relation (one book written by one author, one author writing multiple books).
author (author_id, name, birth_year, country, ...)
book (book_id, title, author_id, release_year, pages, ...)
If one book can have several authors, you have an m:n relation (one book written by multiple authors, one author writing multiple books).
author (author_id, name, birth_year, country, ...)
book (book_id, title, release_year, pages, ...)
book_author (book_id, author_id)
You can always join the tables, so as to get a combined result.
I have been trying to complete the following assignment:
Write a query that returns authors who've written books in more than one category and whose books are published by at least two different publishers. Display the author's Last Name and First Name, the Titles of Books they've written and the Book type. Sort the output by the author's last name.
These are the tables involved:
AUTHORS (Au_id, Au_lname, Au_fname, Phone, Address, City, State, Country, Postalcode)
PUBLISHERS (Pub_id, Pub_name, City, State)
TITLES (Title_id, Title, Type, Pub_id, Price, Advance, Total_sales, Notes, Pubdate, Contract)
TITLEAUTHOR (Au_id, Title_id)
I was able to identify the columns I need, but am not sure how to implement the filters (2 different authors, 2 different types). I assume I need to group by author id and count the Pub_id and Type columns.
This is what I have written so far:
SELECT AUTHORS.Au_lname, AUTHORS.Au_fname, TITLE.Title_id, TITLE.Type
from AUTHORS
JOIN TITLEAUTHOR ON AUTHORS.Au_id = TITLEAUTHOR.Au_id
JOIN TITLE ON TITLEAUTHOR.Title_i = TITLE.Title_i
group by AUTHORS.Au_lname, AUTHORS.Au_fname, TITLE.Title_id, TITLE.Type
ORDER BY AUTHORS.Au_lname;
Welcome to Stack Overflow, Tomasz! Congratulations on your first post. You've done a couple of excellent things already:
You included details on your schema
You included a clear problem statement
You included an example of the SQL you have already tried.
There are a couple of ways you could improve your post, which would help your chances of getting a good answer while also boosting your ability to participate in the community:
Be very careful with formatting - your second edit introduced some redundant text.
Be particular with your code - the first set you gave had some incorrect column names, which likely caused some users to look at your post and then ignore it. There's a critical window after you first post a question where it shows up near the top of the list; that's your best shot at getting answers, so it pays to be very careful with your presentation. Here's a link to some good reading on how to ask.
Be upfront about it when you're working on an assignment! As you can imagine, this community gets a lot of requests for help on homework. Many of the regular users get frustrated by people looking to 'cheat' on their assignments by posting their homework online. There are ways to get help, though: read this post over carefully so you're ready for your next question. The keys are to show that you've already tried to solve it yourself, be specific about what's not working, and be clear about the fact that this is homework.
Now, about your question! What you are looking for is the HAVING clause, which allows you to filter a query to return only those members of a group who meet a condition at the aggregate level. Your instinct about a COUNT was right on, and the HAVING clause will let you do that. Here's an example:
SELECT Au_id
FROM
AUTHORS
INNER JOIN
TITLEAUTHOR ON
AUTHORS.Au_id = TITLEAUTHOR.Au_id
INNER JOIN
TITLES ON
TITLEAUTHOR.Title_id = TITLE.Title_id
GROUP BY Au_id
HAVING
COUNT(DISTINCT TITLES.pub_id) > 1 AND
COUNT(DISTINCT TITLES.Type) > 1
Notice that this adds the word DISTINCT inside of the COUNT() function - this helps you meet the "two different publishers" requirement.
Once you understand how to use HAVING, then you can write a query to get the columns your assignment asked for, and filter the set to only return authors you want: the basic query structure is going to look like this:
SELECT MyColumns
FROM MyTables
WHERE Au_id IN
(
SELECT Au_id
FROM
AUTHORS
INNER JOIN
TITLEAUTHOR ON
AUTHORS.Au_id = TITLEAUTHOR.Au_id
INNER JOIN
TITLES ON
TITLEAUTHOR.Title_id = TITLE.Title_id
GROUP BY Au_id
HAVING
COUNT(DISTINCT TITLES.pub_id) > 1 AND
COUNT(DISTINCT TITLES.Type) > 1
)
ORDER BY WhateverYouWant
Good luck, and welcome to SQL!
I'm working on lab question that I just cannot come up with a solution, that would allow me to figure out the books that have more then one author(See the posted question below for my comments to make sense). My mind is totally blank on it. I'm very bad with word problems. I know that I have to do a JOIN statement which I've completed and I know that I have to use the COUNT function to count the number of authors but I honestly don't know how I would go about only counting the books that have 2 authors.
Any input would be appreciated. I tried to break it down into steps but it's just that one part that I'm not grasping in my mind.
Using the correct tables in your schema, create a query using either join operation you wish that will list the book title and number of authors for all books that have been written by more than one author. Give the title column an alias of "Book Title" and the column showing the number of authors an alias of "Number of Authors".
There is a BOOKS table and a AUTHOR table that are JOINED by a BOOK_AUTHOR table by their BOOKID in BOOKS and AUTHORID in AUTHOR.
I think I'm starting to understand that I have to use a mathematical equation to figure out more then one author. I don't understand the HAVING function all too well so I'm going to do more research on this one.
You were right, you need a JOIN, a COUNT, but also an HAVING to make sure there is more then one authors that written the book :
select title as 'Book Title', count(authors) as 'Number of Authors'
from books
join authors on books.id = authors.book_id
having count(authors) > 1
group by authors;
Make sure to adapt the table names and columns to the right one, as you didn't post them.
Note that if the books's author id column has the same name as the author id, you can use the USING keyword to join. then your query would become
select title as 'Book Title', count(authors) as 'Number of Authors'
from books
join authors on using(book_id)
having count(authors) > 1
group by authors;
Note that if you want to select only books that specifically have 2 authors you can change the having clause to having count(authors) = 2. But even if you ask for that in your question, according to the exercice you pasted, you did not understand properly the question.
I finally figured out the answer with all your help. Please see below:
SELECT DISTINCT Title "Book Title", COUNT(*)"Number of Authors"
FROM BOOKS JOIN
BOOK_AUTHOR ON
BOOKS.BookId = BOOK_AUTHOR.BookId
JOIN AUTHOR ON
BOOK_AUTHOR.AuthorId = Author.AuthorId
GROUP BY Title
HAVING COUNT(*) > 1;
So my tables I'm working with look like the following:
Book(BookID, Title)
Author(BookID, AuthID)
Writer(AuthID, PubID, FirstName, LastName)
Publisher(PubID, PubName, Country)
And I'd love to change them to make more sense, but I'm not allowed to even change their names at this point.
Anyway, I have two separate pieces of code that I want to run together. So it's the result of this:
select Book.Title
from Book
join Author
on Book.BookID=Author.BookID
group by Book.Title, Book.BookID
having count(*) >= 2
with this:
select AuthorID
from Author
join Publisher
on Author.PubID=Publisher.Publisher
where Publisher.Country like 'Australia'
Initially I thought INTERSECT might work but I quickly realised that because they're not matching fields, I need something else. And the fact that Writer and Publisher have to be linked via Author is throwing me off completely.
Is there a way to do this save going back to the table and changing it to something less unnecessarily complex?
I've been going through the list of statements and whatnot on trying to find a solution, but I'm not sure which one I'm supposed to be looking at. Perhaps something with GROUP in it? So anything, just a point in the right direction would be much appreciated.
Are you trying to find all books with more than one author published in Australia?
If so, the query would look something like this:
select b.Title
from Book b join
Author a
on b.BookID = a.BookID join
Writer w
on w.AuthId = a.AuthId join
Publisher p
on w.PubId = p.PubId
where p.Country like 'Australia'
group by b.Title, b.BookID
having count(*) >= 2;
I think there's a small conceptual misunderstanding blocking your way here.
The two queries can be combined into a single query, and return the results you want, via multiple joins involving all these tables.