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• Should I use a huge composite primary key or just a unique id?

  - by Jack

  I have been trying to do web scraping of a particular site and storing the results in a database. My original assumptions about the data allowed a schema where I could use fairly reasonable composite primary keys (usually containing only 2 or 3 fields) but as time went on, I realized that my original assumptions about the data were wrong and my primary keys were not as unique as I thought they were, so I have slowly been expanding them to contain more and more fields. In fact, I have recently come to believe that their database has no constraints whatsoever. Just today, I have finally expanded my a primary key for one of my tables to contain every field in that table and I thought now would be a good time to ask: is it better to add an auto-incrementing column that is just a unique id or just leave a composite primary key on the entire table?

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• Inexpensive (used) hardware for Xen virtualization test?

  - by Jason Antman

  Virtualization is one of the areas where I could really use some experience. I also run quite a few services (web, mail, dns, etc.) out of my home. Since most of my hardware is getting a bit old (I'm running on stuff that was surplused years ago...) I decided that it's about time I start renewing some things, and also play around with virtualization a bit more. My plan is to setup a SAN box (simple iSCSI target, relatively inexpensive gigE switch), get a pair (for starters) of new servers, and start building some new stuff with Xen, specifically planning on playing with live migration and full virtualization. Does anyone have recommendations for used, older "servers" (really anything in a rack-mount form factor, I'm not too worried about things like iLO/iLOM for the test nodes) that support VT-x/AMD-V? I'm biased to HP, but it looks like they didn't make Proliants with VT-x/Vanderpool processors until G6 (for the DL360) or so, which is way out of my price range. I'm looking in the sub-$300 range (or less, if possible), used, probably Ebay. Any recommendations are greatly appreciated. Edit:And, to catch this before the comments start coming - these are personal systems. I have first-generation Proliants still in use (I got them as corporate surplus in 05, they've been running since then, and probably were running since 01 or 02 prior to being sold). I don't need anything shiny and new - I've got a bunch of old boxes, at least one complete replacement for every model in use, and that's fine for me (and easy on the wallet).

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• How to: Avoid Inserting Related Entities?

  - by niaher

  I have this schema: I want to insert an Order with OrderItems into database, so I wrote this method: public void SaveOrder(Order order) { using (var repository = new StoreEntities()) { // Add order. repository.Orders.AddObject(order); // Add order items. foreach (OrderItem orderItem in order.OrderItems) { repository.OrderItems.AddObject(orderItem); } repository.SaveChanges(); } } Everything is inserted just fine, except that new Product records are inserted too, which is not what I want. What I want is to insert Order and its OrderItems, without going any further down the object graph. How can that be achieved? Any help is really appreciated, thank you.

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• References/walkthroughs for maintaining database schemas with Visual Studio 2010?

  - by user206356

  I have Visual Studio 2010 Beta 2 and SQL Server 2008 installed. I'm working with a populated database and want to modify various column types. SQL Server Management Studio requires me to drop tables to do this, and get pretty finicky given my moderate level of knowledge of SQL Server. However, I heard the new database project type supports changing the database schema to the desired format and it will handle creating and running all the scripts to implement the changes. I've created a VS2010 database project using the existing database as the source, but so far haven't had much luck figuring out the appropriate method to make the changes without getting an error. As a result, I'm looking for any reference info I can find on using VS2010's capabilities in this area. Any suggestions?

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• significance of index name in creating an index (mySQL)

  - by Will

  I've done something like this in order to use on duplicate key update: CREATE UNIQUE INDEX blah on mytable(my_col_to_make_an_index); and its worked just fine. I'm just not sure what the purpose of the index name is -- in this case 'blah'. The stuff I've read says to use one but I can't fathom why. It doesn't seem to be used in queries, although I can see it if I export the schema. So ... what purpose does the index name serve? If it helps the line in the CREATE TABLE ends up looking like: UNIQUE KEY `clothID` (`clothID`)

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• Can XSD elements have more than one <annotation>?

  - by Scott

  I have a common data schema in XSD that is used by two different applications, A and B, each uses the data differently. I want to document the different business rules per application. Can I do this? <xs:complexType name="Account"> <xs:annotation app="A"> <xs:documentation> The Account entity must be used this way for app A </xs:documentation> </xs:annotation> <xs:annotation app="B"> <xs:documentation> The Account entity must be used this way for app B </xs:documentation> </xs:annotation> <xs:complexContent> ...

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• Embedded analog of CouchDB, same as sqlite for SQL Server

  - by Mike Chaliy

  I like an idea of document oriented databases like CouchDB. I am looking for simple analog. My requirements is just: persistance storage for schema less data; some simple in-proc quering; good to have transactions and versioning; ruby API; map/reduce is aslo good to have; should work on shared hosting What I do not need is REST/HTTP interfaces (I will use it in-proc). Also I do not need all scalability stuff.

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• Easy way to compute how close an auto_increment is to its maximum value?

  - by David M

  So yesterday we had a table that has an auto_increment PK for a smallint that reached its maximum. We had to alter the table on an emergency basis, which is definitely not how we like to roll. Is there an easy way to report on how close each auto_increment field that we use is to its maximum? The best way I can think of is to do a SHOW CREATE TABLE statement, parse out the size of the auto-incremented column, then compare that to the AUTO_INCREMENT value for the table. On the other hand, given that the schema doesn't change very often, should I store information about the columns' maximum values and get the current AUTO_INCREMENT with SHOW TABLE STATUS?

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• Programming to interfaces while mapping with Fluent NHibernate.

  - by Lucious

  Fluent Mapping I Have the following scenario public class CustomerMap : ClassMap { public CustomerMap() { Table("Customer"); Id(c = c.Id); Map(c = c.Name); HasMany(c = c.Orders); } } public class OrderMap : ClassMap<IOrder> { public OrderMap() { Table("Orders"); References(o => o.Customer).Access.; Id(o => o.Id); Map(o => o.DateCreated); } } Problems When schema exported the order table has two columns ICustomer_Id,Customer_Id. refers to an unmapped class Order exception Can you please help me out?

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• How to coerce type of ActiveRecord attribute returned by :select phrase on joined table?

  - by tribalvibes

  Having trouble with AR 2.3.5, e.g.: users = User.all( :select => "u.id, c.user_id", :from => "users u, connections c", :conditions => ... ) Returns, e.g.: => [#<User id: 1000>] >> users.first.attributes => {"id"=>1000, "user_id"=>"1000"} Note that AR returns the id of the model searched as numeric but the selected user_id of the joined model as a String, although both are int(11) in the database schema. How could I better form this type of query to select columns of tables backing multiple models and retrieving their natural type rather than String ? Seems like AR is punting on this somewhere. How could I coerce the returned types at AR load time and not have to tack .to_i (etc.) onto every post-hoc access?

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• Hibernate won't autogenerate sequence table

  - by Jason

  I'm trying to use a sequence table to generate keys for my entities. I notice that if I just use the @GeneratedValue(strategy=GenerationType.TABLE) with no explicit generator, Hibernate will automatically create the hibernate_sequences table in my DB if it doesn't exist. This is great. However, I wanted to make some changes to the sequence table, so I created a @TableGenerator like the following: @GeneratedValue(strategy=GenerationType.TABLE, generator="vdat_seq") @TableGenerator(name="vdat_seq", table="VDAT_SEQ", pkColumnName="seq_name", valueColumnName="seq_next_val", allocationSize=1) This works fine if I manually create the VDAT_SEQ table in my schema; Hibernate won't auto-create it anymore. This causes an issue in my unit tests, since I'd rather not have to manually create a table and maintain it on our testing DB. Is there a configuration variable or some other way to get Hibernate to generate the sequence table?

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• How can I create a sample SQLLite DB for my iPhone app?

  - by Dr Dork

  I'm diving in to iPhone development and I'm building an iPhone app that uses the Core Data framework and my first task will be to get the model setup with a few that will display it. Thus far, I have the model defined and my Managed Object Files created, but I don't have a database with any sample data. What's a quick way to create a DB that conforms to my schema? Are there any tools that can generate a sample DB using my schemas? Is there a good tool I can use to directly manipulate the data in DB for testing purposes? Thanks in advance for your help! I'm going to continue researching this question right now.

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• validate XML with XSD in c++

  - by katl

  Hi! Im pretty new to both XML validation and C++ (more familiar with Java..) so I guess this is a trivial question. If I have a XML file and a XSD schema, how is the best way to validate them? Id like to to this in c++ without using external libraries, or as little libraries as possible, is it possible? Other ideas of how this can be done? I want a simple solution, the output needed is just if the validation i successful or not. Any help is appreciated // Katarina

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• Authenticating model - best practices

  - by zerkms

  I come into ASP.NET from php so the reason why i ask my question is because it's totally different nature of how application works and handles requests. well, i have an exists table with user creditians, such as: id, login, password (sha hashed), email, phone, room i have built custom membership provider so it can handle my own database authentication schema. and now i'm confused, because User.Identity.Name contains only user's login, but not the complete object (i'm using linq2sql to communicate with database and i need in it's User object to work). at php applications i just store user object at some static method at Auth class (or some another), but here at ASP.NET MVC i cannot do this, because static member is shared across all requests and permanent, and not lives within only current request (as it was at php). so my question is: how and where should i retrieve and store linq2sql user object to work with it within current and only current request? (after request processed successfully i expect it will be disposed from memory and on next request will be created again). or i'm following totally wrong way?

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• MySQL Insert Query Randomly Takes a Long Time

  - by ShimmerTroll

  I am using MySQL to manage session data for my PHP application. When testing the app, it is usually very quick and responsive. However, seemingly randomly the response will stall before finally completing after a few seconds. I have narrowed the problem down to the session write query which looks something like this: INSERT INTO Session VALUES('lvg0p9peb1vd55tue9nvh460a7', '1275704013', '') ON DUPLICATE KEY UPDATE sessAccess='1275704013',sessData=''; The slow query log has this information: Query_time: 0.524446 Lock_time: 0.000046 Rows_sent: 0 Rows_examined: 0 This happens about 1 out of every 10 times. The query usually only takes ~0.0044 sec. The table is InnoDB with about 60 rows. sessId is the primary key with a BTREE index. Since this is accessed on every page view, it is clearly not an acceptable execution time. Why is this happening? Update: Table schema is: sessId:varchar(32), sessAccess:int(10), sessData:text

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• Improve SQL query performance

  - by Anax

  I have three tables where I store actual person data (person), teams (team) and entries (athlete). The schema of the three tables is: In each team there might be two or more athletes. I'm trying to create a query to produce the most frequent pairs, meaning people who play in teams of two. I came up with the following query: SELECT p1.surname, p1.name, p2.surname, p2.name, COUNT(*) AS freq FROM person p1, athlete a1, person p2, athlete a2 WHERE p1.id = a1.person_id AND p2.id = a2.person_id AND a1.team_id = a2.team_id AND a1.team_id IN ( SELECT id FROM team, athlete WHERE team.id = athlete.team_id GROUP BY team.id HAVING COUNT(*) = 2 ) GROUP BY p1.id ORDER BY freq DESC Obviously this is a resource consuming query. Is there a way to improve it?

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• Need help in understanding a SELECT query

  - by Grant Smith

  I have a following query. It uses only one table (Customers) from Northwind database. I completely have no idea how does it work, and what its intention is. I hope there is a lot of DBAs here so I ask for explanation. particularly don't know what the OVER and PARTITION does here. WITH NumberedWomen AS ( SELECT CustomerId ,ROW_NUMBER() OVER ( PARTITION BY c.Country ORDER BY LEN(c.CompanyName) ASC ) women FROM Customers c ) SELECT * FROM NumberedWomen WHERE women > 3 If you needed the db schema, it is here

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• Help on choosing which SQL Server 2008 scale-out solution to pick (replication, ...)

  - by usr

  I am currently crossing the jungle of SQL Server scale-out technologies like replication, log-shipping, mirroring... I have the following constraints on my choice: I want the read-only load to be spread accross the primary and the secondary (mirror, subscriber) server Write load can be sent directly to the primary server The solution should be nearly maintainance free. Schema changes should just replicate to the secondary server (attention: replication has some serious constraints here as it seems) Written data should be accessible very quickly (in under 1s, but better would be instantaneously) on the secondary server On server failure I can tollerate up to one hour of data loss easily. I am more concerned with easy scalability Here are some options for what I could pick: http://msdn.microsoft.com/en-us/library/bb510414.aspx. Any experience you could share?

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• Why do I have to set the max length of every damn text column in the database?

  - by John Leidegren

  Why is it that every RDBMS insists that you tell it what the max length of a text field is going to be... why can't it just infer this information form the data that's put into the database? I've mostly worked with MS SQL Server, but every other database I know also demands that you set these arbitrary limits on your data schema. The reality is that this is not particulay helpful or friendly to work with becuase the business requirements change all the time and almost every day some end-user is trying to put a lot of text into that column. Does any one with some inner working knowledge of a RDBMS know why we just don't infer the limits from the data that's put into the storage? I'm not talking about guessing the type information, but guessing the limits of a particular text column. I mean, there's a reason why I don't use nvarchar(max) on every text column in the database.

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• Process for Upgrading from RedBean 3.5 to RedBean 4

  - by Jay Haase

  I am currently using RedBean version 3.5. I think I would like to move to the latest version of RedBean, version 4. I have found no documentation about upgrade process and have a number of significant questions: Is my RedBean 3.5 database schema compatible 4, or will up have to migrate all of the tables to some new format? Is any of my RedBean 3.5 code compatible with version 4, or wouldI need to rewrite all of my code that uses RedBean 3.5? Would it make more sense to upgrade to Doctrine? As a side note, I am also feeling concerned about RedBean's drop of support for Composer, which I have found to be über helpful in managing the various versions of libraries I am using.

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• Solr alphabetical sorting trouble. Sorting uppercase then lowercase for string type field

  - by Alauddin Ansari

  I've crated a title field with list below: Asking is good But answering is best join the group like this You are the best hey dudes. whass up When I'm sorting this ASC (&sort=title ASC) Asking is good But answering is best You are the best hey dudes. whass up join the group like this and (&sort=title DESC) join the group like this hey dudes. whass up You are the best But answering is best Asking is good But I'm expecting result like: (&sort=title ASC) Asking is good But answering is best hey dudes. whass up join the group like this You are the best schema.xml <field name="title" type="text_general" indexed="true" stored="true"/> <field name="title_sort" type="string" indexed="true" stored="false"/> <copyField source="title" dest="title_sort" /> I'm using title_sort field to sort (also tried title field) Please tell me where I'm going wrong

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• Generate service layer with Hibernate

  - by gmate

  Hi all! I generate *.hbm.xml mapping files and *.java file from the DB schema, with Hibernate tools. My question is, that is there any option, to generate service classes also? These are the classes where I implement the store(), find(), delete(), etc... methods. I know that for C# there are many solutions to generate almost everything. I'm looking for the same, but with Hibernate. Is there any? Thanks for every reply in advance!

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• Desgining a database with flexible user profile

  - by Mughrabi

  Hi, Am working on a design where I can have flexible attributes for a user & am confused how to continue the design of the schema. I made a table where I kept system needed information called users id username password Now, I wish to create a profile table and have one to one relation where all the other attributes in profile table such as email, first name, last name..etc. My question is, is there a way to add a third table in which even profile will be flexible if my clients need to create a new attribute he/she won't need any customization to the code? Regards,

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• Optimal search queries

  - by Macros

  Following on from my last question http://stackoverflow.com/questions/2788082/sql-server-query-performance, and discovering that my method of allowing optional parameters in a search query is sub optimal, does anyone have guidelines on how to approach this? For example, say I have an application table, a customer table and a contact details table, and I want to create an SP which allows searching on some, none or all of surname, homephone, mobile and app ID, I may use something like the following: select * from application a inner join customer c on a.customerid = a.id left join contact hp on (c.id = hp.customerid and hp.contacttype = 'homephone') left join contact mob on (c.id = mob.customerid and mob.contacttype = 'mobile') where (a.ID = @ID or @ID is null) and (c.Surname = @Surname or @Surname is null) and (HP.phonenumber = @Homphone or @Homephone is null) and (MOB.phonenumber = @Mobile or @Mobile is null) The schema used above isn't real, and I wouldn't be using select * in a real world scenario, it is the construction of the where clause I am interested in. Is there a better approach, either dynamic sql or an alternative which can achieve the same result, without the need for many nested conditionals. Some SPs may have 10 - 15 criteria used in this way

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• What is the best way to partition large tables in SQL Server?

  - by RyanFetz

  In a recent project the "lead" developer designed a database schema where "larger" tables would be split across two seperate databases with a view on the main database which unioned the two seperate database-tables together. The main database is what the application was driven off of so these tables looked and felt like ordinary tables (except some quirkly things around updating). This seemed like a HUGE performance problem. We do see problems with performance around these tables but nothing to make him change his mind about his design. Just wondering what is the best way to do this, or if it is even worth doing?

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