I'm looking to some expresion like this (using SQL Server 2008)
SELECT TOP 10 columName FROM tableName
But instead of that I need the values between 10 and 20. And I wonder if there is a way of doing it using only one SELECT statement.
For example this is useless:
SELECT columName FROM
(SELECT ROW_NUMBER() OVER(ORDER BY someId) AS RowNum, * FROM tableName) AS alias
WHERE RowNum BETWEEN 10 AND 20
Because the select inside brackets is already returning all the results, and I'm looking to avoid that, due to performance.
Use SQL Server 2012 to fetch/skip!
SELECT SalesOrderID, SalesOrderDetailID, ProductID, OrderQty, UnitPrice, LineTotal
FROM AdventureWorks2012.Sales.SalesOrderDetail
OFFSET 10 ROWS FETCH NEXT 10 ROWS ONLY;
There's nothing better than you're describing for older versions of sql server. Maybe use CTE, but unlikely to make a difference.
WITH NumberedMyTable AS
(
SELECT
Id,
Value,
ROW_NUMBER() OVER (ORDER BY Id) AS RowNumber
FROM
MyTable
)
SELECT
Id,
Value
FROM
NumberedMyTable
WHERE
RowNumber BETWEEN #From AND #To
or, you can remove top 10 rows and then get next 10 rows, but I double anyone would want to do that.
There is a trick with row_number that does not involve sorting all the rows.
Try this:
SELECT columName
FROM (SELECT ROW_NUMBER() OVER(ORDER BY (select NULL as noorder)) AS RowNum, *
FROM tableName
) as alias
WHERE RowNum BETWEEN 10 AND 20
You cannot use a constant in the order by. However, you can use an expression that evaluates to a constant. SQL Server recognizes this and just returns the rows as encountered, properly enumerated.
Why do you think SQL Server would evaluate the entire inner query? Assuming your sort column is indexed, it'll just read the first 20 values. If you're really nervous you could do this:
Select
Id
From (
Select Top 20 -- note top 20
Row_Number() Over(Order By Id) As RowNum,
Id
From
dbo.Test
Order By
Id
) As alias
Where
RowNum Between 10 And 20
Order By
Id
but I'm pretty sure the query plan is the same either way.
(Really) Fixed as per Aaron's comment.
http://sqlfiddle.com/#!3/db162/6
One more option
SELECT TOP(11) columName
FROM dbo.tableName
ORDER BY
CASE WHEN ROW_NUMBER() OVER (ORDER BY someId) BETWEEN 10 AND 20
THEN ROW_NUMBER() OVER (ORDER BY someId) ELSE NULL END DESC
You could create a temp table that is ordered the way you want like:
SELECT ROW_NUMBER() OVER(ORDER BY someId) AS RowNum, * FROM tableName
into ##tempTable
...
That way you have an ordered list of rows.
and can just query by row number the subsequent times instead of doing the inner query multiple times.
Related
I am trying to select rows 3 - 5 of:
SELECT *
FROM Finance_User
ORDER BY email DESC
I originally had just:
SELECT
ROW_NUMBER() OVER (ORDER BY email DESC) AS RowNum, *
FROM
Finance_User
WHERE
RowNum BETWEEN 3 AND 5
But this did not work as RowNum was an invalid column.
Instead I did the below:
WITH OrderedUsers AS
(
SELECT
ROW_NUMBER() OVER (ORDER BY email DESC) AS RowNum, *
FROM
Finance_User
)
SELECT *
FROM OrderedUsers
WHERE RowNum BETWEEN 3 AND 5
This works perfectly fine. However, I am concerned that there might be performance issues with this as it seems to be selecting from the table twice?
ROW_NUMBER() with a CTE (or a subquery) won't scan the table twice. However using the window function might incur additional processing for the RDBMS.
You could achieve the same results with ORDER BY ... OFFSET ... FETCH ..., available starting SQL-Server 2012, that are provided specifically for the purpose of paging a resultset:
SELECT *
FROM Finance_User
ORDER BY email DESC
OFFSET 2 ROWS FETCH NEXT 3 ROWS ONLY
From the documentation:
We recommend that you use the OFFSET and FETCH clauses instead of the TOP clause to implement a query paging solution and limit the number of rows sent to a client application.
Your query is fine.
WITH AS clause is a Common Table Expression which means that this query may be reused later and should be cached if needed and possible. So there should not be any problem with "selecting from the table twice".
The same result you can get with this query:
SELECT * from
(SELECT ROW_NUMBER() OVER (ORDER BY email DESC) AS RowNum, * FROM Finance_User)
where RowNum between 3 and 5
And finally, you can always check execution plan and make sure of it as well.
In my SP I have the following:
with Paging(RowNo, ID, Name, TotalOccurrences) as
(
ROW_NUMBER() over (order by TotalOccurrences desc) as RowNo, V.ID, V.Name, R.TotalOccurrences FROM dbo.Videos V INNER JOIN ....
)
SELECT * FROM Paging WHERE RowNo BETWEEN 1 and 50
SELECT COUNT(*) FROM Paging
The result is that I get the error: invalid object name 'Paging'.
Can I query again the Paging table? I don't want to include the count for all results as a new column ... I would prefer to return as another data set. Is that possible?
Thanks, Radu
After more research I fond another way of doing this:
with Paging(RowNo, ID, Name, TotalOccurrences) AS
(
ROW_NUMBER() over (order by TotalOccurrences desc) as RowNo, V.ID, V.Name, R.TotalOccurrences FROM dbo.Videos V INNER JOIN ....
)
select RowNo, ID, Name, TotalOccurrences, (select COUNT(*) from Paging) as TotalResults from Paging where RowNo between (#PageNumber - 1 )* #PageSize + 1 and #PageNumber * #PageSize;
I think that this has better performance than calling two times the query.
You can't do that because the CTE you are defining will only be available to the FIRST query that appears after it's been defined. So when you run the COUNT(*) query, the CTE is no longer available to reference. That's just a limitation of CTEs.
So to do the COUNT as a separate step, you'd need to not use the CTE and instead use the full query to COUNT on.
Or, you could wrap the CTE up in an inline table valued function and use that instead, to save repeating the main query, something like this:
CREATE FUNCTION dbo.ufnExample()
RETURNS TABLE
AS
RETURN
(
with Paging(RowNo, ID, Name, TotalOccurrences) as
(
ROW_NUMBER() over (order by TotalOccurrences desc) as RowNo, V.ID, V.Name, R.TotalOccurrences FROM dbo.Videos V INNER JOIN ....
)
SELECT * FROM Paging
)
SELECT * FROM dbo.ufnExample() x WHERE RowNo BETWEEN 1 AND 50
SELECT COUNT(*) FROM dbo.ufnExample() x
Please be aware that Radu D's solution's query plan shows double hits to those tables. It is doing two executions under the covers. However, this still may be the best way as I haven't found a truly scalable 1-query design.
A less scalable 1-query design is to dump a completed ordered list into a #tablevariable , SELECT ##ROWCOUNT to get the full count, and select from #tablevariable where row number between X and Y. This works well for <10000 rows, but with results in the millions of rows, populating that #tablevariable gets expensive.
A hybrid approach is to populate this temp/variable up to 10000 rows. If not all 10000 rows are filled up, you're set. If 10000 rows are filled up, you'll need to rerun the search to get the full count. This works well if most of your queries return well under 10000 rows. The 10000 limit is a rough approximation, you can play around with this threshold for your case.
Write "AS" after the CTE table name Paging as below:
with Paging AS (RowNo, ID, Name, TotalOccurrences) as
(
ROW_NUMBER() over (order by TotalOccurrences desc) as RowNo, V.ID, V.Name, R.TotalOccurrences FROM dbo.Videos V INNER JOIN ....
)
SELECT * FROM Paging WHERE RowNo BETWEEN 1 and 50
SELECT COUNT(*) FROM Paging
I have an SQL Query that i'm running but I only want to select a specific row. For example lets say my query was:
Select * from Comments
Lets say this returns 10 rows, I only want to select the 8th record returned by this query. I know I can do:
Select Top 5 * from Comments
To get the top 5 records of that query but I only want to select a certain record, is there anything I can put into this query to do that (similar to top).
Thanks
jack
This is a classic interview question.
In Ms SQL 2005+ you can use the ROW_NUMBER() keyword and have the Predicate ROW_NUMBER = n
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber = 5;
In SQL2000 you could do something like
SELECT Top 1 *FROM
[tblApplications]
where [ApplicationID] In
(
SELECT TOP 5 [ApplicationID]
FROM [dbo].[tblApplications]
order by applicationId Desc
)
How about
SELECT TOP 1 * FROM
(SELECT TOP 8 * FROM Comments ORDER BY foo ASC)
ORDER BY foo DESC
First, you should say which RDBMS you're using.
Second, you should give careful thought to what it is you're trying to accomplish. Relational Databases are set-based. In general, the order of elements in a set does not matter. You'll want to ask why it matters in this case, then see if there's a better way to embed the concept of order into the query itself.
For instance, in SQL Server 2005 (and other RDBMS), you can use the ROW_NUMBER function to assign a sequential number to each row returned, based on the criteria you specify. You could then select rows based on the row number. Example from Books Online:
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 50 AND 60;
SELECT * FROM comments WHERE ...conditions... LIMIT 1 OFFSET 8
OFFSET is a good thing for MySQL
For SQL Server 2005:
select rank() OVER (ORDER BY c.subject, c.date) as rank, c.subject, c.date
from comments c
where rank = 8
Well, in T-SQL (the dialect for SQL Server) you can do the following:
SELECT TOP 1 *
FROM (SELECT TOP 8 *
FROM Table
ORDER
BY SortField)
ORDER
BY SortField DESC
This way you get the 8th record.
I have read the question & your comments on you would want next 3 blog comments etc.
How is your tables structured?
Assume that you have blog post Id & comment Id is generated in ascending order for each blog post, you could do a SELECT based on the current Id.
e.g. if the blogpostId = 101, you get the top 3 comments order by posted Id. Now lets say, you want to get the next 3 comments - you could do a SELECT WHERE commentId between the last comment id shown TO the comment id - 3
But all that depends on how your tables are defined.
In SQL 2000 where you do not have ROW_NUMBER() function you could use a work-around like this:
SELECT CommentsTableFieldList, IDENTITY(INT, 1,1) as seqNo
INTO #SeqComments
FROM Comments
SELECT * FROM #SeqComments
WHERE seqNo = 8
select top 1 *
from TableName
where ColumnName1 in
(
select top nth ColumnName1
from TableName
order by ColumnName1 desc
)
order by ColumnName1 desc
From the SELECT reference, use the LIMIT keyword:
SELECT * FROM tbl LIMIT 5,10; # Retrieve rows 6-15
SELECT * FROM tbl LIMIT 5; # Retrieve first 5 rows
Note: this is for MySQL, other SQL engines may have a different keyword.
Select from tablename limit nthrow,1;
try This
Let us assume , We want select 5th row of WC_Video Table
And
Select * from (Select Row_Number() over (Order by Uploadedon) as 'rownumber',* from Wc_Video )as Temp where rownumber=5
I want to use the ROW_NUMBER() to get...
To get the max(ROW_NUMBER()) --> Or i guess this would also be the count of all rows
I tried doing:
SELECT max(ROW_NUMBER() OVER(ORDER BY UserId)) FROM Users
but it didn't seem to work...
To get ROW_NUMBER() using a given piece of information, ie. if I have a name and I want to know what row the name came from.
I assume it would be something similar to what I tried for #1
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
but this didn't work either...
Any Ideas?
For the first question, why not just use?
SELECT COUNT(*) FROM myTable
to get the count.
And for the second question, the primary key of the row is what should be used to identify a particular row. Don't try and use the row number for that.
If you returned Row_Number() in your main query,
SELECT ROW_NUMBER() OVER (Order by Id) AS RowNumber, Field1, Field2, Field3
FROM User
Then when you want to go 5 rows back then you can take the current row number and use the following query to determine the row with currentrow -5
SELECT us.Id
FROM (SELECT ROW_NUMBER() OVER (ORDER BY id) AS Row, Id
FROM User ) us
WHERE Row = CurrentRow - 5
Though I agree with others that you could use count() to get the total number of rows, here is how you can use the row_count():
To get the total no of rows:
with temp as (
select row_number() over (order by id) as rownum
from table_name
)
select max(rownum) from temp
To get the row numbers where name is Matt:
with temp as (
select name, row_number() over (order by id) as rownum
from table_name
)
select rownum from temp where name like 'Matt'
You can further use min(rownum) or max(rownum) to get the first or last row for Matt respectively.
These were very simple implementations of row_number(). You can use it for more complex grouping. Check out my response on Advanced grouping without using a sub query
If you need to return the table's total row count, you can use an alternative way to the SELECT COUNT(*) statement.
Because SELECT COUNT(*) makes a full table scan to return the row count, it can take very long time for a large table. You can use the sysindexes system table instead in this case. There is a ROWS column that contains the total row count for each table in your database. You can use the following select statement:
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('table_name') AND indid < 2
This will drastically reduce the time your query takes.
You can use this for get first record where has clause
SELECT TOP(1) * , ROW_NUMBER() OVER(ORDER BY UserId) AS rownum
FROM Users
WHERE UserName = 'Joe'
ORDER BY rownum ASC
ROW_NUMBER() returns a unique number for each row starting with 1. You can easily use this by simply writing:
ROW_NUMBER() OVER (ORDER BY 'Column_Name' DESC) as ROW_NUMBER
May not be related to the question here. But I found it could be useful when using ROW_NUMBER -
SELECT *,
ROW_NUMBER() OVER (ORDER BY (SELECT 100)) AS Any_ID
FROM #Any_Table
select
Ml.Hid,
ml.blockid,
row_number() over (partition by ml.blockid order by Ml.Hid desc) as rownumber,
H.HNAME
from MIT_LeadBechmarkHamletwise ML
join [MT.HAMLE] h on ML.Hid=h.HID
SELECT num, UserName FROM
(SELECT UserName, ROW_NUMBER() OVER(ORDER BY UserId) AS num
From Users) AS numbered
WHERE UserName='Joe'
You can use Row_Number for limit query result.
Example:
SELECT * FROM (
select row_number() OVER (order by createtime desc) AS ROWINDEX,*
from TABLENAME ) TB
WHERE TB.ROWINDEX between 0 and 10
--
With above query, I will get PAGE 1 of results from TABLENAME.
If you absolutely want to use ROW_NUMBER for this (instead of count(*)) you can always use:
SELECT TOP 1 ROW_NUMBER() OVER (ORDER BY Id)
FROM USERS
ORDER BY ROW_NUMBER() OVER (ORDER BY Id) DESC
Need to create virtual table by using WITH table AS, which is mention in given Query.
By using this virtual table, you can perform CRUD operation w.r.t row_number.
QUERY:
WITH table AS
-
(SELECT row_number() OVER(ORDER BY UserId) rn, * FROM Users)
-
SELECT * FROM table WHERE UserName='Joe'
-
You can use INSERT, UPDATE or DELETE in last sentence by in spite of SELECT.
SQL Row_Number() function is to sort and assign an order number to data rows in related record set. So it is used to number rows, for example to identify the top 10 rows which have the highest order amount or identify the order of each customer which is the highest amount, etc.
If you want to sort the dataset and number each row by seperating them into categories we use Row_Number() with Partition By clause. For example, sorting orders of each customer within itself where the dataset contains all orders, etc.
SELECT
SalesOrderNumber,
CustomerId,
SubTotal,
ROW_NUMBER() OVER (PARTITION BY CustomerId ORDER BY SubTotal DESC) rn
FROM Sales.SalesOrderHeader
But as I understand you want to calculate the number of rows of grouped by a column. To visualize the requirement, if you want to see the count of all orders of the related customer as a seperate column besides order info, you can use COUNT() aggregation function with Partition By clause
For example,
SELECT
SalesOrderNumber,
CustomerId,
COUNT(*) OVER (PARTITION BY CustomerId) CustomerOrderCount
FROM Sales.SalesOrderHeader
This query:
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
will return all rows where the UserName is 'Joe' UNLESS you have no UserName='Joe'
They will be listed in order of UserID and the row_number field will start with 1 and increment however many rows contain UserName='Joe'
If it does not work for you then your WHERE command has an issue OR there is no UserID in the table. Check spelling for both fields UserID and UserName.
I need, if possible, a t-sql query that, returning the values from an arbitrary table, also returns a incremental integer column with value = 1 for the first row, 2 for the second, and so on.
This column does not actually resides in any table, and must be strictly incremental, because the ORDER BY clause could sort the rows of the table and I want the incremental row in perfect shape always.
The solution must run on SQL Server 2000
For SQL 2005 and up
SELECT ROW_NUMBER() OVER( ORDER BY SomeColumn ) AS 'rownumber',*
FROM YourTable
for 2000 you need to do something like this
SELECT IDENTITY(INT, 1,1) AS Rank ,VALUE
INTO #Ranks FROM YourTable WHERE 1=0
INSERT INTO #Ranks
SELECT SomeColumn FROM YourTable
ORDER BY SomeColumn
SELECT * FROM #Ranks
Order By Ranks
see also here Row Number
You can start with a custom number and increment from there, for example you want to add a cheque number for each payment you can do:
select #StartChequeNumber = 3446;
SELECT
((ROW_NUMBER() OVER(ORDER BY AnyColumn)) + #StartChequeNumber ) AS 'ChequeNumber'
,* FROM YourTable
will give the correct cheque number for each row.
Try ROW_NUMBER()
http://msdn.microsoft.com/en-us/library/ms186734.aspx
Example:
SELECT
col1,
col2,
ROW_NUMBER() OVER (ORDER BY col1) AS rownum
FROM tbl
It is ugly and performs badly, but technically this works on any table with at least one unique field AND works in SQL 2000.
SELECT (SELECT COUNT(*) FROM myTable T1 WHERE T1.UniqueField<=T2.UniqueField) as RowNum, T2.OtherField
FROM myTable T2
ORDER By T2.UniqueField
Note: If you use this approach and add a WHERE clause to the outer SELECT, you have to added it to the inner SELECT also if you want the numbers to be continuous.