Local Vs. Global Uniqueness And General Tagability
Jun 17, 2008
So, I have this idea of a database design I was hoping to get some input on.
I usually go through the process of creating a separate column for identity, like an auto-increment integer which serves as a context specific ID that easily can be passed around. However one of the short-comings I've come to realize is that the integer is just that, unique to the context and requires context information to make sense.
I'm pounding the idea of creating a separate table whose sole purpose is to provide global (database wide) unique IDs. As such each row in a table can still have an ID but instead of being tied to a specific context it will always make sense within the application. A foreign key constraint can ensure that and a relation.
Now, with a global ID which I can create FKs to, I don't have to create a separate table for relations between entities and can have relations through these global IDs and I think that's a good thing because if there are many relations between many entities they don't have to be defined more than once. There is also a single "hub" where all relations fit which will allow me to access most information through some relatively simple joins.
My concerns are performance and Linq to SQL implication. I'm worried that Linq to SQL might start pulling an excessive amount of data and I'm worried that the practicality of such a design might hurt the long running of the application development process.
But I'm surprisingly interested in what it could mean for a more ubiquitous view of data and tagging. Basically a way of any data to have relations to any other data through this yet simple design decision.
If you think this is a good idea or see no particular problem with, please let me know! If you think there's problems with my idea, please motivate your critic but do tell me what I should look out for, or if you know of any better approach to my idea of being able to look at the data through some more common mechanism (which applies to all tables and the entire database mostly from a programming perspective).
Hello, In NT MS suggests putting global groups into local groups and then assigning object permissions to those local groups in NTFS. I was wondering if this pattern should be followed in SQL server when assigning permissions to integrated login accounts. Is it better to use global groups or local groups?
Can anyone tell me or post a link that says how many global temptables can exist SQL Server 2000? Also, is there a limit to thenumber of local temp tables that can exist?Thanks,Billy
Hi,I am new to SQL. Please bear with me and allow me to ask a dumbquestion.I am debugging a stored procedure (written in Trans-SQL), and I foundthat the SQL analyzer that I use doesn't have a debugger. All I cando it is execute a block of code and see what is going on in aninteraction seesion of the SQL analyzer. I would need to declare somevariable to hold values of the previous query in the interactivesession.I understand that this can be easily done in a stored procedure viathe Declare command (e.g., Delcare @order_no int). Is similarfunctionality exists in an interaction session of the SQL analyzer?If so, what is the command. Please advise.Thank you very much for the help.Alex
I am stuck in a bit of a conundrum for quite a while now, and I hope someone here will help me figure this one out.
So, first things first: let me explain what I need to do. I am designing a web application that will allow users to consult info available in a SQL2000 database. The user will enter the search criterea, and hopefully the web page will show matching results.
The problem is the results shown aren't available per se in the DB, I need to process the data a bit. I decided to do so on the SQL Server side, though the use of cursors. So, when a user defines his search criteria, I run a stored procedure that begins by building a dynamic sql query and creating a cursor for it. I used a global cursor in order to do so. It looked something like this:
SET @sqlQuery = ... (build the dinamic sql query)
SET @cursorQuery = 'DECLARE myCursor CURSOR GLOBAL FAST_FORWARD FOR ' + @sqlQuery
EXEC @cursorQuery
OPEN myCursor
FETCH NEXT FROM myCursor INTO ...
CLOSE myCursor
DEALLOCATE myCursor
This works fine, if there's only one instance of the stored procedure running at a time. Should another user connect to the site and run a search while someone's at it, it'll fail due to the atempt to create a cursor with the same name.
My first thought was to make the cursor name unique, which led me to:
...
SET @cursorName = 'myCursor' + @uniqueUserID
SET @cursorQuery = 'DECLARE '+ @cursorName + 'CURSOR FAST_FORWARD FOR ' + @sqlQuery
EXEC @cursorQuery
...
The problem with this is that I can't do a FETCH NEXT FROM @cursorName since @cursorName is a char variable holding the cursor name, and not a cursor variable. So to enforce this unique name method the only option I have is to keep creating dynamic sql queries and exucting them. And this makes the sp a bitch to develop and maintain, and I'm guessing it doesn't make it very performant.
So I moved on to my second idea: local cursor variables. The problem with this is that if I create a local cursor variable by executing a dynamic query, I can't extract it from the EXEC (or sp_executesql) context, as it offers no output variable.
I guess my concrete questions are:
Is it possible to execute a dynamic sql query and extract a (cursor) variable from it?Is it possible to populate a local cursor variable with a global cursor, by providing the global cursor's name?Can I create a local cursor variable for a dynamic sql query? How?
Anybody sees another way arround this?Thanks in advance,
Hi, I have compact sql databases which will be local on multiple users devices. Due to space constraints, for one of the tables i have had to use auto incrementing integer which works fine for the local database but i would like to merge all of the users databases into a global database. The table format can be seen below:
Code SnippetCREATE TABLE Players ( ID UNIQUEIDENTIFIER NOT NULL PRIMARY KEY, FirstName NVARCHAR(32), LastName NVARCHAR(32) );
The Players table will merge fine as GUIDs are used. However, how will the sync capabilities of compact SQL handle the sessions table? When it pushes the local data to the remote database will it change the Sessions.ID column to a unique field (as no doubt lots of people will have 1, 2, 3 in their local databases and the global database must have a unique ID), and then transfer this changed ID back to the local database? Furthermore, if it changes the Sessions.ID column during the merge it will also need to update the SessionDetail.SessionID foreign key to maintain referential integrity, is this also handled?
So my question is, how much of this sync and data merge is automated and are there any good examples or pointers for my scenario? I cannot reasonably use a GUID for Session.ID as there will be lots of SessionDetail entries and the size would be far too much.
Looking at BOL for temp tables help, I discover that a local temp table (I want to only have life within my stored proc) SHOULD be visible to all (child) stored procs called by the papa stored proc.
However, the following code works just peachy when I use a GLOBAL temp table (i.e., ##MyTempTbl) but fails when I use a local temp table (i.e., #MyTempTable). Through trial and error, and careful weeding efforts, I know that the error I get on the local version is coming from the xp_sendmail call. The error I get is: ODBC error 208 (42S02) Invalid object name '#MyTempTbl'.
Here is the code that works:SET NOCOUNT ON
CREATE TABLE ##MyTempTbl (SeqNo int identity, MyWords varchar(1000)) INSERT ##MyTempTbl values ('Put your long message here.') INSERT ##MyTempTbl values ('Put your second long message here.') INSERT ##MyTempTbl values ('put your really, really LONG message (yeah, every guy says his message is the longest...whatever!') DECLARE @cmd varchar(256) DECLARE @LargestEventSize int DECLARE @Width int, @Msg varchar(128) SELECT @LargestEventSize = Max(Len(MyWords)) FROM ##MyTempTbl
SET @cmd = 'SELECT Cast(MyWords AS varchar(' + CONVERT(varchar(5), @LargestEventSize) + ')) FROM ##MyTempTbl order by SeqNo' SET @Width = @LargestEventSize + 1 SET @Msg = 'Here is the junk you asked about' + CHAR(13) + '----------------------------' EXECUTE Master.dbo.xp_sendmail 'YoMama@WhoKnows.com', @query = @cmd, @no_header= 'TRUE', @width = @Width, @dbuse = 'MyDB', @subject='none of your darn business', @message= @Msg DROP TABLE ##MyTempTbl
The only thing I change to make it fail is the table name, change it from ##MyTempTbl to #MyTempTbl, and it dashes the email hopes of the stored procedure upon the jagged rocks of electronic despair.
Any insight anyone? Or is BOL just full of...well..."stuff"?
My replication is not working. I was able to create a transactional replication successfully. However, when i tried starting the agent on the snapshot, it wouldn't work. I figure that it was because my agent service login is different from that of the subscriber. my publisher and distributor is on local user whereas my subsciber sql services use our global login.
I have one domoain in the forest. The domain level is set to Windows 2000 native mode and forest level is set to mixed mode. My SQL server 2005 server joined to this domain. I added a brand new domain local group and add a normal user account to this domain local group. I login to the SQL server 2005 server and make a query "SELECT * FROM sys.login_token". I cannot see my domain local group in sys.login_token. However, if I add my account to a global group, I can see it there.
Then, I setup another forest. This time, I have domain level set to Windows 2003 mode and forest level is set to Windows 2003 native mode. I do the same testing. This time, I can see my domain local group in sys.login_token.
Why does SQL server 2005 has this limitation? Is it a bug?
When I select a fieldname in a db as a primary key this will keep the uniqueness of that fieldname, but how is that work when I select 2 fieldnames (in Enterprise Manager) and click on the Key it will mark them as my primary key, but I can insert duplicates values in either fieldname.
this violates the constraint if i give the two teams on the same date..how to give the condition such that it checks for the violation of condition if the team names are interchanged.. for eg
if i give the values as Insert Into Games values('chelsea',1,'arsenal',2,'17-1-2000'); and Insert Into Games values('arsenal',1,'chelsea',2,'17-1-2000');
the above should violate the constraint ..how to do it
My company is upgrading one of our products; this involves some data migration and a question about existing indexes with uniqueness constraints has been raised. Here is the issue:
We have a database table with two particular columns that that we index with a uniqueness constraint. My question is: is the uniqueness constraint case sensitive?
For instance, if I have a database that is using a collation of SQL_Latin1_General_CP1_CS_AS. (case sensitive) and I insert data in these two columns as follows:
test col2test
Test col2test
would this uniqueness constraint be violated even though I'm using a case sensitive collation? I've done tests on this issue and I can't seem to insert this 2nd column; I'm just wanting to be certain that this is the case 100% of the time.
Hi, Can anyone tell me the order in which uniqueness constraints on indexes are enforced vs. when triggers are executed ? I have a unique constraint on an index and a trigger on the column on which the same index has been created. When a row is inserted, the trigger checks if the value for that column already exists in the table - if not, it inserts the row as is, else it gets the max() val of the column (based on another key column) and increments it by one, then does the insert. Creating an index across the two works fine, but if I set the Unique Values property for the index, subsequent inserts bomb out - yet there aren't any duplicates in the final table, as the trigger ensures this. Anyone got any ideas on this? My deduction is that the uniqueness constraint gets enforced before the trigger gets executed, but at the same time this *seems* illogical, as the row has not been inserted into the table at the point where the trigger is executed.
OK - maybe my Google-fu is off today but I'm trying to find out if using a sequence table will provide values that are as unique as the GUID is supposed to be.The reason is that I'm building a DW from the ground up (they won't let me expense my booze which I think is grossly unfair ) and rather than using GUID it ~seems~ like a sequence table would give better results. My concern is that the values won't be unique across tables.
Hi,First of all my apologies if you have seen this mail already but I amre-sending as there were some initial problems.This query is related to defining indexes to be unique or not andconsequences thereof.Some documented facts that I am aware of include1. Defining uniqueness allows optimiser to create optimal plans egselect based on keys in such an index allows the optimiser to determineat most only one row will be returned2. Defining uniqueness ensures that rule (business/Primary key) isenforced, regradless of how the data is entered.We have many cases where non unique indexes are defined. The approach todate has been that even though we are aware of some of the benefitsoffered by defining uniqueness , we have chosen not to add keys to nonunique indexes such that they become unique. The primary reason for thiswas that we did not want to make the keys comprising the indexesunnecessarily large and therefore ensuing consequences when DMLstatements are performed.However, I have concerns that having highly duplicate indexes can haveperformance impacts , including deadlocking. I am also aware Sybase usedto store duplicate values in overflow pages and therefore there wereperformance consequences. Could SQL 2000 have the same behaviour ?Thanking you in advancePuvendran*** Sent via Developersdex http://www.developersdex.com ***Don't just participate in USENET...get rewarded for it!
I want to make sure that usernames and folder names (that are stored in the database) are all unique when created by the admin through an admin control panel.
How would I code and use an Index to make sure that the 2 columns are unique?
I've looked at examples on the net but nothing is telling me how I can create an index through Enterprise Manager? Thanks
I want to make sure that usernames and folder names (that are stored in the database) are all unique when created by the admin through an admin control panel.
How would I code and use an Index to make sure that the 2 columns are unique?
I've looked at examples on the net but nothing is telling me how I can create an index through Enterprise Manager? Thanks :)
I"m trying to use a BULK INSERT command to insert data into a table from a file. There is a UNIQUE Index that is being violated and the BULK INSERT fails.
I do not want to drop or disable the index, however, i also do not want to load 'duplicate' records so i keep the CHECK_CONSTRAINTS parameter.
Is there a way to have the duplicate records outputed to the ERRORFILE ?
Is there a system table column to query to determine whether an index is defined as unique in SQL Server 2000? It is easy to find this info in SQL Server 2005, but I don't see a valid column for this on dbo.sysindexes.
All- I have what i'm sure is a question with a simple answer: Supposing I want to modify the select command below to force the display of records with only unique combinations of the two fields person_id and act_session_id (bolded). How would I do this. Note that neither is a key field. (Key field headcount_id was added for completeness.) Thanks! SELECT hd.headcount_id, hd.person_id, hd.act_session_idFROM headcount as hd
I am reading "SQL Server Query Performance Tuning Distilled",on page 104 it talks about one of the index design recommendationswhich is to choose the column that has very high selectivity of valuesinstead of a column that has very few selectivity of values.My question is if I have currently indexes on my tables that have1, 2, 3, 4, ... values only on thousands of rows, are these nonclusteredindexes pretty much useless indexes that I should get rid of?And I know that pretty much the number of selectivity values willalways remain very low.Thank you
We have a 64-bit VM server running SQL Server 2005. The SQL Server on this particular VM server has 6 local instances installed. On the Management Studio logon screen I can type the full name of the local instance and connect to it, however if I press the drop down in the Server name field, choose Browse and select the Local Servers tab there is nothing listed under Database Engines.
Any idea why the 6 local instances don't show up under Database Engines? This is preventing me from installing a vendor application because their installer looks for local SQL Server instances on this server, but if SQL Server won't even show the local instances then the installer doesn't see them either.
I am facing a problem in connecting to the local database with server name as (local).
I have installed SQL Server 2005 in my machine. When I try to connect to the SQL server with the server name as SUNILKUMAR I am able to connect but when I try to connect to the same server with the server name as (local) I am not able to connect. SUNILKUMAR is my machine name and SQL server is running locally.
if anyone can help me what is the problem in this case it is highly appriciated.
My goal is to develop the system on a windows application and pda
There is a central server which will create a publication called inventory
The laptops which host the windows application will be subscribers to the central server using merge replication
The client now wants the PDA using SQL Mobile to synchronize with the local subscirber database on the laptop using active sync. They dont want to do it via WIFI to the IIS Server at the central server
I have been reading for days and I am still unsure whether this is possible to do.
I know Appforge provide a conduit for palm to access synchronization but not local sql databases
Being a very novice SQL Server administrator, I need to ask the experts a question.
How do I go about moving a database from 1 drive to another? The source drive (C is local to the server, but the target drive (E is on a Storage Area Network (SAN), although it is still a local drive for the server. I want to move the database from C: to E:. Can someone provide me with instructions?
This is my first time to deploy an asp.net2 web site. Everything is working fine on my local computer but when i published the web site on a remote computer i get the error "Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed" (only in pages that try to access the database) Help pleaseee
The following is my code. What I am trying to do is find all the students a teacher as assessed during a give time. Then find out which assessment was done the most recently. After that I will then be aggregating those results. I have never written any pl/sql or T-SQL... heck I don't even know what to call it!The first sql command is doing what I want it to. I can only assume the cursor is working correctly. Any help would be greatly appreciated.BryanALTER procedure Domain@UserID numeric,@StartDate datetime,@EndDate datetime AS-- Variable DeclerationDECLARE @SessionID varchar(1000)DECLARE @EachSessionID numeric --Cursor to find all Children that the teacher has assessed for the given timeDECLARE ChildID_cursor CURSORFORSELECT DISTINCT childID FROM capsessionWHERE userid = @UserIDAND sessiondate BETWEEN @StartDate AND @EndDate-- looping through all Children to find there most recent assessment.OPEN ChildID_cursorDECLARE @ChildID numeric FETCH NEXT FROM ChildID_cursor INTO @ChildIDWHILE (@@FETCH_STATUS <> -1)BEGIN IF (@@FETCH_STATUS <> -2) BEGIN DECLARE SessionID_cursor CURSOR FOR SELECT TOP 1 CAPSessionID FROM CapSession WHERE (ChildID = @ChildID) AND (SessionDate BETWEEN @StartDate AND @EndDate) ORDER BY SessionDate DESC END FETCH NEXT FROM ChildID_cursor INTO @ChildIDENDCLOSE ChildID_cursor OPEN SessionID_cursorFETCH NEXT FROM SessionID_cursor into @EachSessionID SET @SessionID = ''WHILE (@@FETCH_STATUS <> -1)BEGIN IF (@@FETCH_STATUS <> -2) BEGIN SET @SessionID = @SessionID + @EachSessionID+ ',' END FETCH NEXT FROM ChildID_cursor INTO @ChildIDENDCLOSE SessionID_cursorRETURN @EachSessionID
Hi, I wanna know if one has to undergo the 'sql video tutorials' on this website before trying to understand data access tutorials, again on this site. Are the two related by any chance. Also I am not able to find the customer database files he has created in tutorial # 5, dumb to ask, but what to do?,...so anyone willing to shed light!!!
as you might have seen, I'm a total newbie to this Site and M$ SQL. I browsed the forum to see if there are already matching answers to my question, with no success.
My question: As a MySQL & PHP user I ask myself if there is a possibility to use M$ SQL the way I use MySQL and PHP!? Is there a way to generate dynamic websites with M$ SQL 2000 and a webserver running PHP sources? A brief yes or no would really help me, if you have any links or resources on this topic, I'd be glad to hear about it.
I get the error "General SQL Error" when reading or writing to a memo field in Sql Server through a frontend build in Delphi 4. I'm Using the latest BDE. I have recently installed this onto a NT enviroment in the same manner as my own enviroment but get the error message above.
On my own enviroment and a friends enviroment I do not get any errors.
Can someone please give me some help on this or a direction to run in ?
Hi, folks. I've a production SQL machine with more than 20 users making transactions 24 hrs in 6 days a week. I've only Sunday for maintenance. The server has fixed 2 GB RAM allocation for SQL. Is it good to Restart SQL ( or machine) to clear the Buffer-Cache( or is it good to keep the cache) .... :rolleyes:
