Mujstart.cz blog http://www.mujstart.cz/blog Feel free to stop by! Wed, 04 Jan 2012 20:11:45 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Aggregate always returns a row even if no rows were aggregated http://www.mujstart.cz/blog/2012/01/aggregate-always-returns-a-row-even-if-no-rows-were-aggregated/ http://www.mujstart.cz/blog/2012/01/aggregate-always-returns-a-row-even-if-no-rows-were-aggregated/#comments Wed, 04 Jan 2012 20:11:45 +0000 Jan Novak http://www.mujstart.cz/blog/?p=362 Assign a value into variable from empty set cause the value remains the same.
Assign a value into variable from empty set which include an aggregate cause the value will be set to the value returned from aggregate. One row is returned everytime, even if no rows were aggregated.

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declare @x int
declare @table table(
	a int not null
)
 
insert into @table values(10)
 
--1)
set @x =-1
select 
	@x = min(a)
from
	@table
where 
	1=2
 
select @x
 
--2)
set @x =-1
select 
	@x = a
from
	@table
where 
	1=2
 
select @x
 
/*
-----------
NULL
 
-----------
-1
*/

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]]> http://www.mujstart.cz/blog/2012/01/aggregate-always-returns-a-row-even-if-no-rows-were-aggregated/feed/ 0 XPath expression for XQuery may cause high subtree cost http://www.mujstart.cz/blog/2012/01/xpath-expression-for-xquery-may-cause-high-subtree-cost/ http://www.mujstart.cz/blog/2012/01/xpath-expression-for-xquery-may-cause-high-subtree-cost/#comments Tue, 03 Jan 2012 19:49:19 +0000 Jan Novak http://www.mujstart.cz/blog/?p=350 There are a few ways how to write Xpath expression. Not every expression may return expected data. Here is a review and Subtree cost in execution plan (SQL Server 2008 R2, 64bit) for each tested method. Xml contains 100 nodes, some of them are empty:

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declare @x xml
set @x = N'<root>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>
			<item>D8749A19-B608-40D0-90F3-B66791303342</item>
			<item>63C3002A-98CA-4BCA-B05A-0AB5EBB43B65</item>			
			<item>77B04F73-206C-4992-A9DF-3FA2E73313DD</item>
			<item></item>
			<item>DB61F27A-C282-4D0D-89C2-FC1C624FA119</item>			
		  </root>'
 
--With defined singletons:
--First node
select @x.value(N'(root[1]/item[1]/text()[1])', N'UniqueIdentifier') 
--Select estimated subtree cost: 0.42
--If in the element is empty value, it is converted sucesfully to Null due text() 
--at the end of Xpath expression.
--more here http://www.xquery.com/tips_and_tricks/using_text_in_XPath.html
 
select @x.value(N'(root[1]/item[1]/text()[1])[1]', N'UniqueIdentifier') 
--Select estimated subtree cost: 0.42
--If in the element is empty value, it is converted sucesfully to Null due text()
--at the end of Xpath expression.
 
select @x.value(N'(root[1]/item[1])', N'UniqueIdentifier') 
--Select estimated subtree cost: 1.23 
--If in the element is empty value, the statement fails with message 
--"Conversion failed when converting from a character string to uniqueidentifier."
 
--Node 93:
select @x.value(N'(root[1]/item[93]/text()[1])', N'UniqueIdentifier') 
--Select estimated subtree cost: 1.68
--This Subtree cost stay the same with node 990.
 
select @x.value(N'(root[1]/item[93]/text()[1])[1]', N'UniqueIdentifier') 
--Select estimated subtree cost: 1.69
 
select @x.value(N'(root[1]/item[93])', N'UniqueIdentifier') 
--Select estimated subtree cost: 4.31
 
--------------------------------------------------------------------------
 
--There are not defined singletons, it may cause not expected behaviour.
--First node
select @x.value(N'(root/item/text())[1]', N'UniqueIdentifier') 
--Select estimated subtree cost: 0.005 
--May return unexpected data, more bellow.
 
select @x.value(N'(root/item)[1]', N'UniqueIdentifier') 
--Select estimated subtree cost: 1.02
--If in the element is empty value, the statement fails with message 
--"Conversion failed when converting from a character string to uniqueidentifier."
 
--Node 93:
select @x.value(N'(root/item/text())[93]', N'UniqueIdentifier') 
--Select estimated subtree cost: 1.004 
--XPath selects only nodes with text. This XPath will contains Null, because 
--93th node does not exist.
 
select @x.value(N'(root/item)[93]', N'UniqueIdentifier') 
--Select estimated subtree cost: 55.405
--If in the element is empty value, the statement fails with message 
--"Conversion failed when converting from a character string to uniqueidentifier."

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]]> http://www.mujstart.cz/blog/2012/01/xpath-expression-for-xquery-may-cause-high-subtree-cost/feed/ 0 Objects in master database with prefix sp_ are accessible in another databases http://www.mujstart.cz/blog/2011/12/objects-in-master-database-with-prefix-sp_-are-accessible-in-another-databases/ http://www.mujstart.cz/blog/2011/12/objects-in-master-database-with-prefix-sp_-are-accessible-in-another-databases/#comments Fri, 30 Dec 2011 20:31:15 +0000 Jan Novak http://www.mujstart.cz/blog/?p=343 Stored procedures, tables and views in master database with prefix sp_ are accessible in user databases. If in user database exists the same object as in the master database, the user database object has higher priority to be used. Here is a demo:

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use master
go
create procedure sp_v1
as
select 1
go
use myDb
go
exec sp_v1
--1
go
create procedure sp_v1
as
select 2
go
exec sp_v1
--2

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]]> http://www.mujstart.cz/blog/2011/12/objects-in-master-database-with-prefix-sp_-are-accessible-in-another-databases/feed/ 0 Srovnání Spoření a Spoření Plus v ZUNO bank http://www.mujstart.cz/blog/2011/12/srovnani-sporeni-a-sporeni-plus-v-zuno-bank/ http://www.mujstart.cz/blog/2011/12/srovnani-sporeni-a-sporeni-plus-v-zuno-bank/#comments Thu, 22 Dec 2011 11:06:49 +0000 Jan Novak http://www.mujstart.cz/blog/?p=339 ZUNO banka nabízí spoření s denním úročením, při kterém se do částky 127500 neplatí 15 % daň z úroků. Výše úrokové sazby je 2% p.a.

Dále nabízí spoření plus s úrokovou sazbou 2,5% p.a. s tím, že úroky jsou připisovány měsíčně a daněny 15% daní. Peníze v daném měsíci není možné převést jinam, jinak se úroky za daný měsíc nepřipíší.

Zde je srovnání vkladu 100 000 Kč:

Spoření plus (2,5% s daní 15 %):

Úrok za rok: 2500,00 Kč

Daň z úroku: 375,00 Kč (15%)

Čistý úrok za rok: 2125 Kč

Úrok za 31 dní: 180,47 Kč

 

Spoření (2% s daňovým zvýhodněním – denní připisování úroků):

Čistý úrok za rok: 2025,66 Kč

Úrok za 31 dní: 172,04 Kč

 

Spoření u jiné banky (2,0% s daní 15 %):

Úrok za rok: 2000,00 Kč

Daň z úroku: 300,00 Kč (15%)

Čistý úrok za rok: 1700 Kč

Úrok za 31 dní: 144,38 Kč

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]]> http://www.mujstart.cz/blog/2011/12/srovnani-sporeni-a-sporeni-plus-v-zuno-bank/feed/ 0 Format datetime in T-SQL http://www.mujstart.cz/blog/2011/12/format-datetime-in-t-sql/ http://www.mujstart.cz/blog/2011/12/format-datetime-in-t-sql/#comments Mon, 12 Dec 2011 18:25:12 +0000 Jan Novak http://www.mujstart.cz/blog/?p=330 
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Alter Function [dbo].[fn_format_date] (@Datetime DateTime, @FormatMask NVarChar(32))
Returns NvarChar(32)
As
Begin
    Declare @StringDate NVarChar(32)
    Set @StringDate = @FormatMask
 
    If (CharIndex (N'YYYY',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'YYYY', DateName(YY, @Datetime))
    End
    If (CharIndex (N'YY',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'YY', Right(DateName(YY, @Datetime),2))
	End  
    If (CharIndex (N'MM',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'MM', Right(N'0'+Convert(VARCHAR,DatePart(MM, @Datetime)),2))
	End
    If (CharIndex (N'M',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'M', Convert(VARCHAR,DatePart(MM, @Datetime)))
	End
    If (CharIndex (N'DD',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'DD', Right(N'0'+DateName(DD, @Datetime),2))
	End
    If (CharIndex (N'D',@StringDate) > 0)
    Begin
       Set @StringDate = Replace(@StringDate, N'D', DateName(DD, @Datetime))
    End
Return @StringDate
End
 
Go 
Set Nocount On
Declare @lDateTime Datetime = '20110506'
Print [dbo].[fn_format_date] (@lDateTime, 'MM/DD/YYYY')
Print [dbo].[fn_format_date] (@lDateTime, 'DD/MM/YYYY')
Print [dbo].[fn_format_date] (@lDateTime, 'M/DD/YYYY')
Print [dbo].[fn_format_date] (@lDateTime, 'M/D/YYYY') 
Print [dbo].[fn_format_date] (@lDateTime, 'M/D/YY')
Print [dbo].[fn_format_date] (@lDateTime, 'MM/DD/YY')
Print [dbo].[fn_format_date] (@lDateTime, 'YYYY/MM/DD')
Print [dbo].[fn_format_date] (@lDateTime, 'YYYYMMDD')
Print [dbo].[fn_format_date] (@lDateTime, 'YYYY-MM-DD')
 
/*
05/06/2011
06/05/2011
5/06/2011
5/6/2011
5/6/11
05/06/11
2011/05/06
20110506
2011-05-06
*/

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]]> http://www.mujstart.cz/blog/2011/12/format-datetime-in-t-sql/feed/ 0 Webinars worth seeing http://www.mujstart.cz/blog/2011/12/webinars-worth-seeing/ http://www.mujstart.cz/blog/2011/12/webinars-worth-seeing/#comments Thu, 08 Dec 2011 19:43:11 +0000 Jan Novak http://www.mujstart.cz/blog/?p=323 There are two webinars which I saw recently and which interrested me:

SQL Azure from Richard Iwasa, Senior Consultant, Solution Architect, Ideaca:
https://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032497373&Culture=en-CA
It contains deep info about SQL Azure and it is worth seeing.

Microsoft Virtual Academy also offers more free videos and best practices courses about SQL Azure: https://www.microsoftvirtualacademy.com/tracks/introduction-to-sql-azure

Performance query tunning (it does not contain internals, but contains common principles for query tunning):
http://marketo.confio.com/OnDemand_QueryPerformance_Triplett.html

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]]> http://www.mujstart.cz/blog/2011/12/webinars-worth-seeing/feed/ 0 @@RowCount and For Xml Path clause http://www.mujstart.cz/blog/2011/12/rowcount-and-for-xml-path-clause/ http://www.mujstart.cz/blog/2011/12/rowcount-and-for-xml-path-clause/#comments Thu, 08 Dec 2011 19:31:47 +0000 Jan Novak http://www.mujstart.cz/blog/?p=321 @@RowCount returns the number of rows affected by the last statement (BOL).

The documentation does not specify behaviour for FOR XML clause in the SELECT statement. When FOR XML clause is used, the behaviour is the same. The FOR XML clause converts the result into one row, but @@RowCount contains number of all affected rows in the SELECT statement.

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SELECT Top 100
	[number]
FROM 
	[master].[dbo].[spt_values] 
ORDER BY 
	[number] Asc
FOR XML PATH('')  
 
SELECT @@ROWCOUNT
--100

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]]> http://www.mujstart.cz/blog/2011/12/rowcount-and-for-xml-path-clause/feed/ 0 Paste UniqueIdentifier into string http://www.mujstart.cz/blog/2011/12/pasteuniqueidentifier-into-string/ http://www.mujstart.cz/blog/2011/12/pasteuniqueidentifier-into-string/#comments Thu, 08 Dec 2011 17:09:42 +0000 Jan Novak http://www.mujstart.cz/blog/?p=325 One of the possible ways to paste UniqueIdentifier into text string is:

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Declare @lId UniqueIdentifier = NewId()
Declare @x NVarChar(Max) =
	N'
	Select
		[id]
	From
		[table]
	Where
		[column] = '+IsNull(N'N'''+Cast(@lId As NVarChar(64))+'''', 'Null')
Print @x
/*
	Select
		[id]
	From
		[table]
	Where
		[column] = N'094FDFB4-7665-4E6A-89E0-B6A6C231D617'
*/

If Null is in the variable, the output will be:

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Declare @lId UniqueIdentifier
Declare @x NVarChar(Max) =
	N'
	Select
		[id]
	From
		[table]
	Where
		[column] = '+IsNull(N'N'''+Cast(@lId As NVarChar(64))+'''', 'Null')
Print @x
/*
	Select
		[id]
	From
		[table]
	Where
		[column] = Null
*/

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]]> http://www.mujstart.cz/blog/2011/12/pasteuniqueidentifier-into-string/feed/ 0 Roadmap to Denali Webcast Series http://www.mujstart.cz/blog/2011/11/roadmap-to-denali-webcast-series/ http://www.mujstart.cz/blog/2011/11/roadmap-to-denali-webcast-series/#comments Tue, 08 Nov 2011 19:48:01 +0000 Jan Novak http://www.mujstart.cz/blog/?p=319 Microsoft Canada Inc. offers free five live webcasts to help understand the benefits included in the next release of  SQL Server 2012 (Denali), commencing November 9th through December 7th at 1:00 pm EST.

More information, schedule and registration on:

https://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032497363&Culture=en-CA#

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]]> http://www.mujstart.cz/blog/2011/11/roadmap-to-denali-webcast-series/feed/ 0 Complete Showplan Operators by Fabiano Amorim http://www.mujstart.cz/blog/2011/11/complete-showplan-operators-by-fabiano-amorim/ http://www.mujstart.cz/blog/2011/11/complete-showplan-operators-by-fabiano-amorim/#comments Sun, 06 Nov 2011 17:52:40 +0000 Jan Novak http://www.mujstart.cz/blog/?p=316 There is a new free e-book Complete Showplan Operators written by Fabiano Amorim(SQL Server MVP).  More details are here including link for download: http://www.simple-talk.com/books/sql-books/complete-showplan-operators/

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