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• Alias a linked Server in SQL server management studio?

  - by absentmindeduk

  Hoping someone can help - is there a way in SQL server management studio 2008 R2 that I can alias a linked SQL server? I have a server, added by IP address, to which I do not have the login credentials - however as the connection is already setup I can login ok. Issue is that, this is a dev environment, prior to a live deployment and the IP I have as a linked server needs to be 'accessible' by my stored procs under a different name, eg 'myserver' not 192.168.xxx.xxx... Any help much appreciated.

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• .Net Windows Service Throws EventType clr20r3 system.data.sqlclient.sql error

  - by William Edmondson

  I have a .Net/c# 2.0 windows service. The entry point is wrapped in a try catch block yet when I look at the server's application event log I seem a number of "EventType clr20r3" errors that are causing the service to die unexpectedly. The catch block has a "catch (Exception ex)". Each sql commands is of the type "CommandType.StoredProcedure" and are executed with SqlDataReader's. These sproc calls function correctly 99% of time and have all been thoroughly unit tested, profiled, and QA'd. I additionally wrapped these calls in try catch blocks just to be sure and am still experiencing these unhandled exceptions. This only in our production environment and cannot be duplicated in our dev or staging environments (even under heavy load). Why would my error handling not catch this particular error? Is there anyway to capture more detail as to the root cause of the problem? Here is an example of the event log: EventType clr20r3, P1 RDC.OrderProcessorService, P2 1.0.0.0, P3 4ae6a0d0, P4 system.data, P5 2.0.0.0, P6 4889deaf, P7 2490, P8 2c, P9 system.data.sqlclient.sql, P10 NIL. Additionally The Order Processor service terminated unexpectedly. It has done this 1 time(s). The following corrective action will be taken in 60000 milliseconds: Restart the service.

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• T-SQL: Compute Subtotals For A Range Of Rows

  - by John Dibling

  MSSQL 2008. I am trying to construct a SQL statement which returns the total of column B for all rows where column A is between 2 known ranges. The range is a sliding window, and should be recomputed as it might be using a loop. Here is an example of what I'm trying to do, much simplified from my actual problem. Suppose I have this data: table: Test Year Sales ----------- ----------- 2000 200 2001 200 2002 200 2003 200 2004 200 2005 200 2006 200 2007 200 2008 200 2009 200 2010 200 2011 200 2012 200 2013 200 2014 200 2015 200 2016 200 2017 200 2018 200 2019 200 I want to construct a query which returns 1 row for every decade in the above table, like this: Desired Results: DecadeEnd TotalSales --------- ---------- 2009 2000 2010 2000 Where the first row is all the sales for the years 2000-2009, the second for years 2010-2019. The DecadeEnd is a sliding window that moves forward by a set ammount for each row in the result set. To illustrate, here is one way I can accomplish this using a loop: declare @startYear int set @startYear = (select top(1) [Year] from Test order by [Year] asc) declare @endYear int set @endYear = (select top(1) [Year] from Test order by [Year] desc) select @startYear, @endYear create table DecadeSummary (DecadeEnd int, TtlSales int) declare @i int -- first decade ends 9 years after the first data point set @i = (@startYear + 9) while @i <= @endYear begin declare @ttlSalesThisDecade int set @ttlSalesThisDecade = (select SUM(Sales) from Test where(Year <= @i and Year >= (@i-9))) insert into DecadeSummary values(@i, @ttlSalesThisDecade) set @i = (@i + 9) end select * from DecadeSummary This returns the data I want: DecadeEnd TtlSales ----------- ----------- 2009 2000 2018 2000 But it is very inefficient. How can I construct such a query?

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• LINQ To SQL ignore unique constraint exception and continue

  - by Martin

  I have a single table in a database called Users Users ------ ID (PK, Identity) Username (Unique Index) I have setup a unique index on the Username table to prevent duplicates. I am then enumerating through a collection and creating a new user in the database for each item. What I want to do is just insert a new user and ignore the exception if the unique key constraint is violated (as it's clearly a duplicate record in that case). This is to avoid having to craft where not exists kind of queries. First off, is this going to be any more efficient or should my insert code be checking for duplicates instead? I'm drawn more to the database having that logic as this prevents any other type of client from inserting duplicate data. My other issue is related to LINQ To SQL. I have the following code: public class TestRepo { DatabaseDataContext database = new DatabaseDataContext(); public void Add(string username) { database.Users.InsertOnSubmit(new User() { Username = username }); } public void Save() { database.SubmitChanges(); } } And then I iterate over a collection and insert new users, ignoring any exceptions: TestRepo repo = new TestRepo(); foreach (var name in new string[] { "Tim", "Bob", "John" }) { try { repo.Add(name); repo.Save(); } catch { } } The first time this is run, great I have three users in the table. If I remove the second one and run this code again, nothing is inserted. I expected the first insert to fail with the exception, the second to succeed (as I just removed that item from the DB) and the third to then fail. What seems to be happening is that once the SqlException is thrown (even though the loop continues to iterate) all of the next inserts fail - even when there isn't a row in the table that would cause a unique violation. Can anyone explain this? P.S. The only workaround I could find was to instantiate the repo each time before the insert, then it worked exactly as excepted - indicating that it's something to do with the LINQ To SQL DataContext. Thanks.

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• Error Handling in T-SQL Scalar Function

  - by hydroparadise

  Ok.. this question could easily take multiple paths, so I will hit the more specific path first. While working with SQL Server 2005, I'm trying to create a scalar funtion that acts as a 'TryCast' from varchar to int. Where I encounter a problem is when I add a TRY block in the function; CREATE FUNCTION u_TryCastInt ( @Value as VARCHAR(MAX) ) RETURNS Int AS BEGIN DECLARE @Output AS Int BEGIN TRY SET @Output = CONVERT(Int, @Value) END TRY BEGIN CATCH SET @Output = 0 END CATCH RETURN @Output END Turns out theres all sorts of things wrong with this statement including "Invalid use of side-effecting or time-dependent operator in 'BEGIN TRY' within a function" and "Invalid use of side-effecting or time-dependent operator in 'END TRY' within a function". I can't seem to find any examples of using try statements within a scalar function, which got me thinking, is error handling in a function is possible? The goal here is to make a robust version of the Convert or Cast functions to allow a SELECT statement carry through depsite conversion errors. For example, take the following; CREATE TABLE tblTest ( f1 VARCHAR(50) ) GO INSERT INTO tblTest(f1) VALUES('1') INSERT INTO tblTest(f1) VALUES('2') INSERT INTO tblTest(f1) VALUES('3') INSERT INTO tblTest(f1) VALUES('f') INSERT INTO tblTest(f1) VALUES('5') INSERT INTO tblTest(f1) VALUES('1.1') SELECT CONVERT(int,f1) AS f1_num FROM tblTest DROP TABLE tblTest It never reaches point of dropping the table because the execution gets hung on trying to convert 'f' to an integer. I want to be able to do something like this; SELECT u_TryCastInt(f1) AS f1_num FROM tblTest fi_num __________ 1 2 3 0 5 0 Any thoughts on this? Is there anything that exists that handles this? Also, I would like to try and expand the conversation to support SQL Server 2000 since Try blocks are not an option in that scenario. Thanks in advance.

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• Atomic UPSERT in SQL Server 2005

  - by rabidpebble

  What is the correct pattern for doing an atomic "UPSERT" (UPDATE where exists, INSERT otherwise) in SQL Server 2005? I see a lot of code on SO (e.g. see http://stackoverflow.com/questions/639854/tsql-check-if-a-row-exists-otherwise-insert) with the following two-part pattern: UPDATE ... FROM ... WHERE <condition> -- race condition risk here IF @@ROWCOUNT = 0 INSERT ... or IF (SELECT COUNT(*) FROM ... WHERE <condition>) = 0 -- race condition risk here INSERT ... ELSE UPDATE ... where will be an evaluation of natural keys. None of the above approaches seem to deal well with concurrency. If I cannot have two rows with the same natural key, it seems like all of the above risk inserting rows with the same natural keys in race condition scenarios. I have been using the following approach but I'm surprised not to see it anywhere in people's responses so I'm wondering what is wrong with it: INSERT INTO <table> SELECT <natural keys>, <other stuff...> FROM <table> WHERE NOT EXISTS -- race condition risk here? ( SELECT 1 FROM <table> WHERE <natural keys> ) UPDATE ... WHERE <natural keys> (Note: I'm assuming that rows will not be deleted from this table. Although it would be nice to discuss how to handle the case where they can be deleted -- are transactions the only option? Which level of isolation?) Is this atomic? I can't locate where this would be documented in SQL Server documentation.

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• Fastest way to remove non-numeric characters from a VARCHAR in SQL Server

  - by Dan Herbert

  I'm writing an import utility that is using phone numbers as a unique key within the import. I need to check that the phone number does not already exist in my DB. The problem is that phone numbers in the DB could have things like dashes and parenthesis and possibly other things. I wrote a function to remove these things, the problem is that it is slow and with thousands of records in my DB and thousands of records to import at once, this process can be unacceptably slow. I've already made the phone number column an index. I tried using the script from this post: http://stackoverflow.com/questions/52315/t-sql-trim-nbsp-and-other-non-alphanumeric-characters But that didn't speed it up any. Is there a faster way to remove non-numeric characters? Something that can perform well when 10,000 to 100,000 records have to be compared. Whatever is done needs to perform fast. Update Given what people responded with, I think I'm going to have to clean the fields before I run the import utility. To answer the question of what I'm writing the import utility in, it is a C# app. I'm comparing BIGINT to BIGINT now, with no need to alter DB data and I'm still taking a performance hit with a very small set of data (about 2000 records). Could comparing BIGINT to BIGINT be slowing things down? I've optimized the code side of my app as much as I can (removed regexes, removed unneccessary DB calls). Although I can't isolate SQL as the source of the problem anymore, I still feel like it is.

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• Ordering of month/year pairs in T-SQL query

  - by Surya sasidhar

  I am writing a stored procedure for displaying month and year. It is working, but it is not returning the rows in the desired order. ALTER procedure [dbo].[audioblog_getarchivedates] as begin select DateName(Month,a.createddate) + ' ' + DateName(Year,a.createddate) as ArchiveDate from audio_blog a group by DateName(Month,a.createddate) + ' ' + DateName(Year,a.createddate) order by DateName(Month,a.createddate) + ' ' + DateName(Year,a.createddate) desc end Results will come like this: March 2010 January 2010 February 2010 But that is not in a order (desc).

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• Can I select 0 columns in SQL Server?

  - by Woody Zenfell III

  I am hoping this question fares a little better than the similar Create a table without columns. Yes, I am asking about something that will strike most as pointlessly academic. It is easy to produce a SELECT result with 0 rows (but with columns), e.g. SELECT a = 1 WHERE 1 = 0. Is it possible to produce a SELECT result with 0 columns (but with rows)? e.g. something like SELECT NO COLUMNS FROM Foo. (This is not valid T-SQL.) I came across this because I wanted to insert several rows without specifying any column data for any of them. e.g. (SQL Server 2005) CREATE TABLE Bar (id INT NOT NULL IDENTITY PRIMARY KEY) INSERT INTO Bar SELECT NO COLUMNS FROM Foo -- Invalid column name 'NO'. -- An explicit value for the identity column in table 'Bar' can only be specified when a column list is used and IDENTITY_INSERT is ON. One can insert a single row without specifying any column data, e.g. INSERT INTO Foo DEFAULT VALUES. One can query for a count of rows (without retrieving actual column data from the table), e.g. SELECT COUNT(*) FROM Foo. (But that result set, of course, has a column.) I tried things like INSERT INTO Bar () SELECT * FROM Foo -- Parameters supplied for object 'Bar' which is not a function. -- If the parameters are intended as a table hint, a WITH keyword is required. and INSERT INTO Bar DEFAULT VALUES SELECT * FROM Foo -- which is a standalone INSERT statement followed by a standalone SELECT statement. I can do what I need to do a different way, but the apparent lack of consistency in support for degenerate cases surprises me. I read through the relevant sections of BOL and didn't see anything. I was surprised to come up with nothing via Google either.

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• T-SQL While Loop and concatenation

  - by JustinT

  I have a SQL query that is supposed to pull out a record and concat each to a string, then output that string. The important part of the query is below. DECLARE @counter int; SET @counter = 1; DECLARE @tempID varchar(50); SET @tempID = ''; DECLARE @tempCat varchar(255); SET @tempCat = ''; DECLARE @tempCatString varchar(5000); SET @tempCatString = ''; WHILE @counter <= @tempCount BEGIN SET @tempID = ( SELECT [Val] FROM #vals WHERE [ID] = @counter); SET @tempCat = (SELECT [Description] FROM [Categories] WHERE [ID] = @tempID); print @tempCat; SET @tempCatString = @tempCatString + '<br/>' + @tempCat; SET @counter = @counter + 1; END When the script runs, @tempCatString outputs as null while @tempCat always outputs correctly. Is there some reason that concatenation won't work inside a While loop? That seems wrong, since incrementing @counter works perfectly. So is there something else I'm missing?

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• How to Convert using of SqlLit to Simple SQL command in C#

  - by Nasser Hajloo

  I want to get start with DayPilot control I do not use SQLLite and this control documented based on SQLLite. I want to use SQL instead of SQL Lite so if you can, please do this for me. main site with samples http://www.daypilot.org/calendar-tutorial.html The database contains a single table with the following structure CREATE TABLE event ( id VARCHAR(50), name VARCHAR(50), eventstart DATETIME, eventend DATETIME); Loading Events private DataTable dbGetEvents(DateTime start, int days) { SQLiteDataAdapter da = new SQLiteDataAdapter("SELECT [id], [name], [eventstart], [eventend] FROM [event] WHERE NOT (([eventend] <= @start) OR ([eventstart] >= @end))", ConfigurationManager.ConnectionStrings["db"].ConnectionString); da.SelectCommand.Parameters.AddWithValue("start", start); da.SelectCommand.Parameters.AddWithValue("end", start.AddDays(days)); DataTable dt = new DataTable(); da.Fill(dt); return dt; } Update private void dbUpdateEvent(string id, DateTime start, DateTime end) { using (SQLiteConnection con = new SQLiteConnection(ConfigurationManager.ConnectionStrings["db"].ConnectionString)) { con.Open(); SQLiteCommand cmd = new SQLiteCommand("UPDATE [event] SET [eventstart] = @start, [eventend] = @end WHERE [id] = @id", con); cmd.Parameters.AddWithValue("id", id); cmd.Parameters.AddWithValue("start", start); cmd.Parameters.AddWithValue("end", end); cmd.ExecuteNonQuery(); } }

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• Linq to SQL not inserting data onto the DB

  - by Jesus Rodriguez

  Hello! I have a little / weird behaviour here and Im looking over internet and SO and I didn't find a response. I have to admit that this is my first time using databases, I know how to use them with SQL but never used it actually. Anyway, I have a problem with my app inserting data, I just created a very simple project for testing that and no solution yet. I have an example database with Sql Server Id - int (identity primary key) Name - nchar(10) (not null) The table is called "Person", simple as pie. I have this: static void Main(string[] args) { var db = new ExampleDBDataContext {Log = Console.Out}; var jesus = new Person {Name = "Jesus"}; db.Persons.InsertOnSubmit(jesus); db.SubmitChanges(); var query = from person in db.Persons select person; foreach (var p in query) { Console.WriteLine(p.Name); } } As you can see, nothing extrange. It show Jesus in the console. But if you see the table data, there is no data, just empty. I comment the object creation and insertion and the foreach doesn't print a thing (normal, there is no data in the database) The weird thing is that I created a row in the database manually and the Id was 2 and no 1 (Was the linq really playing with the database but it didn't create the row?) There is the log: INSERT INTO [dbo].Person VALUES (@p0) SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value] -- @p0: Input NChar (Size = 10; Prec = 0; Scale = 0) [Jesus] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.4926 SELECT [t0].[Id], [t0].[Name] FROM [dbo].[Person] AS [t0] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.4926 I am really confused, All the blogs / books use this kind of snippet to insert an element to a database. Thank you for helping.

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• SQL Query problem: How to merge two lists.

  - by ProfK

  I have a base table of Participants and Answers, with the following structure: ParticipantId, BusUnitId, QuestionNum, Answer. In this table, QuestionNum ranges, say, from 1 to 6. I also have two other tables that sort of link QuestionNum to the actual question table, BusUnitQuestions, and ParticipantQuestions. For each QuestionNum, I must get the actual question text, based on QuestionId. BusUnitId, QuestionId ParticipantId, QuestionId Now assuming records with QuestionNum from 1 to 6. BusUnitQuestions has 3 records, so QuestionNum 1 to 3 must join to Question on the QuestionId's from BusUnitQuestions, and QuestionNum 4 to 6 must join to Question on the QuestionId's from ParticipantQuestions. I assume I need to use ROW_NUMBER() in the subquery from BusUnitQuestions to join to my answer table, but I'm lost after that. If anyone at all understands me, do you have any suggestions?

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• What does SQL Server's BACKUPIO wait type mean?

  - by solublefish

  I'm using Sql Server 2008 ("R1"), with some maintenance plans that back up my databases to a network share. Some of my backup jobs show long waits of type "BACKUPIO". Of course it seems like this is an I/O subsystem limitation, but I'm skeptical. Perfmon stats for I/O on the production (source) server are well within normal trends for that server. The destination server shows a sustained 7MB/s write rate, which seems incredibly low, even for a slow disk. The network link is gigabit ethernet and nowhere near saturated. The few docs I've turned up about BACKUPIO indicate that it's not specifically a wait on I/O, surprisingly enough. This MSFT doc says it's abnormal unless you're using a tape drive, which I'm not. But it doesn't say (or I don't understand) exactly what resource is missing. http://www.docstoc.com/docs/24580659/Performance-Tuning-in-SQL-Server-2005 And this piece says it's not related to I/O performance at all. http://www.informit.com/articles/article.aspx?p=686168&seqNum=5 "Note that BACKUPIO and IO_AUDIT_MUTEX are not related to IO performance." Anyway, does anyone know what BACKUPIO actually means and/or what I can do to diagnose or eliminate it?

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• Question about SQL Server HierarchyID depth-first performance

  - by AndalusianCat

  I am trying to implement hierarchyID in a table (dbo.[Message]) containing roughly 50,000 rows (will grow substantially in the future). However it takes 30-40 seconds to retrieve about 25 results. The root node is a filler in order to provide uniqueness, therefor every subsequent row is a child of that dummy row. I need to be able to traverse the table depth-first and have made the hierarchyID column (dbo.[Message].MessageID) the clustering primary key, have also added a computed smallint (dbo.[Message].Hierarchy) which stores the level of the node. Usage: A .Net application passes through a hierarchyID value into the database and I want to be able to retrieve all (if any) children AND parents of that node (besides the root, as it is filler). A simplified version of the query I am using: @MessageID hierarchyID /* passed in from application */ SELECT m.MessageID, m.MessageComment FROM dbo.[Message] as m WHERE m.Messageid.IsDescendantOf(@MessageID.GetAncestor((@MessageID.GetLevel()-1))) = 1 ORDER BY m.MessageID From what I understand, the index should be detected automatically without a hint. From searching forums I have seen people utilizing index hints, at least in the case of breadth-first indexes, as apparently CLR calls may be opaque to the query optimizer. I have spent the past few days trying to find a solution for this issue, but to no avail. I would greatly appreciate any assistance, and as this is my first post, I apologize in advance if this would be considered a 'noobish' question, I have read the MS documentation and searched countless forums, but have not came across a succinct description of the specific issue.

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• SQL Server 2005 Reporting Services and the Report Viewer

  - by Kendra

  I am having an issue embedding my report into an aspx page. Here's my setup: 1 Server running SQL Server 2005 and SQL Server 2005 Reporting Services 1 Workstation running XP and VS 2005 The server is not on a domain. Reporting Services is a default installation. I have one report called TestMe in a folder called TestReports using a shared datasource. If I view the report in Report Manager, it renders fine. If I view the report using the http ://myserver/reportserver url it renders fine. If I view the report using the http ://myserver/reportserver?/TestReports/TestMe it renders fine. If I try to view the report using http ://myserver/reportserver/TestReports/TestMe, it just goes to the folder navigation page of the home directory. My web application is impersonating somebody specific to get around the server not being on a domain. When I call the report from the report viewer using http ://myserver/reportserver as the server and /TestReports/TestMe as the path I get this error: For security reasons DTD is prohibited in this XML document. To enable DTD processing set the ProhibitDtd property on XmlReaderSettings to false and pass the settings into XmlReader.Create method. When I change the server to http ://myserver/reportserver? I get this error when I run the report: Client found response content type of '', but expected 'text/xml'. The request failed with an empty response. I have been searching for a while and haven't found anything that fixes my issue. Please let me know if there is more information needed. Thanks in advance, Kendra

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• SQL Query slow in .NET application but instantaneous in SQL Server Management Studio

  - by user203882

  Here is the SQL SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.trustaccountlogid = ( SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.TrustAccountLogDate < '3/1/2010 12:00:00 AM' ) Basicaly there is a Users table a TrustAccount table and a TrustAccountLog table. Users: Contains users and their details TrustAccount: A User can have multiple TrustAccounts. TrustAccountLog: Contains an audit of all TrustAccount "movements". A TrustAccount is associated with multiple TrustAccountLog entries. Now this query executes in milliseconds inside SQL Server Management Studio, but for some strange reason it takes forever in my C# app and even timesout (120s) sometimes. Here is the code in a nutshell. It gets called multiple times in a loop and the statement gets prepared. cmd.CommandTimeout = Configuration.DBTimeout; cmd.CommandText = "SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID1 AND ta.TrustAccountID = @TrustAccountID1 AND tal.trustaccountlogid = (SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID2 AND ta.TrustAccountID = @TrustAccountID2 AND tal.TrustAccountLogDate < @TrustAccountLogDate2 ))"; cmd.Parameters.Add("@TrustAccountID1", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID1", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountID2", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID2", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountLogDate2", SqlDbType.DateTime).Value =TrustAccountLogDate; // And then... reader = cmd.ExecuteReader(); if (reader.Read()) { double value = (double)reader.GetValue(0); if (System.Double.IsNaN(value)) return 0; else return value; } else return 0;

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• SQL Server 2005 standard filegroups / files for performance on SAN

  - by Blootac

  Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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• SQL Server Clustered Index: (Physical) Data Page Order

  - by scherand

  I am struggling understanding what a clustered index in SQL Server 2005 is. I read the MSDN article Clustered Index Structures (among other things) but I am still unsure if I understand it correctly. The (main) question is: what happens if I insert a row (with a "low" key) into a table with a clustered index? The above mentioned MSDN article states: The pages in the data chain and the rows in them are ordered on the value of the clustered index key. And Using Clustered Indexes for example states: For example, if a record is added to the table that is close to the beginning of the sequentially ordered list, any records in the table after that record will need to shift to allow the record to be inserted. Does this mean that if I insert a row with a very "low" key into a table that already contains a gazillion rows literally all rows are physically shifted on disk? I cannot believe that. This would take ages, no? Or is it rather (as I suspect) that there are two scenarios depending on how "full" the first data page is. A) If the page has enough free space to accommodate the record it is placed into the existing data page and data might be (physically) reordered within that page. B) If the page does not have enough free space for the record a new data page would be created (anywhere on the disk!) and "linked" to the front of the leaf level of the B-Tree? This would then mean the "physical order" of the data is restricted to the "page level" (i.e. within a data page) but not to the pages residing on consecutive blocks on the physical hard drive. The data pages are then just linked together in the correct order. Or formulated in an alternative way: if SQL Server needs to read the first N rows of a table that has a clustered index it can read data pages sequentially (following the links) but these pages are not (necessarily) block wise in sequence on disk (so the disk head has to move "randomly"). How close am I? :)

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• sp_addlinkedserver on sql server 2005 giving problem

  - by Jit

  I am trying to create a link server of a remote database(both the servers are SQL serve2005). I am able to connect that remote server from my SQL Server management studio. I used the following syntax to create it. EXEC sp_addlinkedserver @server = N'LINKSQL2005', @srvproduct = N'', @provider = N'SQLNCLI', @provstr = N'SERVER=IP Address of remote server ;User ID=XXXXXX;Password=***' I have provided the IP addressntax. and user name and password in the above syntax. The link server is getting created. But when I try to execute a query on it I get the error below. Query Used. select * from LINKSQL2005.<DBName>.dbo.<TableName> OLE DB provider "SQLNCLI" for linked server "LINKSQL2005" returned message "Communication link failure". Msg 10054, Level 16, State 1, Line 0 TCP Provider: An existing connection was forcibly closed by the remote host. Msg 18456, Level 14, State 1, Line 0 Login failed for user 'sa'. OLE DB provider "SQLNCLI" for linked server "LINKSQL2005" returned message "Invalid connection string attribute". Pls help me, where am I making mistake.

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• Slow MySQL Query not using filesort

  - by Canadaka

  I have a query on my homepage that is getting slower and slower as my database table grows larger. tablename = tweets_cache rows = 572,327 this is the query I'm currently using that is slow, over 5 seconds. SELECT * FROM tweets_cache t WHERE t.province='' AND t.mp='0' ORDER BY t.published DESC LIMIT 50; If I take out either the WHERE or the ORDER BY, then the query is super fast 0.016 seconds. I have the following indexes on the tweets_cache table. PRIMARY published mp category province author So i'm not sure why its not using the indexes since mp, provice and published all have indexes? Doing a profile of the query shows that its not using an index to sort the query and is using filesort which is really slow. possible_keys = mp,province Extra = Using where; Using filesort I tried adding a new multie-colum index with "profiles & mp". The explain shows that this new index listed under "possible_keys" and "key", but the query time is unchanged, still over 5 seconds. Here is a screenshot of the profiler info on the query. http://i355.photobucket.com/albums/r469/canadaka_bucket/slow_query_profile.png Something weird, I made a dump of my database to test on my local desktop so i don't screw up the live site. The same query on my local runs super fast, milliseconds. So I copied all the same mysql startup variables from the server to my local to make sure there wasn't some setting that might be causing this. But even after that the local query runs super fast, but the one on the live server is over 5 seconds. My database server is only using around 800MB of the 4GB it has available. here are the related my.ini settings i'm using default-storage-engine = MYISAM max_connections = 800 skip-locking key_buffer = 512M max_allowed_packet = 1M table_cache = 512 sort_buffer_size = 4M read_buffer_size = 4M read_rnd_buffer_size = 16M myisam_sort_buffer_size = 64M thread_cache_size = 8 query_cache_size = 128M # Try number of CPU's*2 for thread_concurrency thread_concurrency = 8 # Disable Federated by default skip-federated key_buffer = 512M sort_buffer_size = 256M read_buffer = 2M write_buffer = 2M key_buffer = 512M sort_buffer_size = 256M read_buffer = 2M write_buffer = 2M

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• How to improve performance of non-scalar aggregations on denormalized tables

  - by The Lazy DBA

  Suppose we have a denormalized table with about 80 columns, and grows at the rate of ~10 million rows (about 5GB) per month. We currently have 3 1/2 years of data (~400M rows, ~200GB). We create a clustered index to best suit retrieving data from the table on the following columns that serve as our primary key... [FileDate] ASC, [Region] ASC, [KeyValue1] ASC, [KeyValue2] ASC ... because when we query the table, we always have the entire primary key. So these queries always result in clustered index seeks and are therefore very fast, and fragmentation is kept to a minimum. However, we do have a situation where we want to get the most recent FileDate for every Region, typically for reports, i.e. SELECT [Region] , MAX([FileDate]) AS [FileDate] FROM HugeTable GROUP BY [Region] The "best" solution I can come up to this is to create a non-clustered index on Region. Although it means an additional insert on the table during loads, the hit isn't minimal (we load 4 times per day, so fewer than 100,000 additional index inserts per load). Since the table is also partitioned by FileDate, results to our query come back quickly enough (200ms or so), and that result set is cached until the next load. However I'm guessing that someone with more data warehousing experience might have a solution that's more optimal, as this, for some reason, doesn't "feel right".

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• Help with complex sql query

  - by eugeneK

  To make story short, i'm building self-learning banner management system. Users will be able to insert these banners to their site when banners will be shown based on sales/impressions ratio. I have 4 tables Banners bannerID int bannerImage varchar.... SmartBanners smartBannerID int smartBannerArrayID int bannerID int impressionsCount int visibility tinyint (percents) SmartBannerArrays smartBannerArrayID int userID int Statistics bannerID int saleAmountPerDay decimal... Each night i need to generate new "visibility" for each SmartBanner based on whole SmartBannerArray that same user has. So i need to get sum of impressions and sales for each bannerID in SmartBannerArray. All comes to my mind is to use double cursor, one will loop thought SmartBannerArrays get needed values for sum of impressions and sales and then inner loop which will access each SmartBanner and change it's "visibility" percentage based on (sales/impressions)/(sumOfSales/sumOfImpressions)*100 Hope you get the picture... Is there any other way to design better tables or not to use double cursor to avoid server overload ?

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• SQL Distinct keyword in assignment statement

  - by Brandi

  I have a query that works: DECLARE @ProductID int SET @ProductID = '1234' SELECT DISTINCT TOP 12 a.ProductID FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE b.ProductID = @ProductID) AND a.ProductID != @ProductID It returns a list of 12 product numbers, all unique. I need to store these results in a variable, comma separated, because that's what 3rd party stored procedure needs. So I have this: DECLARE @ProductID int DECLARE @relatedprods varchar(8000) SET @ProductID = '1234' SET @relatedprods = '' SELECT TOP 12 @relatedprods = @relatedprods + CONVERT(VARCHAR(20), a.ProductID) + ', ' FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE B.ProductID = @ProductID) AND a.ProductID != @ProductID SELECT @relatedprods Now, none of these are distinct, but it is returning 12 rows. Now I add the 'distinct' back in, like in the first query: DECLARE @ProductID int DECLARE @relatedprods varchar(8000) SET @ProductID = '1234' SET @relatedprods = '' SELECT DISTINCT TOP 12 @relatedprods = @relatedprods + CONVERT(VARCHAR(20), a.ProductID) + ', ' FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE B.ProductID = @ProductID) AND a.ProductID != @ProductID SELECT @relatedprods Only one product is returned in the comma separated list! Does 'distinct' not work in assignment statements? What did I do wrong? Or is there a way to get around this? Thanks in advance!

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• SQL query to return all rows that contain duplicate data from one field

  - by TheDudeAbides

  I have a table with card numbers and names. Some of those names are the same, meaning they have multiple cards. How can I select all the rows where the name occurs more than once?

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