I've got two SQL Server tables authors, and articles where authors primary key (AuthorID) is a foreign key in the articles table to represent a simple one-to-many relationship between authors and articles table. Now here's the problem, I need to issue a full text search on the authors table based on the first name, last name, and biography columns. The full text search is working awesome and ranking and all. Now I need to add one more criteria to my search, I need all the non-articles contributors to be ignored from the search. To achieve that I chose to create a view with all the contributors that have articles and search against this view. So I created the view this way:
Create View vw_Contributors_With_Articles
AS
Select * from Authors
Where Authors.ContributorID
IN ( Select Distinct (Articles.ContributorId) From Articles)
It's working but I really don't like the subquery thing. The join gets me all the redundant authorIDs, tried distinct but didn't work with the biography column as it's type is ntext. Group by wouldn't do it for me because I need all the columns not any aggregate of them.
What do you think guys? How can I improve this?
An EXISTS allows for the potential duplicate entries when there are multiple articles per author:
Select * from Authors
Where EXISTS (SELECT *
FROM Articles
WHERE Articles.ContributorId = Authors.ContributorId)
Edit:
To clarify, you can not DISTINCT on ntext columns. So, you can not have a JOIN solution, unless you use a derived table on articles in the JOIN and avoid using articles directly. Or you convert the ntext to nvarchar(max).
EXISTS or IN is your only option.
Edit 2:
...unless you really want to use a JOIN and you have SQL Server 2005 or higher, you can CAST and DISTINCT (aggregate) to avoid multiple rows in the output...
select DISTINCT
Authors.ContributorID,
Authors.AnotherColumn,
CAST(Authors.biography AS nvarchar(max)) AS biography,
Authors.YetAnotherColumn,
...
from
Authors
inner join
Articles on
Articles.ContributorID = Authors.ContributorID
You want an inner join
select
*
from
Authors
inner join
Articles on
Articles.ContributorID = Authors.ContributorID
This will return only authors who have a an entry on the Articles table, matched by ContributorID.
Select the distinct contributorIDs from the Articles table to get the individual authors who have written an article, and join the Authors table to that query - so something like
select distinct Articles.contributorID, Authors.*
from Articles
join Authors on Articles.contributerID = Authors.ContributerId
Related
We have to select authors that havent written a book but there are 3 different tables which makes me confused about how to write the join expression.
We have tables:
authors: author_id
authorships: author_id, book_id
books: book_id.
Obviously I selected the names from authors and tried inner join but it wont work for me. Help would be appreciated!
Since this sounds like a school assignment I won't give the full answer.
Try using an outer join between authors and authorship. Make sure you retrieve the book I'd from the authorship.
Try to work out what an author who has not published looks like the. You can use this to formulate the query for the answer you are looking for with an appropriate where clause.
This is a good spot to use the LEFT JOIN antipattern:
SELECT a.*
FROM authors a
LEFT JOIN authorships s ON s.author_id = a.author_id
WHERE s.author_id IS NULL
Rationale: when the LEFT JOIN comes up empty, it means that the author has no corresponding record in the authorships table. The WHERE clause filters out on unmatched authors records only (ie authors that have no books). This is called an antipattern because the purpose of a JOIN is usually to match records, whereas here we use it to detect unmatched records.
Its really easy, just check which column seems to be having common value between all this three tables if something is common atleast within two tables then put inner join on those two and an outer join on the uncommon data table.
Remember your Aliases will always matter when you join between different tables, also the ON and WHERE should be properly mentioned.
I'm trying to figure out how to query against a composite key.
In my select result, I want the book name, author, category, and selling price. So far I have select title,category,price from books1 where books1.category='MYS';
but I'm not sure how to go about getting the author name.
I'm not sure why you have books1 when the model show the table named books. Books is a horrible name for a table -- typically in relational databases you use the singular -- eg book.
Here is how you do a join:
Select a.First, a.Last
from books b
join books_authors ab on b.b_code = ab.book_code
join authors a on ab.authorId = a.id
where b.category = 'MYS'
also all of your field names have spaces in them -- I don't know what platform you are using so I've no idea how to escape the names. Using spaces in field name is non-standard and not acually SQL. I'd advise against it whenever possible.
I'm creating an archive for Academic Papers. Each paper may have one author, or multiple authors. I've created the tables in the following manner:
Table 1: PaperInfo - Each row contains information on the paper
Table 2: PaperAuthor - Only Two Columns: contains PaperID, and AuthorID
Table 3: AuthorList - Contains Author Information.
There is also a Table 4 which is linked to Table 4, which contains a list of Universities which the author belongs to, but I'm going to leave it out for now in case it gets too complicated.
I wish to have a Query which will link all three tables together, and display Paper Information of the recordset in a table, with columns such as these:
Paper Title
Paper Authors
The column "Paper Authors" is going to contain more than one authors in some cases.
I've wrote the following query:
SELECT a.*,b.*,c.*
FROM PaperInfo a, PaperAuthor b, AuthorList c
WHERE a.PaperID = b.PaperID AND b.AuthorID = c.AuthorID
So far, the results I've been getting for each row is one author per row. I wish to contain more authors in one column. Can this be done in anyway?
Note: I'm using Access 2010 as my database.
In straight SQL the answer unfortunately is that it isn't possible. You would need to use a processing language in order to get the result you are after.
Since you mention you are using Access 2010 please refer to this question: is there a group_concat function in ms-access?
Particularly, read the post which points to http://www.rogersaccesslibrary.com/forum/generic-function-to-concatenate-child-records_topic16&SID=453fabc6-b3z9-34z6zb14-a78f832z-19z89a2c.html
You probably need to implement a custom function but the 2nd url does what you are looking for.
This functionality is not part of the SQL standard, but different vendors have solutions for it, see for instance Pivot Table with many to many table, MySQL pivot table.
If you know the maximum number of authors per paper (for example 3 or 4), you could get away with a triple or quadruple left join.
What you are after is an inner join.
An SQL JOIN clause is used to combine rows from two or more tables, based on a common field between them.
The most common type of join is: SQL INNER JOIN (simple join). An SQL INNER JOIN return all rows from multiple tables where the join
condition is met.
http://www.w3schools.com/sql/sql_join.asp
You may want to combine the inner join with a group to give you 1 paper to many authors in your results.
The GROUP BY statement is used in conjunction with the aggregate
functions to group the result-set by one or more columns.
http://www.w3schools.com/sql/sql_groupby.asp
I know the title is confusing but its the best I could explain it. Basically im developing a cinema listings website for a company which owns two cinemas. So I have a database which has the two tables "Films" and "Listings" with data for both cinemas in them.
I'm trying to select all films and their data for one cinema if the films name shows up in the listings (since the two cinemas share all films but in the table but the may not have the same films showing)
Here is what i have come up with but I run into a problem as when the "SELECT DISTINCT" returns more than one result it obviously cant be matched with the FilmName on tbl Films.
How can i check this value for all FilmNames on tblFilms?
SELECT *
FROM tblFilms
WHERE FilmName = (SELECT DISTINCT FilmName FROM tblListings WHERE Cimema = 1)
use IN if the subquery return multiple values,
SELECT *
FROM tblFILMS
WHERE FilmName IN (SELECT DISTINCT FilmName FROM tblListings WHERE Cimema = 1)
Another way to solve thius is by using JOIN (which I recommend)
SELECT DISTINCT a.*
FROM tblFILMS a
INNER JOIN tblListings b
ON a.FilmName = b.FilmName AND
b.Cimema = 1
for faster query execution, add an INDEX on FilmName on both tables.
If you have your schemas for the tables, that would help.
That said, I believe what you want to look at is the JOIN keyword. (inner/outer/left/etc). That's exactly what JOIN is meant to do (ie your title).
I have 3 tables (archive has many sections, section (may) belong to many archives):
archive
id PK
description
archive_to_section
archive_id PK FK
section_id PK FK
section
id PK
description
What would the SQL look like to list all the sections that belong a certain archive id?
I am just learning SQL. From what I've read it sounds like I would need a join, or union? FYI I'm using postgres.
[Edit] This is the answer from gdean2323 written without aliases:
SELECT section.*
FROM section
INNER JOIN archive_to_section
ON section.id = archive_to_section.section_id
WHERE archive_to_section.archive_id = $this_archive_id
SELECT s.*
FROM section s INNER JOIN archive_to_section ats ON s.id = ats.section_id
WHERE ats.archive_id = 1
SELECT s.*
FROM archive_to_section ats
INNER JOIN section s ON s.id=ats.section_id
WHERE ats.archive_id= #archiveID