Can you help me please with the divide select in SQL? I use the Oracle Apex Express Edition. I have three tables. In English (original names are in brackets): User (Uzivatel), Event (Udalost) and Groups of users (Skupina_u). Their context is on screens:
Now I have to use divide select in SQL. This select is formulated: You must show all users who were on all events. In my tables, you can see that I have two users, who were on all events. They are part of group “SK2.” I am using this select:
select *
from Uzivatel
where not exists (select *
from Skupina_u
where not exists (select *
from Udalost
where Skupina_u.ID_uz = Uzivatel.ID_uz
and Skupina_u.ID_uz = Udalost.ID_uz))
But the result is: no data found.
Thank you for help.
This is answering the question you pose in English . . . "Find all users who are on all events."
This is an example of a set-within-sets query. I think the best approach is using aggregation (because the same structure can be used for many questions). Let me show you using the English names for the tables and columns:
select eu.UserId
from User_Events eu
group by eu.UserId
having count(distinct eu.EventId) = (select count(*) from Events e)
That is, select all the users where the number of distinct event ids is the number in the events table. If you only want events that have users, then use the following having clause:
having count(distinct eu.EventId) = select count(distinct eventId) from Events e)
Related
From the code as shown below. I wonder that why it can select data from 2 tables in same time that are table "venue AS v" and table "as s".
or I misunderstand?
SELECT name, s.num_match
FROM venue AS v,
(SELECT venue_id, COUNT(*) AS num_match
FROM match
GROUP BY venue_id) AS s
WHERE v.venue_id = s.venue_id
LIMIT 3;
Yes you can using JOIN clause for example.
More infos here: https://www.informit.com/articles/article.aspx?p=30875&seqNum=5
Yes you can select data from as many as tables you want at the same time.
In this case you are trying to get an aggregated number from table-s and join it with the table v.
There are many ways to write the code to join the table. Above is one method which you have used.
I work in recruiting and would like to get a list of jobs that are posted to multiple offices along with the names of those offices per job.
I started with the query below to identify the jobs with multiple offices. What is my next step for showing offices.name for only jobs with multiple offices? Bonus if I can get one record per job and have the office names fill into columns. I'm using SQL Workbench connected to Amazon Redshift. Thanks much!
select jobs_offices.job_id, count(offices.id)
from jobs_offices join offices on jobs_offices.office_id = offices.id
group by jobs_offices.job_id
having count(offices.id) >1
order by count(offices.id) DESC
Your query looks good so far, it is just missing the office name? I believe you could get a comma-separated list of the offices by adding the listagg function. Something like select jobs_offices.job_id, listagg(offices.name, ', ') from ...
Redshift docs
you can use corelated subquery
select t.* from offices t
where exists ( select 1 from jobs_offices t1 where t1.office_id=t.id
group by t1.job_id
having count(*) >1
)
I am trying to display several columns with different counts in a microsoft access query. It doesn't let me do certain things a normal query can b/c it has the sql design view.
I'd like to display
multiple single etc columns with their counts.
Note: the table names and attributes have been changed.
select (select count(*)as multiple from (select userId from dbo.Purchases
where userId is not null GRoup by userId having count(*)>1) x), (
select count(*)as single from (select userId from dbo.Purchases where
userId is not null GRoup by userId having count(*)=1) x );
if I do these separately I can display it, but I'd like to combine them into one query and one row. Is this possible?
select count(*)as multiple from (select userId from dbo.Purchases
where userId is not null GRoup by userId having count(*)>1) x)
It's very easy with 2 queries:
First one, saved as "Purchases Summary"
Select UserID, count(UserID) as Count from Purchases Group By UserID
With a 2nd built on it:
SELECT Sum(IIf([count]=1,1)) AS [Single], Sum(IIf([count]>1,1)) AS Multiple FROM [Purchases Summary]
I cannot find a clever way to combine this into a single query.
I don't know what my problem last night was, but the single query is
SELECT Sum(IIf([count]=1,1)) AS [Single], Sum(IIf([count]>1,1)) AS Multiple
FROM (Select UserID, count(UserID) as Count from Purchases Group By UserID)
Don George solution also would work.
I ended up using a form and VBA for each column. An issue I had was that I needed to use a distinct call for unique IDs and when there is a sql design view that's not really supported. distinctrow is supported, but it would not work for my query. I ended up writing it as before so that it did not need distinct.
This is the VBA I used to override each input inside of an access form. The currentDb needs to be connected to the database properly before it will also work.
selectStatement = "SELECT Count(* ) FROM (SELECT userID FROM dbo_Purchases WHERE userID is not null GROUP BY userID HAVING count(*)>1) AS x;"
rs = CurrentDb.OpenRecordset(selectStatement).Fields(0).Value
[Text30].Value = rs
I need to write a sql query that will find users that have at least 2 different books from set of (book1, book2 and book3) . what technique can be used to write such a query?
I want to find all users who own at least 2 books from a specified set of books ('book_1','book_2','book_3') but do not own any of the books in a second specified set ('book_4')?
EDIT:
OP couldn't explain what he is actually looking for. What OP actually trying to do is:
Find all users who own at least 2 different books and exclude those users who has a book called 'book_4'.
Try this:
SELECT Users,Count(DISTINCT Books) as CountOfBooks
FROM TableName
GROUP BY Users
HAVING COUNT(DISTINCT Books) >= 2
Explanation:
Here, we are grouping the table contents with users field and counting the number of distinct books that each user has. The HAVING clause is helpful to filter the result with the count of distinct book.
You can change the number 2 with the count you need. And = can be used for exact match instead of atleast.
See an example in SQL Fiddle.
EDIT:
For excluding users with book_4, try this:
SELECT Users,Count(DISTINCT Books) as CountOfBooks
FROM TableName
WHERE Users NOT IN (SELECT Users FROM TableName WHERE Books = 'book_4')
GROUP BY Users
HAVING COUNT(DISTINCT Books) >= 2
OR a faster version (without using IN):
SELECT T1.Users,Count(DISTINCT T1.Books) as CountOfBooks
FROM TableName T1 LEFT JOIN
(SELECT Users
FROM TableName
WHERE Books = 'Book4') T2 ON T2.Users=T1.Users
WHERE T2.Users IS NULL
GROUP BY T1.Users
HAVING COUNT(DISTINCT T1.Books)>=2
An example in SQL Fiddle.
Try this,
select USERS,count(distinct BOOKS) from myTable
where BOOKS in('Book1','Book2','Book3')
group by USERS
having count(distinct BOOKS) >=2
I had this sql statement running for these two tables: tblStations and tblThreads, for counting number of Stations in each thread:
SELECT tblThreads.*, (SELECT COUNT(*) FROM tblStations WHERE tblStations .fldThreadID=tblThreads.fldID) AS TotalStationsInThread FROM tblThreads;
and then display tblThread.Name and TotalStationsInThread, for each thread in the system.
Now I added another table (tblUsers) in this hierarchy:
each thread can have many users, and each user can have many stations.
The three tables are related to each other by this:
tblStations.fldUserID=tblUsers.fldID > tblUsers.fldThreadID=tblThreads.fldID.
So I changed my SQL query to this:
SELECT tblThreads.*, (SELECT COUNT(*) FROM tblStations WHERE tblStations.fldUserID=tblUsers.fldID AND tblUsers.fldThreadID=tblThreads.fldID) AS TotalStationsInThread FROM tblThreads;
But now I'm getting this message: "No value given for one or more required parameters." It's like the database can't connect the tables tblStations with tblThreads via tblUsers...
Any help please on how to count the number of stations that are connected to all the users that are connected to each thread??
This is the correct answer for MS Access Jet Database Engine:
SELECT tblThreads.*, (SELECT COUNT(tblStations.fldUserID) FROM tblStations INNER JOIN tblUsers ON tblStations.fldUserID = tblUsers.fldID WHERE tblUsers.fldThreadID = tblThreads.fldID) AS TotalStationsInThread FROM tblThreads;
Many thanks for Gordon Linoff for his answer.
You need to include tblUsers in the from clause:
SELECT tblThreads.*,
(SELECT COUNT(*)
FROM tblUsers inner join
tblStations
on tblStations.fldUserID = tblUsers.fldID
WHERE tblUsers.fldThreadID = tblThreads.fldID
) AS TotalStationsInThread
FROM tblThreads;