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• Using views as a data interface between modules in a database

  - by Stefan

  Hello, I am working on the database layout of a straighforward small database in Mysql. We want to modularize this system in order to have more flexiblity for different implementations we are going to make. Now, the idea was to have one module in the database (simple a group of tables with constraints between them) pass its data to the next module via views. In this way, changes in one module would not affect the other ones, as we can make sure in the view that the right data is present there at any time, although the underlying structure of tables might be different. The structure of the App handling the database would likewise be modularized. Is this something that is sometimes done? On a technical side, as I understand views can't have primary keys - how would I then adress such a view? What other issues should be considered?

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• Best Language for the job? Database | C++, .NET, Java

  - by Randy E

  Ok, quick overview. I'm pretty brand new to software design. I have experience reading and editing/customizing PHP things for online scripts/software; Such as CMS, Wordpress, some forum solutions. I'm about to begin my degree in Software Design, the school I'm going to will allow us to kind of focus on an area, C++, Java, or .NET. I've played around a little with VB over the past week, mostly just trying to get a slight feel for it, however nothing extensive. I've been through Herbert Schildt's "C++, A Beginner's Guide." but I was mainly reading it, not doing anything with it beyond a couple basic Console Apps (and getting frustrated with auto-close :/ ). Now, where I decide to focus more in with my degree will depend on what the best language for the job is for my first piece of software I want to develop on my own. Assume I haven't looked at any of the languages at all, please help with the following: My first piece of software will be a database program. Everything has to do with users inputting and retrieving data, and calling that data to help with another function of the software, automatically calculating billing information based on information inputted in the other portion of the program. I won't go into too many details as I'm targeting a niche that doesn't have too much competition, but the competition that is there is established. I want to offer more features, scalable solutions, and the ability to port it to an online version. Ok, basically, it is a complete case management with integrated billing for Private Investigators. I would like the case management to be able to check the Database to see if certain information has been inputted before (such as Names/SSN's), and then the billing will pull hours inputted in the case portion for investigative work, multiplying by an already inputted amount for the fee, and then calculate sales tax. I also want to provide potential clients with an easily scalable solution, that is, a basic option for start ups that costs the least amount, with no additional users, ran on one machine. A middle option with the ability to create users and place them in two groups (User or Admin), as well as adding a few additional features, ran on one machine, but this will allow it to be accessed after being mapped on a network drive. And a third option to allow the placement into 4 different groups (Investigators, Billing, Managers, Admins) and more features. And then, a couple of years after launch, a 4th option that is browser based allowing the same 4 groups to login, as well as clients (view things concerning their case, with some admin customizable objects that can be added for clients view), over the internet. The only licensing security I would like to employ right off the bat will be serial key generated after ordering online (received in an email after the successful purchase). The program will access a database stored on a server periodically to verify license. I would like it to be able to check to make sure it's the most updated version and automatically update if not.

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• Creating an SQL variable character column > 255 characters supporting multiple databases

  - by Piers

  I have an application that stores data through an ODBC data source of the user's choosing. So far it has worked well on a range of database systems (e.g. JET, Oracle, SQL Server), as the SQL syntax is fairly simple. Now I am running into a problem where I need to store more than 255 characters in my strings. Previously I created the table using column type VARCHAR (255). Now if I try to create a table using, e.g. VARCHAR (512) then it falls over on Access databases. I know that I can use the MEMO type for Access, but this is non-standard SQL and will thus likely fail on other database systems (e.g. Oracle). Is there any widely supported SQL standard for creating text columns wider than 255 characters, or do I need to find another solution? The alternatives seem to me to be: 1) Profile the database system and customise the SQL CREATE TABLE command based on the database system. I don't like this as it defeats the purpose of using ODBC. 2) Add extra columns of 255 chars as required (e.g. LONGSTRING1, LONGSTRING2, ...) and concatenate after reading. I don't like this because it means the number of columns can vary between tables and it complicates read/write. Are there any other viable alternatives to these two options? Or is it possible to have an SQL compliant CREATE TABLE command supported by the majority of database vendors, that supports strings longer than 255 chars?

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• How do you handle objects that need custom behavior, and need to exist as an entity in the database?

  - by Scott Whitlock

  For a simple example, assume your application sends out notifications to users when various events happen. So in the database I might have the following tables: TABLE Event EventId uniqueidentifier EventName varchar TABLE User UserId uniqueidentifier Name varchar TABLE EventSubscription EventUserId EventId UserId The events themselves are generated by the program. So there are hard-coded points in the application where an event instance is generated, and it needs to notify all the subscribed users. So, the application itself doesn't edit the Event table, except during initial installation, and during an update where a new Event might be created. At some point, when an event is generated, the application needs to lookup the Event and get a list of Users. What's the best way to link the event in the source code to the event in the database? Option 1: Store the EventName in the program as a fixed constant, and look it up by name. Option 2: Store the EventId in the program as a static Guid, and look it up by ID. Extra Credit In other similar circumstances I may want to include custom behavior with the event type. That is, I'll want subclasses of my Event entity class with different behaviors, and when I lookup an event, I want it to return an instance of my subclass. For instance: class Event { public Guid Id { get; } public Guid EventName { get; } public ReadOnlyCollection<EventSubscription> EventSubscriptions { get; } public void NotifySubscribers() { foreach(var eventSubscription in EventSubscriptions) { eventSubscription.Notify(); } this.OnSubscribersNotified(); } public virtual void OnSubscribersNotified() {} } class WakingEvent : Event { private readonly IWaker waker; public WakingEvent(IWaker waker) { if(waker == null) throw new ArgumentNullException("waker"); this.waker = waker; } public override void OnSubscribersNotified() { this.waker.Wake(); base.OnSubscribersNotified(); } } So, that means I need to map WakingEvent to whatever key I'm using to look it up in the database. Let's say that's the EventId. Where do I store this relationship? Does it go in the event repository class? Should the WakingEvent know declare its own ID in a static member or method? ...and then, is this all backwards? If all events have a subclass, then instead of retrieving events by ID, should I be asking my repository for the WakingEvent like this: public T GetEvent<T>() where T : Event { ... // what goes here? ... } I can't be the first one to tackle this. What's the best practice?

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• Oracle ALTER DATABASE OPEN

  - by Tom

  Hi everyone, Im having some trouble with an oracle database. Every time i try to connect, i get this message. ORA-01033: ORACLE initialization or shutdown in progress I searched the web, and found that the solution is to execute an alter database open command, but what I dont understand is where should i execute if, since I cant connect to the database. Am I missing something? Thanks in advance

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• Can you add identity to existing column in sql server 2008?

  - by bmutch

  In all my searching I see that you essentially have to copy the existing table to a new table to chance to identity column for pre-2008, does this apply to 2008 also? thanks. most concise solution I have found so far: CREATE TABLE Test ( id int identity(1,1), somecolumn varchar(10) ); INSERT INTO Test VALUES ('Hello'); INSERT INTO Test VALUES ('World'); -- copy the table. use same schema, but no identity CREATE TABLE Test2 ( id int NOT NULL, somecolumn varchar(10) ); ALTER TABLE Test SWITCH TO Test2; -- drop the original (now empty) table DROP TABLE Test; -- rename new table to old table's name EXEC sp_rename 'Test2','Test'; -- see same records SELECT * FROM Test;

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• Cloud Database Service Latency/Performance

  - by Gcoop

  Hi All, I am running a heavy traffic site and our server is beginning to get to its limits, at the moment the entire LAMP stack is on one box (not ideal). I would like to move the database onto it's own box or onto a cloud service, but from my previous experience moving the database off the same box as the webserver increases the latency of reads quite dramatically slowing down the site. Is using a cloud service for this going to overcome this problem, because as far as I can tell its essentially the same situation (as moving it onto a separate box in my control)? In which case why is there so much popularity around cloud based database services at the moment? Are cloud based database services so quick that the latency of reads is so low that its almost like having it on the same box in the same datacentre?

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• SQL query for getting data in two fields from one column.

  - by AmiT

  I have a table [Tbl1] containing two fields. ID as int And TextValue as nvarchar(max) Suppose there are 7 records. I need a resultset that has two columns Text1 and Text2. The Text1 should have first 4 records and Text2 should have remaining 3 records. [Tbl1] ID | TextValue 1. | Apple 2. | Mango 3. | Orange 4. | Pineapple 5. | Banana 6. | Grapes 7. | Sapota Now, the result-set should have Text1 | Text2 Apple | Banana Mango | Grapes Orange | Sapota Pineapple |

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• Check for Duplicates in a Database Before Entering Data

  - by gamerzfuse

  Before Entering data into a database, I just want to check that the database doesn't have the same username in the database already. I have the username in SQL set as a key, so it can't be duplicated on that end, but I am looking at finding a more user-friendly error message then "KEY already exists". Is there are simple way to check if the variable value already exists in a row? Thanks!

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• Wordpress database migration

  - by Sean Cull

  Hi Everyone! I've looked around the Wordpress forums about this and didn't find anything so I thought I might try here. If you have a staging/dev Wordpress setup used for testing new pluging and such, how do you go about migrating the data in the staging database back to the production database? Is there a "Wordpress best practices" way to do this, or am I limited to having to manually migrate tables from one database to the other?

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• In MS SQL Server, is there a way to "atomically" increment a column being used as a counter?

  - by Dan P

  Assuming a Read Committed Snapshot transaction isolation setting, is the following statement "atomic" in the sense that you won't ever "lose" a concurrent increment? update mytable set counter = counter + 1 I would assume that in the general case, where this update statement is part of a larger transaction, that it wouldn't be. For example, I think this scenario is possible: update the counter within transaction #1 do some other stuff in transaction #1 update the counter with transaction #2 commit transaction #2 commit transaction #1 In this situation, wouldn't the counter end up only being incremented by 1? Does it make a difference if that is the only statement in a transaction? How does a site like stackoverflow handle this for its question view counter? Or is the possibility of "losing" some increments just considered acceptable?

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• Designing a database file format

  - by RoliSoft

  I would like to design my own database engine for educational purposes, for the time being. Designing a binary file format is not hard nor the question, I've done it in the past, but while designing a database file format, I have come across a very important question: How to handle the deletion of an item? So far, I've thought of the following two options: Each item will have a "deleted" bit which is set to 1 upon deletion. Pro: relatively fast. Con: potentially sensitive data will remain in the file. 0x00 out the whole item upon deletion. Pro: potentially sensitive data will be removed from the file. Con: relatively slow. Recreating the whole database. Pro: no empty blocks which makes the follow-up question void. Con: it's a really good idea to overwrite the whole 4 GB database file because a user corrected a typo. I will sell this method to Twitter ASAP! Now let's say you already have a few empty blocks in your database (deleted items). The follow-up question is how to handle the insertion of a new item? Append the item to the end of the file. Pro: fastest possible. Con: file will get huge because of all the empty blocks that remain because deleted items aren't actually deleted. Search for an empty block exactly the size of the one you're inserting. Pro: may get rid of some blocks. Con: you may end up scanning the whole file at each insert only to find out it's very unlikely to come across a perfectly fitting empty block. Find the first empty block which is equal or larger than the item you're inserting. Pro: you probably won't end up scanning the whole file, as you will find an empty block somewhere mid-way; this will keep the file size relatively low. Con: there will still be lots of leftover 0x00 bytes at the end of items which were inserted into bigger empty blocks than they are. Rigth now, I think the first deletion method and the last insertion method are probably the "best" mix, but they would still have their own small issues. Alternatively, the first insertion method and scheduled full database recreation. (Probably not a good idea when working with really large databases. Also, each small update in that method will clone the whole item to the end of the file, thus accelerating file growth at a potentially insane rate.) Unless there is a way of deleting/inserting blocks from/to the middle of the file in a file-system approved way, what's the best way to do this? More importantly, how do databases currently used in production usually handle this?

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• Weblogic 10.0: advantages with database connectivity and gotchas?

  - by Paul

  What advantages (if any) does Weblogic 10.0 provide in terms of database connectivity (to any database) over open source or commercial alternatives? Are there any Weblogic specific gotchas with using a Weblogic database connection? I'm a J2/JEE, Weblogic newbie so please excuse the simple questions.

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• Shrink database after removing extra data

  - by Sergey Osypchuk

  We have a need to fit database in 4G in order to use ms sql express edition. I started from 7G database, and found a lot of not needed records, and deleted them. After Shrink database size is 4.6G, and 748MB is free (according to database properties). However, when i execute exec sp_spaceused i am having interesting results: DatabaseName Database_size unallocation space xxxxxx 4726.50 MB 765.42 MB Reserved Data index_size unused 3899472 KB 1608776 KB 1448400 KB 842296 KB Any ideas, how can i bite at least some of this unused space? Also I know table, which occupied it. update: is it worth to try to rebuild table indexes? ALTER INDEX ALL ON Production.Product REBUILD

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• Alternative databases to use when putting IIS Logs into a database using LogParser

  - by Robin Day

  We have run some scripts that use LogParser to dump our IIS logs into a SQL Server database. We can then query this to get simple stats on hits, usage etc. It's also good when linking it to error log databases and performance counter database to compare usage with errors, etc. Having implemented this for just one system and for the last 2-3 weeks we already have a 5GB database with around 10 million records. This is making any queries to this database quite slow and will no doubt cause storage issues if we continue to log as we are. Can anyone suggest any alternative databases that we could use for this data that would be more efficient for such logs? I'd be particularly interested in any experience of Google's BigTable or Amazon's SimbleDB. Are either of these suitable for reporting queries? COUNTs, GROUP BYs, PIVOTs?

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• How can I give my client "full access" to their PHP application's MySQL database?

  - by Micah Delane Bolen

  I am building a PHP application for a client and I'm seriously considering WordPress or a simple framework that will allow me to quickly build out features like forums, etc. However, the client is adamant about having "full access" to the database and the ability to "mine the data." Unfortunately, I'm almost certain they will be disappointed when they realize they won't be able to easily glean meaningful insight by looking at serialized fields in wp_usermeta, etc. One thought I had was to replicate a variation on the live database where I flatten out all of those ambiguous and/or serialized fields into something that is then parsable by a mere mortal using a tool as simple as phpMyAdmin. Unfortunately, the client is not going to settle for a simple backend dashboard where I create the custom reports for them even though I know that would be the easiest and most sane approach.

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• How to distribute a unique database already in production?

  - by JVerstry

  Let's assume a successful web spring application running on a MySql or PostGre kind of database. The traffic is becoming so high and the amount of data is becoming so big that a distributed dataase solution needs to be implemented. It is a scalability issue. Let's assume this application is using Hibernate and the data access layer is cleanly separated with DAO objects. What would be the best strategy to scale this database? Does anyone have hands on experience to share? Is it possible to minimize sharding code (Shard) in the application? Ideally, one should be able to add or remove databases easily. A failback solution is welcome too. I am not looking for you could go for sharding or you could go no sql kind of answers. I am looking for deeper answers from people with experience.

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• Delete ONE SPECIFIC table of a database - leave the rest intact

  - by Jayomat

  Hi, I have a database where I store two different kinds of data. One table is for favorite routes, the other stores the retrieved routes from a server. I can retrieve the routes etc just fine. But after retrieving the first Route, pressing back or HOME, and then retrieving another route, the routes table is filled with all the old routes plus the new ones. So my question: how do I delete ONLY the routes table and not the whole database because I don't want to delete the added favorites....?! I found the following function in the android docs: public int delete (String table, String whereClause, String[] whereArgs) and I tried to implement it, but I must pass a SQLiteDataBase as an argument. But how? I implemented: public void deleteTableRoutes(SQLiteDataBase db){ db.delete("routes", null, null); } But I want to call this function from a different class where I have no reference to the database.. so what do I have to pass as an argument? Or how do I get a reference to my database? I build my database upon the code example of the NotePadExample from the dev docs. How to solve this problem? thanks

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• Database Change Auditing - Part of or Abstracted from ORM / Application Layer?

  - by BrandonV

  My fellow developers and I are at a crossroads in how to go about continuing our auditing of database changes. Most of our applications log changes via INSERT, UPDATE, and DELETE triggers. A few of our newer applications audit at the ORM layer; specifically using Hibernate Envers. While ORM layer auditing provides a much cleaner interface and is much more maintainable, it will not capture any manual database changes that are made. ORM layer auditing also means that our libraries will currently require a dependency on our ORM implementation unless, specifically in our case for example, JPA plans on providing something in the near future. Is there a common paradigm that addresses this?

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• Connecting To SQL Database In C#

  - by Soo

  Hey everyone, I'm pretty familiar with SQL syntax (via MySQL) and am just getting my feet wet with C# and SQL server. I currently have a .sdf database on my C:\ drive and want to connect to it in C#. I added the database as a data source and now need help figuring out how to get data from the database in my C# application. I just want to be able to set an object to the data in my SQL database so I can manipulate it using C#. Thanks in advance for replies.

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• SQL Source Control with Vault Support Officially Released

  - by Ajarn Mark Caldwell

  HOORAY!  It is officially here!  Today, Red-Gate officially released SQL Source Control version 2.1 with support for Vault. While we have been happily and successfully running the beta version (a.k.a. the Early Access release) of Red-Gate SQL Source Control with support for Vault for quite a while, it is good to have the official RTM (or GOLD, or PROD, or whatever you call your “no-longer-in-beta”) release of the product. As a courtesy to those who have not already read the series, allow me to provide you with these links to my previous posts about this fantastic tool. Using SQL Source Control with Fortress or Vault – Part 1 – Introduction and initial thoughts about the tool and source controlling SQL code in general. Using SQL Source Control with Fortress or Vault – Part 2 – Additional details about included features and a few warnings. Source Control and SQL Development – Part 3 – How we did it in the good ol’ days before this product came along. Using SQL Source Control and Vault Professional Part 4 – A few closing thoughts.

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• Copying contents of a MySQL table to a table in another (local) database

  - by Philip Eve

  I have two MySQL databases for my site - one is for a production environment and the other, much smaller, is for a testing/development environment. Both have identical schemas (except when I am testing something I intend to change, of course). A small number of the tables are for internationalisation purposes: TransLanguage - non-English languages TransModule - modules (bundles of phrases for translation, that can be loaded individually by PHP scripts) TransPhrase - individual phrases, in English, for potential translation TranslatedPhrase - translations of phrases that are submitted by volunteers ChosenTranslatedPhrase - screened translations of phrases. The volunteers who do translation are all working on the production site, as they are regular users. I wanted to create a stored procedure that could be used to synchronise the contents of four of these tables - TransLanguage, TransModule, TransPhrase and ChosenTranslatedPhrase - from the production database to the testing database, so as to keep the test environment up-to-date and prevent "unknown phrase" errors from being in the way while testing. My first effort was to create the following procedure in the test database: CREATE PROCEDURE `SynchroniseTranslations` () LANGUAGE SQL NOT DETERMINISTIC MODIFIES SQL DATA SQL SECURITY DEFINER BEGIN DELETE FROM `TransLanguage`; DELETE FROM `TransModule`; INSERT INTO `TransLanguage` SELECT * FROM `PRODUCTION_DB`.`TransLanguage`; INSERT INTO `TransModule` SELECT * FROM `PRODUCTION_DB`.`TransModule`; INSERT INTO `TransPhrase` SELECT * FROM `PRODUCTION_DB`.`TransPhrase`; INSERT INTO `ChosenTranslatedPhrase` SELECT * FROM `PRODUCTION_DB`.`ChosenTranslatedPhrase`; END When I try to run this, I get an error message: "SELECT command denied to user 'username'@'localhost' for table 'TransLanguage'". I also tried to create the procedure to work the other way around (that is, to exist as part of the data dictionary for the production database rather than the test database). If I do it that, way, I get an identical message except it tells me I'm denied the DELETE command rather than SELECT. I have made sure that my user has INSERT, DELETE, SELECT, UPDATE and CREATE ROUTINE privileges on both databases. However, it seems as though MySQL is reluctant to let this user exercise its privileges on both databases at the same time. How come, and is there a way around this?

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• Database recovery model change notification report for SQL Server

  The database recovery model plays a crucial role for the recovery of a database. With several DBAs having access to a SQL Server instance there are bound to be changes that are not communicated. In this tip we cover a monitoring solution we deployed at our company to alert the DBAs if a database recovery model is different than what it is expected. The Future of SQL Server MonitoringMonitor wherever, whenever with Red Gate's SQL Monitor. See it live in action now.

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• How Do I Escape Apostrophes in Field Valued in SQL Server?

  - by Mikecancook

  I asked a question a couple days ago about creating INSERTs by running a SELECT to move data to another server. That worked great until I ran into a table that has full on HTML and apostrophes in it. What's the best way to deal with this? Lucking there aren't too many rows so it is feasible as a last resort to 'copy and paste'. But, eventually I will need to do this and the table by that time will probably be way too big to copy and paste these HTML fields. This is what I have now: select 'Insert into userwidget ([Type],[UserName],[Title],[Description],[Data],[HtmlOutput],[DisplayOrder],[RealTime],[SubDisplayOrder]) VALUES (' + ISNULL('N'''+Convert(varchar(8000),Type)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),Username)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),Title)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),Description)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),Data)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),HTMLOutput)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),DisplayOrder)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),RealTime)+'''','NULL') + ',' + ISNULL('N'''+Convert(varchar(8000),SubDisplayOrder)+'''','NULL') + ')' from userwidget Which is works fine except those pesky apostrophes in the HTMLOutput field. Can I escape them by having the query double up on the apostrophes or is there a way of encoding the field result so it won't matter?

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• How can I optimize retrieving lowest edit distance from a large table in SQL?

  - by Matt

  Hey, I'm having troubles optimizing this Levenshtein Distance calculation I'm doing. I need to do the following: Get the record with the minimum distance for the source string as well as a trimmed version of the source string Pick the record with the minimum distance If the min distances are equal (original vs trimmed), choose the trimmed one with the lowest distance If there are still multiple records that fall under the above two categories, pick the one with the highest frequency Here's my working version: DECLARE @Results TABLE ( ID int, [Name] nvarchar(200), Distance int, Frequency int, Trimmed bit ) INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@Source, [Name])) As Distance, Frequency, 'False' As Trimmed FROM MyTable INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@SourceTrimmed, [Name])) As Distance, Frequency, 'True' As Trimmed FROM MyTable SET @ResultID = (SELECT TOP 1 ID FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @Result = (SELECT TOP 1 [Name] FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultDist = (SELECT TOP 1 Distance FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultTrimmed = (SELECT TOP 1 Trimmed FROM @Results ORDER BY Distance, Trimmed, Frequency) I believe what I need to do here is to.. Not dumb the results to a temporary table Do only 1 select from `MyTable` Setting the results right in the select from the initial select statement. (Since select will set variables and you can set multiple variables in one select statement) I know there has to be a good implementation to this but I can't figure it out... this is as far as I got: SELECT top 1 @ResultID = ID, @Result = [Name], (dbo.Levenshtein(@Source, [Name])) As distOrig, (dbo.Levenshtein(@SourceTrimmed, [Name])) As distTrimmed, Frequency FROM MyTable WHERE /* ... yeah I'm lost */ ORDER BY distOrig, distTrimmed, Frequency Any ideas?

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