Could any one please help me I have been working on a query containing unions n joins of multiple tables.. I have got the desired results but I want to get these results in some specific order so the whole result is being orderd according to one column.
Here is the snippet of code I am working on:
select name, age
from UserUni
order by age
union all
select age, Name
from UserOffice
order by age
Just add an ORDER BY clause at the very end of the UNION query, and it should be applied to the entire query:
select name, age
from UserUni
union all
select name, age
from UserOffice
order by age
Note that I swapped the order of the columns appearing in the second half of the UNION query because it doesn't make sense to put age and name into the same column. It is generally a requirement in a UNION query that the types and number of all columns be the same in boths halves of the query. One exception might be MySQL, which might appear to allow mixing numbers and text, but even in this case some implicit type conversion would be happening underneath the hood.
when we are using we can not use order by with both statements. because union at the end give one result end so how is it possible to use two order by statements.
you can check details here.
https://finalcodingtutorials.blogspot.ae/2017/03/order-by-clause-with-union-in-sql-server.html
hopefully it will resolve your issue will let you know complete details or union and order by statement.
Related
Actually I am building a Skype like tool wherein I have to show last 10 distinct users who have logged in my web application.
I have maintained a table in sql-server where there is one field called last_active_time. So, my requirement is to sort the table by last_active_time and show all the columns of last 10 distinct users.
There is another field called WWID which uniquely identifies a user.
I am able to find the distinct WWID but not able to select the all the columns of those rows.
I am using below query for finding the distinct wwid :
select distinct(wwid) from(select top 100 * from dbo.rvpvisitors where last_active_time!='' order by last_active_time DESC) as newView;
But how do I find those distinct rows. I want to show how much time they are away fromm web apps using the diff between curr time and last active time.
I am new to sql, may be the question is naive, but struggling to get it right.
If you are using proper data types for your columns you won't need a subquery to get that result, the following query should do the trick
SELECT TOP 10
[wwid]
,MAX([last_active_time]) AS [last_active_time]
FROM [dbo].[rvpvisitors]
WHERE
[last_active_time] != ''
GROUP BY
[wwid]
ORDER BY
[last_active_time] DESC
If the column [last_active_time] is of type varchar/nvarchar (which probably is the case since you check for empty strings in the WHERE statement) you might need to use CAST or CONVERT to treat it as an actual date, and be able to use function like MIN/MAX on it.
In general I would suggest you to use proper data types for your column, if you have dates or timestamps data use the "date" or "datetime2" data types
Edit:
The query aggregates the data based on the column [wwid], and for each returns the maximum [last_active_time].
The result is then sorted and filtered.
In order to add more columns "as-is" (without aggregating them) just add them in the SELECT and GROUP BY sections.
If you need more aggregated columns add them in the SELECT with the appropriate aggregation function (MIN/MAX/SUM/etc)
I suggest you have a look at GROUP BY on W3
To know more about the "execution order" of the instruction you can have a look here
You can solve problem like this by rank ordering the results by a key and finding the last x of those items, this removes duplicates while preserving the key order.
;
WITH RankOrdered AS
(
SELECT
*,
wwidRank = ROW_NUMBER() OVER (PARTITION BY wwid ORDER BY last_active_time DESC )
FROM
dbo.rvpvisitors
where
last_active_time!=''
)
SELECT TOP(10) * FROM RankOrdered WHERE wwidRank = 1
If my understanding is right, below query will give the desired output.
You can have conditions according to your need.
select top 10 distinct wwid from dbo.rvpvisitors order by last_active_time desc
Is it possible to do any sort of Union using SphinxQL? I want to return one set of results containing two queries and in order of the query. A simple example would be:
Select Author from idx_jobs where MATCH('#(Author) Steinbeck')
Union Select Author from idx_jobs where MATCH('#(Description) Steinbeck')
Naturally I could do
Select Author from idx_jobs where MATCH('#(Author, Description) Steinbeck')
but I'm trying to provide some control over 'relevance' in the results.
No union.
But seems like field weight would be useful
http://sphinxsearch.com/docs/current.html#sphinxql-select
.... OPTION field_weights=(author=1000)
Should put the matches against the author field first. (ie add that to end of second query)
Why are column ordinals legal for ORDER BY but not for GROUP BY? That is, can anyone tell me why this query
SELECT OrgUnitID, COUNT(*) FROM Employee AS e GROUP BY OrgUnitID
cannot be written as
SELECT OrgUnitID, COUNT(*) FROM Employee AS e GROUP BY 1
When it's perfectly legal to write a query like
SELECT OrgUnitID FROM Employee AS e ORDER BY 1
?
I'm really wondering if there's something subtle about the relational calculus, or something, that would prevent the grouping from working right.
The thing is, my example is pretty trivial. It's common that the column that I want to group by is actually a calculation, and having to repeat the exact same calculation in the GROUP BY is (a) annoying and (b) makes errors during maintenance much more likely. Here's a simple example:
SELECT DATEPART(YEAR,LastSeenOn), COUNT(*)
FROM Employee AS e
GROUP BY DATEPART(YEAR,LastSeenOn)
I would think that SQL's rule of normalize to only represent data once in the database ought to extend to code as well. I'd want to only right that calculation expression once (in the SELECT column list), and be able to refer to it by ordinal in the GROUP BY.
Clarification: I'm specifically working on SQL Server 2008, but I wonder about an overall answer nonetheless.
One of the reasons is because ORDER BY is the last thing that runs in a SQL Query, here is the order of operations
FROM clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
ORDER BY clause
so once you have the columns from the SELECT clause you can use ordinal positioning
EDIT, added this based on the comment
Take this for example
create table test (a int, b int)
insert test values(1,2)
go
The query below will parse without a problem, it won't run
select a as b, b as a
from test
order by 6
here is the error
Msg 108, Level 16, State 1, Line 3
The ORDER BY position number 6 is out of range of the number of items in the select list.
This also parses fine
select a as b, b as a
from test
group by 1
But it blows up with this error
Msg 164, Level 15, State 1, Line 3
Each GROUP BY expression must contain at least one column that is not an outer reference.
There is a lot of elementary inconsistencies in SQL, and use of scalars is one of them. For example, anyone might expect
select * from countries
order by 1
and
select * from countries
order by 1.00001
to be a similar queries (the difference between the two can be made infinitesimally small, after all), which are not.
I'm not sure if the standard specifies if it is valid, but I believe it is implementation-dependent. I just tried your first example with one SQL engine, and it worked fine.
use aliasses :
SELECT DATEPART(YEAR,LastSeenOn) as 'seen_year', COUNT(*) as 'count'
FROM Employee AS e
GROUP BY 'seen_year'
** EDIT **
if GROUP BY alias is not allowed for you, here's a solution / workaround:
SELECT seen_year
, COUNT(*) AS Total
FROM (
SELECT DATEPART(YEAR,LastSeenOn) as seen_year, *
FROM Employee AS e
) AS inline_view
GROUP
BY seen_year
databases that don't support this basically are choosing not to. understand the order of the processing of the various steps, but it is very easy (as many databases have shown) to parse the sql, understand it, and apply the translation for you. Where its really a pain is when a column is a long case statement. having to repeat that in the group by clause is super annoying. yes, you can do the nested query work around as someone demonstrated above, but at this point it is just lack of care about your users to not support group by column numbers.
I have a query in database like
SELECT 0 AS [DocumentType],'Select Document Type' [DocumentTypeX],0 ,0
UNION
SELECT dbo.tbDocumentType.*
FROM dbo.tbDocumentType where Site=#Site
It throws error message "All queries combined using a UNION, INTERSECT or EXCEPT operator must have an equal number of expressions in their target lists."
First and foremost rule for UNION Operation:
1.Both Query should have the same number of the resultset.
2.Respective Columns of both queries should have similar data types.
3.Never go with TableName.*.Instead Specify Column Names
Please check on that....
Instead of
SELECT dbo.tbDocumentType.*
Select the columns matching your UNION fields
SELECT dbo.tbDocumentType.[DocumentType],
dbo.tbDocumentType.[DocumentTypeX],
dbo.tbDocumentType.[Something1],
null -- Or use any value you want if doesnt have the column
I am working on an SQL query which should group by a column bidBroker and return all the columns in the table.
I tried it using the following query
select Product,
Term,
BidBroker,
BidVolume,
BidCP,
Bid,
Offer,
OfferCP,
OfferVolume,
OfferBroker,
ProductID,
TermID
from canadiancrudes
group by BidBroker
The above query threw me an error as follows
Column 'canadiancrudes.Product' is invalid in the select list because it is not contained in either an aggregate function or the
GROUP BY clause.
Is there any other way which returns all the data grouping by bidBroker without changing the order of data coming from CanadadianCrudes?
First if you are going to agregate, you should learn about agregate functions.
Then grouping becomes much more obvious.
I think you should explain what you are trying to accomplish here, because I suspect that you are trying to SORT bu Bidbroker, rather than grouping.
If you mean you want to sort by BidBroker, you can use:
SELECT Product,Term,BidBroker,BidVolume,BidCP,Bid,Offer,OfferCP,OfferVolume,OfferBroker,ProductID,TermID
FROM canadiancrudes
ORDER BY BidBroker
If you want to GROUP BY, and give example-data you can use:
SELECT c1.Product,c1.Term,c1.BidBroker,c1.BidVolume,c1.BidCP,c1.Bid,c1.Offer,c1.OfferCP,c1.OfferVolume,c1.OfferBroker,c1.ProductID,c1.TermID
FROM canadiancrudes c1
WHERE c1.YOURPRIMARYKEY IN (
select MIN(c2.YOURPRIMARYKEY) from canadiancrudes c2 group by c2.BidBroker
)
Replace YOURPRIMARYKEY with your column with your row-unique id.
As others have said, don't use "group by" if you don't want to aggregate something. If you do want to aggregate by one column but include others as well, consider researching "partition."