Concurrency Puzzle (ODBC API Related)
Jul 20, 2005
I hope this is not outside the scope of this newsgroup.
have been useing BulkAdd with ms-access with good success.
Until now that I;m switching to MSDE which is on a shared server.
The problem is that MSDE gives an error:
Invalid attribute/option identifier, sql state=HY092
which corresponds to:
SQL_ATTR_CONCURRENCY statement attribute was set to SQL_CONCUR_READ_ONLY.
but my BulkAdd routine explicitly has a call to:
SQLSetStmtAttr(stHndl, SQL_ATTR_CONCURRENCY, SQL_CONCUR_LOCK , iRet)
I cannot imagine how the concurrency is readonly.
Could it be that I'm looking at the wrong place or the wrong attribute???
Thanks in adv.
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Jul 23, 2005
I have a customer who has a SQL Server 2000 DB and we are needing toget to this DB through ODBC. I had setup a DSN last week thatconnected fine to this DB, and was preparing to build a script tomanage transfers of data to and from one table to another.The then began to have troubles with their DB Backup (this is not atall related to the issue at hand). The problem they claim was that the"sa" was needing to have certain roles applied to it that were not partof it's default properties. My understanding is that the "sa" is theKing of the Kingdom sotospeak, and has all rights, permissions, rolecapabilities, etc...To make a long story short she tried to apply the write and read rolesto the "sa" and it would not allow for this to be applied. She thenapplied a password to the "sa" account (previous it did not have oneand was set to blank) and upon doing this she then removed the passwordand set it back to blank.Since she made these changes we have not been able to connect to her DBvia our DSN. When we get to the point of telling the DSN to use SQLAuthentication, and apply the sa account for use with a blank password- it comes back with an error similar to "database is not available orpassword is incorrect".Has anyone had this problem before, and if so is there any simpleresolve? Something other than the customer having to restore a previousbackup of the DB?Much thanks in advance...
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Mar 31, 2004
What's the MS SQL Server SQL for making rows
xxx yyy 1 zzz
xxx yyy 2 zzz
xxx yyy 3 zzz
into a row
xxx yyy 1,2,3 zzz
Or is there another way
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Aug 6, 2001
Hello all, I have a puzzle that needs solving please. I have a Stored Procedure and it works fine and produces what I want to see. I have two servers replicating and when the stored procedure is ran on the other server, it produces nothing at all but the data is verified the same. So I go to query analyzer and copy the following sql statement from the stored procedures and put in the variables it asks for and I get nothing on either server. Here is the statement:
CREATE PROCEDURE sp_Transfer (
@Weekending datetime,
@Transfer datetime)
AS
select jobs.jobnumber, activities.weekending,
activities.material,
case employees.type when '1099' then case left(lineitems.item,4) when '2392' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,4) when '2391' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,4) when '3172' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,5) when 'ECAD2' then (lineitems.quantity * lineitems.draft1099) else
(lineitems.quantity * lineitems.labor1099) end else
case left(lineitems.item,4) when '2392' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,4) when '2391' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,4) when '3172' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,5) when 'ECAD2' then (lineitems.quantity * lineitems.draft) else
(lineitems.quantity * lineitems.labor) end end end end end end end end as labor,
(lineitems.quantity * lineitems.vehicle) as Vehicle,
(activities.meals + activities.lodging) as PerDiem,
(employees.state) as FState, (states.state) as TState
from jobs
inner join activities on jobs.jobid = activities.jobid
left outer join employees on activities.employeeid = employees.employeeid
left outer join lineitems on activities.activityid = lineitems.activityid
inner join states on jobs.billingstateid = states.stateid
where (activities.weekending = @Weekending or activities.transferdate = @Transfer or jobs.transferdate = @Transfer)
and jobs.billingstateid <> employees.stateid and lineitems.quantity <> null
GO
Can anyone help tell me why this happens or has anyone ever experienced this before?
Thank you in advance!!!!!!
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Dec 11, 2002
Can anyone solve this puzzle with SQL only - no temp tables and no cursors
(sent to me by a friend)?
I would have done it with a cursor on SQL Server but the rules stipulate not using a cursor. Can this be done with just SQL?
You have a table:
First Name Last Name
John Doe
Jeff Smith
etc..
Is it possible to write a query in SQL which assigns serial numbers 1; 2; 3; to the rows(in any sequence)? So the output should look like this:
Number First Name Last Name
1 John Doe
2 Jeff Smith
etc..
Note that your query must work with any data for the input table. You cannot rely on the fact that there are only two rows. Number cannot be a IDENTITY column.
Thanks!
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Aug 6, 2001
Hello all, I have a puzzle that needs solving please. I have a Stored Procedure and it works fine and produces what I want to see. I have two servers replicating and when the stored procedure is ran on the other server, it produces nothing at all but the data is verified the same. So I go to query analyzer and copy the following sql statement from the stored procedures and put in the variables it asks for and I get nothing on either server. Here is the statement:
CREATE PROCEDURE sp_Transfer (
@Weekending datetime,
@Transfer datetime)
AS
select jobs.jobnumber, activities.weekending,
activities.material,
case employees.type when '1099' then case left(lineitems.item,4) when '2392' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,4) when '2391' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,4) when '3172' then (lineitems.quantity * lineitems.draft1099) end else
case employees.type when '1099' then case left(lineitems.item,5) when 'ECAD2' then (lineitems.quantity * lineitems.draft1099) else
(lineitems.quantity * lineitems.labor1099) end else
case left(lineitems.item,4) when '2392' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,4) when '2391' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,4) when '3172' then (lineitems.quantity * lineitems.draft) else
case left(lineitems.item,5) when 'ECAD2' then (lineitems.quantity * lineitems.draft) else
(lineitems.quantity * lineitems.labor) end end end end end end end end as labor,
(lineitems.quantity * lineitems.vehicle) as Vehicle,
(activities.meals + activities.lodging) as PerDiem,
(employees.state) as FState, (states.state) as TState
from jobs
inner join activities on jobs.jobid = activities.jobid
left outer join employees on activities.employeeid = employees.employeeid
left outer join lineitems on activities.activityid = lineitems.activityid
inner join states on jobs.billingstateid = states.stateid
where (activities.weekending = @Weekending or activities.transferdate = @Transfer or jobs.transferdate = @Transfer)
and jobs.billingstateid <> employees.stateid and lineitems.quantity <> null
GO
Can anyone help tell me why this happens or has anyone ever experienced this before?
Thank you in advance!!!!!!
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Jul 23, 2005
Hi all,I have a sql puzzle (which I've solved) but seems very unwieldy. Isthere a more efficient way of doing this?It reads like so:SELECT a.*FROM axindex a INNER JOINaxindex b ON a.id4 = b.id4 AND a.id1 = b.id1 ANDa.id5 = b.id5 AND a.conflict_type = b.conflict_type INNER JOINaxindex c ON b.id4 = c.id4 AND b.id1 = c.id1 ANDb.id5 = c.id5 AND b.conflict_type = c.conflict_type INNER JOINaxindex d ON c.id4 = d.id4 AND c.id1 = d.id1 ANDc.id5 = d.id5 AND c.conflict_type = d.conflict_typeWHERE (a.stext = 'land') AND (b.stext = 'reg') AND (c.stext ='fees') AND (a.conflict_type = 5) AND (d.stext = 'hamilton')Many thanks in advance.Sam
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Apr 12, 2007
Hi,
I managed to get things broken and I can't solve it:
Scenario:
SQL Server
--->Databases
--->TestDB
---> Users
------> dbo mapped to user1 (user1 = SQL Server user)
------> user1(database user) mapped to nothing (no SQL user)
---->Security
-------> Logins
-------> user1
Problem: I don't want SQL Server user 'user1' to be dbo but I can't remove dbo rights because it owns objects nor can I drop database user 'user1' or delete SQL Server user 'user1' because it's mapped to dbo.
I'm running in circles..
First and last time I use the auto_fix option to fix orphaned users.
At this point, the only solution to me is dropping the database.
Anyone with a better idea?
Thank you!
Best Regards,
Worf
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Jan 17, 2008
Here's a fun little puzzle that I thought up based on some rather gnarly problems I faced today. It might brighten up your morning. See if you can figure out what it does and how it does it.
How does it work? When will it fail as written (this example does not fail)? Why will it fail? How can you change it to increae its capacity?-- ptp 20080117 SQL puzzle
DECLARE @iINT
, @cVARCHAR(360)
SET @i = 90
SET @c = ''
WHILE 64 < @i
BEGIN
SET @c = Char(@i) + Space(@i - 64) + @c
SET @i = @i - 1
END
SELECT Replace(Replace(Replace(Replace(@c
, ' ', ' '), ' ', ' '), ' ', ' '), ' ', ' ')
UNION SELECT @c-PatP
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Jul 18, 2007
I've been running my simulations against our SQL Server 2005 database all day today and have been noticing a lot of deadlocking. Almost every transaction was deadlocking and retrying.
About an hour ago I started SQL Profiler and enabled trace flags using DBCC TRACEON(3605, 1204). However, even though Performance Monitor was indicating high Deadlocks/sec ratio I could not find any evidence of them in SQL Profiler or in SQL Server error log. I restarted my simulations several times, but nothing changed.
So, then a miracle happened and the last time I started my simulations all deadlocks disappeared. I did not change any queries and I am puzzled as to what could have happened. The only things I did were starting SQL Profiler and executing DBCC TRACEON commands.
Since queries and transactions did not change, could it be that they started executing (and hence releasing locks) faster because of lower network traffic at the end of the day or because the transaction log was written to disk?
Could it be anything that SQL Server 2005 does to optimize its own performance?
What else could have caused such a drastic change?
Thanks.
Alec
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Oct 11, 2007
Hi,
Can I find out the user who has executed the job?
The result of query Q1) gives this information in the message column of the output.
Q1) select * FROMMsdb..sysjobhistory
Do we have any other table or SP from this information can be captured directly?
Regards,
Ashish Johri
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Sep 26, 2007
Hi,Probable there is a simple solution for this, hopefully someone candirect me in the right direction.I have a table with a persons firstname, lastname, birthdate andaddress. However, I want to select only one person per address, namelythe eldest of all persons living on the same address.Can anyone provide me a solution?Thanks in advance.Duncan
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Jul 20, 2005
Hello -I have three feeds from sources around the world, each coming in at aseparate time.These feeds move into a large table (3GB) that is queried by managers.The feeds are loaded sequentially, and then the previous day's feedrows are deleted from the table (this is done so that the user'sapplication is never without data).The issue is that the import takes a lot of time, as do the deletes.These is hurting performance significantly. I attempted to fix theproblem by creating separate tables for each feed. I then created aview with the original table's name and used UNION ALL's. My intentionwas that as each feed came in, I'd alter the view with the new table'sname, and then truncate the older table. This met both goals ofconcurrency and import/delete speed.Unfortunately, this view seems to ignore the indexes on the underlyingtables, which devastates performance. I can't index the view, sincealtering it makes the index less useful.I'm looking for a different strategy for loading and deleting thedata, all without disruption to the applications. I'd appreciate anysuggestions....
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Aug 7, 2006
Hello folks,
I have probably a dumb newbie question but I can't find the answer anywhere.
On my Control Flow design pane I have two objects: a SQL task object and a Data flow task object. The first 'points' to the second. From my digging I believed that by indicating with the arrow from 1 to 2 that 1 would execute to finish before 2 was started.
My SQL taks is to truncate a table to receive the new data coming from the data flow task object. Instead 2 executes first and then 1. You can imagine producing an empty table was not my goal for this package.
Can anybody give me a clue?
Thanks....
Jim
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Mar 31, 2004
Hello SQL Gurus,
I want to dynamically add a column to a select statement who must contain the line number.
Example :
Some table has 3 columns (id,field1,field2)
SELECT top 3 *,[lineNumber] as lineOrder FROM someTable
must produce
id | field1 | field 2 | lineOrder
-----------------------------------
1 abc def 1
23 def ghi 2
7 ghi jkl 3
and so on... Possible ?
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Nov 30, 2005
I have a view based on few tables okay
I have a query that gives me document details of various revisions
Now i also get the latest rev of those if i use a MAX() in my Query
Now a case where i have say
Docu Numb - Revi - Received Date
Document1 - rev0 - 10/2004
Document1 - rev1 - 11/2004
Document1 - rev2 - 12/2004
Document1 - rev3 - 01/2005
Document1 - rev4 - 02/2005
Document1 - rev5 - 03/2005
Document1 - rev6 - 04/2005
Document1 - rev7 - 05/2005
If i query for latest it gives Document1 - rev7
And if i filter for a month of 12/2004
If i query for latest it should give Document1 - rev2
Now i need to get a filter with latest as rev2,
plus i also need as a indication of actual latest as rev 7
using a query
How do i do that ...
Coz when i use filter for a month and Max then it
does not consider rev7 for that filter and skip the record
and if i try to filter only as per month .. i get a wrong info
as latest rev2 which is not a true info as per database records.
May i possibly get both ... filtered info as per specific month and
also a rev info as what is the latest for a spec document.
Just i need to know is that possible .. in SQl using a query
Any more info needed please mail me on
neeraj.jariwala@gmail.com
Life is beautiful ... When you smile ...
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Jul 23, 2007
Let me try to put this down in words...
If I log into the SQL server with my credentials and connect to SSIS through SQL Management Studio, I'm able to execute my test SSIS package successfully.
If I go to my machine and try to connect to SSIS "Integration Services..." I get "Access Denied" message.
If I execute the same package via DTEXECUI, the package errors out also.
My account is member of the group "Security_IT_Data", this group has sysadmin privileges on the SQL Server level.
The account used to run the SSIS Service is part of the Local Admin group on the box and also a sysadmin on the SQL Server.
What am I missing?
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Jul 20, 2005
I have the following data (very simplified version)TransactionId Agent_Code------------- ----------191462 95328C205427 000024C205427 75547CAgent Code 75547C is a corporate agent. The others are not. I have alist of corporate codes so I can query against it, BUT what I want todo is...Return a unique TransactionId and max of the AgentCode, but if theAgent is a corporate agent, I need to return max of the corporate agentcodes. We can have multiple agents against the transaction andsometimes have a mix of corporate and none corporate agents. What weneed to do is see the corporate adviser if there is one. I only want 1record per TransactionId.We derive more data (sales hierarchy) from this, so are not interestedin anything other than the maximum, but need to know if it wascorporate which therefore gives me a different hierarchy later.Ideally I want to do this in a view and not use an SP. I can then usethis in my main view. If I have to resort to an SP, then so be it, butI would appreciate any helpful comments (or even better, the answer)ThanksRyan
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Jul 18, 2003
Hi:
in sp_add_jobschedule
@freq_type = 8 for weekly @freq_interval = 1 for Sunday.
I need to script to create a job which will run every Sunday 6 pm, to backup one prod database to a new backup device. EX. database name is DBTest, and the 7/20/2003 (Sunday) running result should be backup_DBTest_2003_07_20.bak.
and next Sunday's should be backup_DBTest_2003_07_27.bak.
(if this way, the backup device will be created at the begining of the job running...)
this way the backup would not be overwritten. Is there a way to dynamically generate 54 weeks job script from this coming Sunday?
Or to make the backup result as backup_DBTest_2003_week27.bak, backup_DBTest_2003_week28.bak....
thanks
David
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Nov 21, 2003
SQL 2000 pricing and licensing is quite confusing, and even more pain including the upgrading pricing from sql6.5/sql7.0.
I got very clear Windows2000 pricing and upgrading from one Microsoft web address. But just could not find a ONE Microsoft web sit explicitely describe the $ pricing for each of SQL2000 edition (per processor vs. CAL..., including upgrading from SQL 6.5, SQL 7.0). May be I missed that site?
Thanks
David
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Mar 16, 2007
Guys,
We have MSSQL 2000 Server instance installed and working well on Windows 2003 Server machine [IBM X series-366] with 16GB RAM, 3.67GHZ cpu power, and 400GB hard disk space.
We further created an identical server instance on a new machine. More specifically, on Windows 2003 Server machine [Intel (R) Xeon (TM)] with 16GB RAM, 3.67GHZ cpu power, and 400GB hard disk space, we installed MSSQL 2000 Server and copied over all the dbs, applications ...
We were expecting same or similar performance (since processor speed, ram, hd, server and database configurations are all the same, with same indexes on same tables. However, for some reason, there is a noticeable difference in performance.
More specifically, I ran Profiler for 30 minutes on both servers simultaneously [same trace parameters]. The trace file of the new server is 3 times as large as that of the old one (i.e. It looks like more items are being processed). However, the average duration of the executed stored procedures is much longer on the new server than that of the old server.
Moreover, when I run same queries on 2 servers. The query on the new server always takes longer than that on the old server. And for tables where we don't have indexes, it takes much longer.
Following advice here(http://support.microsoft.com/kb/274750/), we configured our new server (just as was our old one configured) to use 15GB of RAM. I further compared the configurations of 2 servers by executing sp_configure (with advance options). The only difference I saw was that "remote proc trans" is set to off on the new server and on on the old server. I don't think it could affect this issue though.
Furthermore, the new server appears to have many more locks, as compared to the old server. Could it be because it is processing more items?
I cannot figure what is causing the queries to be slower on the new server.
Can anyone suggest anything?
Thanks a lot
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Apr 28, 2006
the talbe row like this:
ID Name Scoe 11 Tome 20 12 Jack 30 11 Tome 40 12 Jack 10 13 John 10
My query command like this:
Select T1.Id,T1.Name,T2.mathfrom st T1right join(Select Id as Id2,Sum(Math) as Math from St group by id) T2on T1.id=t2.id2where t1.id = t2.id2
While the reuslt is :
Id Name Score
11 Tom 60
11 Tom 60
12 Jake 40
12 Jack 40
13 John 10
I am wonder :the T1 gives a table with six rows, the T2 gives a table with three rows, and I use RIGHT JOIN to connect the two table,the result should be a table with only three rows.I tried INNER JOIN, the result is same.
but why ? please help me !
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Mar 29, 2007
Guys,
I am a bit puzzled. Our database backup grew from the usual size of ~27GB to ~40GB, all of a sudden. Nothing special happened in the last few days - nothing major to cause such increase.
I found out about this, because we suddenly had the backups failing, and when I explored, I saw that this was due to the lack of space on the hard-disk.
I do know that we need additional hard disk space. In the meantime, however, I'd like to be able to identify what exactly could cause such growth.
As far as I understand, for the backup to grow, the database needs to grow in a similar proportion. My only theory is that when the backup failed a few times, each time, somehow, it resulted in the database growth. Does this make any sense?
Another clue is that the backup job, which usually runs ~ 30 minutes has been running for 6 hours already, the file has grown to 40GB, and the backup job is still running ...
What is the best way for me to explore what exactly happened? Are there some system tables containing history of table counts or something - so that I can see who grew when and by how much?
I ran a query to see which objects were added in the past few days - that did not give me any clues - all looks normal.
Any ideas/suggestions?
Thanks a lot
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Oct 13, 2007
Recently I began to use SQL 2005. But yesterday I found a puzzle about data type.
I use this script to create a table:
CREATE TABLE [dbo].[InvoiceMaster](
......
[InvoiceMemo] [varchar](max) NULL,
......
)
But when I run this cmd : exec sp_columns InvoiceMaster. I find the type_name of this column changed to "text".
Can anybody tell me why?
Thanks in advance!
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Feb 21, 2008
Here's a nice puzzle for all you masochistic programmers LOL.
Actually, it's just something that's been giving me problems and I know this forum has some amazing programmers who will probably find my problem to be easy.
I'm using 2005.
Simply put...
Here's the data:
ID Start End X
123 10 15 a
123 9 10 b
123 11 18 d
123 14 16 z
123 19 21 x
234 16 18 bb
I'd like to roll up overlapping start and end numbers into one set.
So here would be the output:
ID Start End [Ttl X]
123 9 18 4
123 19 21 1
234 16 18 1
The way I'm thinking of attacking this is maybe a combination of RowNumber & a CTE of some sort.
Please no loops or cursors, or extra tables.
Any ideas guys/gals?
Thanks a mil,
Denvas
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Oct 14, 2006
A little puzzle with this Error - Status and PropertyType fields do not allow nulls while other columns do ( there are about 20 columns in original expression but left out for simplicity - these are created the same way ). Any ideas how to solve it?
[Conditional Split Filter Changes [813]] Error: The expression
"LOOK_Status != Status || LOOK_PropertyType != PropertyType
|| (LOOK_OfficeName != OfficeName || ISNULL(LOOK_OfficeName) != ISNULL(OfficeName))
|| (LOOK_OfficeID != OfficeID || ISNULL(LOOK_OfficeID) != ISNULL(OfficeID)) "
on "output "Listing Changed" (885)" evaluated to NULL, but the "component "Conditional Split Filter Changes" (813)" requires a Boolean results.
(My wish for next version is to have better expression editor and be able to see the output for those in dataflow transforms with lets say sample 200 rows)
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Oct 25, 2006
Hi everybody,I need to understand how concurrency excatly
work in asp.net. For example, I'm confused what happens if two users at
the same time try to access the same record in a table or even the same
variable. Do ASP.NET handle this , I mean by locking one user and
letting the other to have access OR it's up to the programmer to write
some code to lock shared resources such as database , objects and
variables?If it's up to the programmer to do this task, I appreciate if you can show me an example that clarifies that.Thank you
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Jul 23, 2005
Following on from a thread I started about "concurrency" (real-time-ishsystem), I thought I would play about to see if I could easily adapt my datamodel to take account of potential multi-user write conflicts. So, I wouldappreciate you checking my logic/reasoning to see if this kind of thingwill work. Below I have a stored procedure that will simply delete a givenrecord from a given table. I have appended a "_Written" counter to thecolumns of the table. Every time the record is written, the counter isincremented. Clients store the current _Written count in their objects andpass this in to any write procedure executed.The procedure explicitly checks the _Written count within the transaction tosee if it agress with the written count passed in by the client. If it doesnot, the client throws an error. Note I am explicitly checking the_Written count precisely so I can determine exactly why this operation mightfail, rather than checking @@ROWCOUNT after an update.Thanks.RobinCREATE PROCEDURE dbo.proc_DS_Remove_DataSet@_In_ID INTEGER,@_In_Written INTEGERASDECLARE @Error INTEGERDECLARE @WRITTEN INTEGERBEGIN TRANSACTIONSET @Error = @@ERRORIF @Error = 0BEGINSELECT @WRITTEN = _Written FROM MyTable WHERE ID = @_In_IDSET @Error = @@ERRORIF @WRITTEN <> @_In_WrittenBEGINRAISERROR ('10', 16, 1)SET @Error = @@ERRORENDENDIF @Error = 0BEGINDELETE FROM MyTable WHERE ID = @_In_IDSET @Error = @@ERRORENDIF @Error = 0COMMIT TRANSACTIONELSEROLLBACK TRANSACTIONRETURN @Error
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May 27, 2007
Do single commands (or stored procedures) execute concurrently, or they are executed one by one. How do you perform a lock during the execution of a command (or stored procedure).
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Jun 20, 2006
I have a user object that is stored in the session for each user but what if an administrator updates a certain user and I want to reflect the update to the user if they are logged in?One possible way of solving this is:Each time the user goes to a page, check the user table and compare the timestamp. That would mean if 30 users refresh the page..the db would hit 30 times lol. I don't think that would scale very well.Any ideas on how to solve this?
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Aug 4, 2006
I have a table where I count how many emails of a given type are sent out each day. This incrementing is wrapped in a sproc that either inserts a new row, or updates the existing row. The column that counts the value is named Count of type INT.
Below is the sproc, seems like a straightforward thing. However, I'm seeing email counts higher than they should be when there's a high number of concurrent executions of the sproc. I'm pretty sure it's not a problem in the calling code, so I'm wondering about the UPDATE statement, since it updates a column based on the value of the column. I would think this should work since it's wrapped in a SERIALIZABLE transaction, anybody have further insight?
SQL Server 2005 by the way.
Sean
CREATE PROCEDURE [dbo].[IncrementEmailCounter]( @siteId SMALLINT, @messageType VARCHAR(20), @day SMALLDATETIME) ASBEGIN SET NOCOUNT ON;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE BEGIN TRANSACTION
IF (SELECT COUNT(*) FROM EmailCount WHERE SiteId = @siteId AND MessageType = @messageType AND [Day] = @day) = 0 INSERT INTO EmailCount (SiteId, MessageType, [Day], [Count]) VALUES (@siteId, @messageType, @day, 1) ELSE UPDATE EmailCount SET [Count] = [Count] + 1 WHERE SiteId = @siteId AND MessageType = @messageType AND [Day] = @day
COMMIT TRANSACTION SET TRANSACTION ISOLATION LEVEL READ COMMITTEDEND
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Feb 17, 2007
I'm wondering whether the following code would work if users are RAPIDLY registering (assumption) WITH the same username.public bool UsernamExists(string username)
{
string sql = "SELECT true FROM [users] WEHRE username = @username;";
return Convert.ToBoolean(comm.ExecuteScalar());
}
public bool Signup(User user)
{
bool usernameExists = UsernameExists(user.Username);
if( usernameExists ) return false;
//update or insert sql for user etc blah blah
} If two users try to signup AT THE VERY SAME TIME (DOWN TO THE NANOSECOND), would this technique work? Do I have to wrap it in a transaction, stored procedure?? Thanks.
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Jun 1, 2007
Hi,I'm trying to implement Optimistic Concurrency in asp 2 but so far it has caused me nothing but problems.First, when doing an UPDATE I tried to use the primary key & a timestamp field which I had in SQL Express.. VS 2005 generated the stored procedures fine however when it came to the actual updating I think there was a problem with the conversion of the timestamp field when it was being stored in a text box (in a FormView control). So.. as a result that failed. And also I checked sooo many places online and haven't been able to find any examples of code where a timestamp was used with success in asp2.Next, I got ride of the timestamp type (in SQL Express database) and used a datetime and then.. I just implemented Optimistic Concurrency by passing in ALL the values (ie all the original values) like is proposed http://www.asp.net/learn/dataaccess/tutorial21vb.aspx?tabid=63 . This... works however I really do not want to have to pass in ALL these values (ie original and new).Ideally I would like to be able to use the primary key & the datetime field to handle the Optimistic Concurrency checks where only the original values of both those fields are passed back into the stored procedure. Now.. I tried this as well, but I kept getting an error that suggests that (for some reason) the FormView or DataSource is passing ALL the values (original & new) into the dataset as opposed to only the original primary key & datetime fields & the new set of values.Can ANYONE offer any help? I really would like not to have to pass in all these values.Thanks in advance!
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