Is it possible to use a Count() or number from another Select query to SELECT TOP a number of rows in a different query?
Below is a sample of the update query I'm trying to use but would like to take the count from another query to replace "10".
...
WHERE Frames.Package IN (
SELECT TOP 10 Frames
FROM Frames.Package WHERE Package = "100"
ORDER BY Frames.ReferenceNumber
)
So for example, i've tried to do
SELECT TOP SelectQuery.RecordCount Frames
Sample SelectQuery.RecordCount
SELECT COUNT(Frames.Package) AS RecordCount
FROM Frames
HAVING Frames.Package = "100";
Any assistance would be appreciated...
Access does not support using a parameter for SELECT TOP. You must write a literal value into the text of the SQL statement.
From another answer: Select TOP N not working in MS Access with parameter
On that note, your two queries appear to be just interchanging HAVING and WHERE clauses to get the record count. It doesn't seem to be doing anything more, thus why bother with the TOP clause and simply SELECT * FROM Frames WHERE [..]?
Am I missing something?
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
As far as I am aware, the only way to get a random value in a SELECT statement is by using the newid() function, as the random() function doesn’t generate new values for each row.
This leads to the following awkward construction to get a random number from, say 0 - 9:
abs(checksum(newid())) % 10
If I use this expression in the SELECT clause, it behaves as expected. However, if I try something like the following:
select *
from table
where abs(checksum(newid())) % 10>4;
I should have though that I would get roughly half the rows. Instead I get I get all or none of them. Apparently newid() is only evaluated once, instead of for each row.
The question is, how can I use a random number in the WHERE clause?
More
There is a similar question which asks for fixed number of rows at random. In the above example I could have used:
select top 50 percent from table order by newid();
which will get me what I am looking for.
The question remains, how can I use a random number in the WHERE clause. For example, is it possible to do something like this?
select *
from table
where code={random number};
Here is one way to get around the problem
SELECT *
FROM (SELECT *,
Abs(Checksum(Newid())) % 10 AS ran
FROM yourtable) a
WHERE ran > 4;
for some reason newid() in where clause it is executed only once and it is checked with the constant.
When I check the execution plan your query is missing compute scalar where as my query has compute scalar present in execution plan.
The function newid() is calculate only once in the WHERE clause, not row by row. The trick is to force it to run row by row.
Of course it is possible to include it in a SELECT clause, and, in turn, include that in a CTE or a subquery, as per the other answers.
Microsoft offer a solution here: https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms189108(v=sql.105)?redirectedfrom=MSDN
The trick is to force newid() to recalculate by combining it with some row value. This is easily done in the checksum() function.
For example:
SELECT *
FROM table
WHERE abs(checksum(newid(),id)) % 10>4;
I should have though that I would get roughly half the rows. Instead I get I get all or none of them
You may get all of the rows or none of them ,since NEWID() is executed once per query when you use it in where clause..This is explained here by Conor Cunnigham and the technical term for this is called RumTimeConstants
You can look at your execution plan and look out for below expression
Const ConstValue
which you can see is calculated once and used throughout and finally you are doing just a boolean comparison,so you will end up with all rows or none
you have to use CTE Like the one stated in another answer or use Top with order by newid() or tablesample to return random rows
you may find Tablesample option more helpfull,since this may not go though all the table data to get only sample set of rows,unlike Newid()
below is one example on a table having 1000000 rows
select * from Orders
TABLESAMPLE (50 PERCENT)
plan
How can I LIMIT the result returned by a query in Adaptive Server IQ/12.5.0/0306?
The following gives me a generic error near LIMIT:
SELECT * FROM mytable LIMIT 10, 10;
Any idea why? This is my first time with this dbms
Sybase IQ uses row_count to limit the number of rows returned.
You will have to set the row count at the beginning of your statement and decide whether the statement should be TEMPORARY or not.
ROW_COUNT
SET options
LIMIT statement is not supported in Sybase IQ 12. I think there is not simple or clean solution, similarly like in old SQL server. But there are some approches that works for SQL server 2000 and should work also for Sybase IQ 12. I don't promise that queries below will work on copy&paste.
Subquery
SELECT TOP 10 *
FROM mytable
WHERE Id NOT IN (
SELECT TOP 10 Id FROM mytable ORDER BY OrderingColumn
)
ORDER BY OrderingColumn
Basically, it fetches 10 rows but also skips first 10 rows. To get this works, rows must be unique and ordering is important. Id cannot be more times in results. Otherwise you can filter out valid rows.
Asc-Desc
Another workaround depends on ordering. It uses ordering and fetches 10 rows for second page and you have to take care of last page (it does not work properly with simple formula page * rows per page).
SELECT *
FROM
(
SELECT TOP 10 *
FROM
(
SELECT TOP 20 * -- (page * rows per page)
FROM mytable
ORDER BY Id
) AS t1
ORDER BY Id DESC
) AS t2
ORDER BY Id ASC
I've found some info about non working subqueries in FROM statement in ASE 12. This approach maybe is not possible.
Basic iteration
In this scenario you can just iterate through rows. Let's assume id of tenth row is 15. Then it will select next 10 rows after tenth row. Bad things happen when you will order by another column than Id. It is not possible.
SELECT TOP 10 *
FROM mytable
WHERE Id > 15
ORDER BY Id
Here is article about another workarounds in SQL server 2000. Some should also works in similar ways in Sybase IQ 12.
http://www.codeproject.com/Articles/6936/Paging-of-Large-Resultsets-in-ASP-NET
All those things are workarounds. If you can try to migrate on newer version.
I will re-write my doubt to be more easy to understand.
I have one table named SeqNumbers that have only one column of data named PossibleNumbers, that has value from 1 to 10.000.
Then I have another Table named Terminals and one of the columns have the serial numbers of the terminals. What I want is get all the SerialNumbers that not exists in the Terminals table from 1 to 10.000.
I've created the SeqNumbers table only to do this... maybe there's another solution without using it... that's fine to me.
The query I have is:
SELECT PossibleNumbers from SeqNumbers
Where PossibleNumbers NOT IN (SELECT SerialNumbers from Terminals)**
Basically I want to list ALL serial numbers of terminals that doesn't exists in the database.
This Query works fine I think... but the problem is that I don't want all results in a single column.. I want these results displayed in 4 or 5 columns.
For my purpose I can only use the results from the query like that. I cannot use programmatically methods to do that.
Hope this is more clear now... Thanks for all the help...
select x, x+1000 from tablename
Will that do it for you?
If I'm reading this right, you'd probably have to do a self join; something like:
SELECT
LeftValues.ColA,
RightValues.ColA AS ColB
FROM YourTable LeftValues
LEFT JOIN YourTable RightValues ON LeftValues.ColA = RightValues.ColA - 1000
WHERE LeftValues.ColA < 1000
Note: Use the JOIN that makes sense for you (left if you are willing to accept NULLs in ColB, inner if you only want them where both values exist)
You can use a scripting language to parse the MySQL results to format it anyway you like. Are you using PHP to access the database? If so, let me know and I can cook one up for you.
I just saw your new updated question. In this case the order of the columns will be ordered by your SELECT statement and you can also sort too. Here is an example:
SELECT Column1, Column2 FROM my_table ORDER BY Column1, Column2 ASC
I have a sql statement that consists of multiple SELECT statements. I want to limit the total number of rows coming back to let's say 1000 rows. I thought that using the SET ROWCOUNT 1000 directive would do this...but it does not. For example:
SET ROWCOUNT 1000
select orderId from TableA
select name from TableB
My initial thought was that SET ROWCOUNT would apply to the entire batch, not the individual statements within it. The behavior I'm seeing is it will limit the first select to 1000 and then the second one to 1000 for a total of 2000 rows returned. Is there any way to have the 1000 limit applied to the batch as a whole?
Not in one statement. You're going to have to subtract ##ROWCOUNT from the total rows you want after each statement, and use a variable (say, "#RowsLeft") to store the remaining rows you want. You can then SELECT TOP #RowsLeft from each individual query...
And how would you ever see any records from the second query if the first always returns more than 1000 if you were able to do this in a batch?
If the queries are simliar enough you could try to do this through a union and use the rowcount on that as it would only be one query at that point. If the queries are differnt in the columns returned I'm not sure what you would get by limiting the entire group to 1000 rows because the meanings would be different. From a user perspective I'd rather consistently get 500 orders and 500 customer names than 998 orers and 2 names one day and 210 orders and 790 names the next. It would be impossible to use the application especially if you happened to be most interested in the information in the second query.
Use TOP not ROWCOUNT
http://msdn.microsoft.com/en-us/library/ms189463.aspx
You trying to get 1000 rows MAX from all tables right?
I think other methods may fill up with from the top queries first, and you may never get results from the lower ones.
The requirement sounds odd. Unless you are unioning or joining the data from the two selects, to consider them as one so that you apply a max rows simply does not make sense, since they are unrelated queries at that point. If you really need to do this, try:
select top 1000 from (
select orderId, null as name, 'TableA' as Source from TableA
union all
select null as orderID, name, 'TableB' as Source from TableB
) a order by Source
SET ROWCOUNT applies to each individual query. In your given example, it's applied twice, once to each SELECT statement, since each statement is its own batch (they're not grouped or unioned or anything, and so execute completely separately).
#RedFilter's approach seems the most likely to give you what you want.
Untested and doesn't make use of ROWCOUNT, but could give you an idea?
Assumes col1 in TableA and TableB are the same type.
SELECT TOP 1000 *
FROM (select orderId
from TableA
UNION ALL
select name from TableB) t
The following worked for me:
CREATE PROCEDURE selectTopN
(
#numberOfRecords int
)
AS
SELECT TOP (#numberOfRecords) * FROM Customers
GO
this is your solution :
TOP (Transact-SQL)
and about ##RowCount you can read this Link :
SET ROWCOUNT (Transact-SQL)
Important
Using SET ROWCOUNT will not affect DELETE, INSERT, and UPDATE statements in a future release of SQL Server. Avoid using SET ROWCOUNT with DELETE, INSERT, and UPDATE statements in new development work, and plan to modify applications that currently use it. For a similar behavior, use the TOP syntax. For more information, see TOP (Transact-SQL).
I think two way will work.!