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  • about null values!

    - by user329820
    Hi I have a question that if we declare a variable and then do not set it explicitly to null value then it would be null outomatically ,i mean that the below code will return true or false ? thanks DECLARE @val CHAR(4) If @val = NULL

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  • Can I do transactions and locks in CouchDB?

    - by damian
    I need to do transactions (begin, commit or rollback), locks (select for update). How can I do it in a document model db? Edit: The case is this: I want to run an auctions site. And I think how to direct purchase as well. In a direct purchase I have to decrement the quantity field in the item record, but only if the quantity is greater than zero. That is why I need locks and transactions. I don't know how to address that without locks and/or transactions. Can I solve this with CouchDB?

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  • How can I view live MySQL queries?

    - by barfoon
    Hey all, I am just wondering if its possible to trace MySQL queries on my linux server as they happen? For example I'd love to set up some sort of listener, then request a web page and view all of the queries the engine executed, or just view all of the queries being run on a production server. Are there tools to do this? Thank you,

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  • Getting wierd issue with TO_NUMBER function in Oracle

    - by Fazal
    I have been getting an intermittent issue when executing to_number function in the where clause on a varchar2 column if number of records exceed a certain number n. I used n as there is no exact number of records on which it happens. On one DB it happens after n was 1 million on another when it was 0.1. million. E.g. I have a table with 10 million records say Table Country which has field1 varchar2 containing numberic data and Id If I do a query as an example select * from country where to_number(field1) = 23 and id 1 and id < 100000 This works But if i do the query select * from country where to_number(field1) = 23 and id 1 and id < 100001 It fails saying invalid number Next I try the query select * from country where to_number(field1) = 23 and id 2 and id < 100001 It works again As I only got invalid number it was confusing, but in the log file it said Memory Notification: Library Cache Object loaded into SGA Heap size 3823K exceeds notification threshold (2048K) KGL object name :with sqlplan as ( select c006 object_owner, c007 object_type,c008 object_name from htmldb_collections where COLLECTION_NAME='HTMLDB_QUERY_PLAN' and c007 in ('TABLE','INDEX','MATERIALIZED VIEW','INDEX (UNIQUE)')), ws_schemas as( select schema from wwv_flow_company_schemas where security_group_id = :flow_security_group_id), t as( select s.object_owner table_owner,s.object_name table_name, d.OBJECT_ID from sqlplan s,sys.dba_objects d It seems its related to SGA size, but google did not give me much help on this. Does anyone have any idea about this issue with TO_NUMBER or oracle functions for large data?

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  • Fact table with multiple facts

    - by Jeff Meatball Yang
    I have a dimension (SiteItem) has two important facts: perUserClicks perBrowserClicks however, within this dimension, I have groups of dimensions based on an attribute column (let's call the groups AboveFoldItems, LeftNavItems, OnTheFlyItems, etc.) each have more facts that are specific to that group: AboveFoldItems: eyeTime, loadTime LeftNavItems: mouseOverTime OnTheFlyItems: doesn't have any extra, but may in the future Is the following fact table schema ok? DateKey SessionKey SiteItemKey perUserClicks perBrowserClicks eyeTime loadTime mouseOverTime It seems a little wasteful since only some columns pertain to some dimension keys (the irrelevant facts are left NULL). But... this seems like it would be a common problem, so there should be a common solution for this, right?

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  • Can somebody suggest good learning source of IMS?

    - by Raja Reddy
    I would like to learn working with IMS, can somebody suggest me a good source? I'm not sure if it matters to say that I have quite good exposure and experience with INSYNC DB2 and QMF. So anything that can depict and explain the advantages and disadvantages over IMS would be really helpful. Thanks for your help beforehand..

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  • WPF: How to bind and update display with DataContext

    - by Am
    I'm trying to do the following thing: I have a TabControl with several tabs. Each TabControlItem.Content points to PersonDetails which is a UserControl Each BookDetails has a dependency property called IsEditMode I want a control outside of the TabControl , named ToggleEditButton, to be updated whenever the selected tab changes. I thought I could do this by changing the ToggleEditButton data context, by it doesn't seem to work (but I'm new to WPF so I might way off) The code changing the data context: private void tabControl1_SelectionChanged(object sender, SelectionChangedEventArgs e) { if (e.Source is TabControl) { if (e.Source.Equals(tabControl1)) { if (tabControl1.SelectedItem is CloseableTabItem) { var tabItem = tabControl1.SelectedItem as CloseableTabItem; RibbonBook.DataContext = tabItem.Content as BookDetails; ribbonBar.SelectedTabItem = RibbonBook; } } } } The DependencyProperty under BookDetails: public static readonly DependencyProperty IsEditModeProperty = DependencyProperty.Register("IsEditMode", typeof (bool), typeof (BookDetails), new PropertyMetadata(true)); public bool IsEditMode { get { return (bool)GetValue(IsEditModeProperty); } set { SetValue(IsEditModeProperty, value); SetValue(IsViewModeProperty, !value); } } And the relevant XAML: <odc:RibbonTabItem Title="Book" Name="RibbonBook"> <odc:RibbonGroup Title="Details" Image="img/books2.png" IsDialogLauncherVisible="False"> <odc:RibbonToggleButton Content="Edit" Name="ToggleEditButton" odc:RibbonBar.MinSize="Medium" SmallImage="img/edit_16x16.png" LargeImage="img/edit_32x32.png" Click="Book_EditDetails" IsChecked="{Binding Path=IsEditMode, Mode=TwoWay}"/> ... There are two things I want to accomplish, Having the button reflect the IsEditMode for the visible tab, and have the button change the property value with no code behind (if posible) Any help would be greatly appriciated.

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  • Grails multi column indexes

    - by Kimble
    Can someone explain how to define multi column indexes in Grails? The documentation is at best sparse. This for example does not seem to work at all: http://grails.org/GORM+Index+definitions I've had some luck with this, but the results seems random at best. Definitions that works in one domain class does not when applied to another (with different names of course). http://www.grails.org/doc/1.1/guide/single.html#5.5.2.6%20Database%20Indices Some working examples and explanations would be highly appreciated!

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  • Sql server query using function and view is slower

    - by Lieven Cardoen
    I have a table with a xml column named Data: CREATE TABLE [dbo].[Users]( [UserId] [int] IDENTITY(1,1) NOT NULL, [FirstName] [nvarchar](max) NOT NULL, [LastName] [nvarchar](max) NOT NULL, [Email] [nvarchar](250) NOT NULL, [Password] [nvarchar](max) NULL, [UserName] [nvarchar](250) NOT NULL, [LanguageId] [int] NOT NULL, [Data] [xml] NULL, [IsDeleted] [bit] NOT NULL,... In the Data column there's this xml <data> <RRN>...</RRN> <DateOfBirth>...</DateOfBirth> <Gender>...</Gender> </data> Now, executing this query: SELECT UserId FROM Users WHERE data.value('(/data/RRN)[1]', 'nvarchar(max)') = @RRN after clearing the cache takes (if I execute it a couple of times after each other) 910, 739, 630, 635, ... ms. Now, a db specialist told me that adding a function, a view and changing the query would make it much more faster to search a user with a given RRN. But, instead, these are the results when I execute with the changes from the db specialist: 2584, 2342, 2322, 2383, ... This is the added function: CREATE FUNCTION dbo.fn_Users_RRN(@data xml) RETURNS varchar(100) WITH SCHEMABINDING AS BEGIN RETURN @data.value('(/data/RRN)[1]', 'varchar(max)'); END; The added view: CREATE VIEW vwi_Users WITH SCHEMABINDING AS SELECT UserId, dbo.fn_Users_RRN(Data) AS RRN from dbo.Users Indexes: CREATE UNIQUE CLUSTERED INDEX cx_vwi_Users ON vwi_Users(UserId) CREATE NONCLUSTERED INDEX cx_vwi_Users__RRN ON vwi_Users(RRN) And then the changed query: SELECT UserId FROM Users WHERE dbo.fn_Users_RRN(Data) = '59021626919-61861855-S_FA1E11' Why is the solution with a function and a view going slower?

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  • How Can i Create This Complicated Query ?

    - by mTuran
    Hi, I have 3 tables: projects, skills and project_skills. In projects table i hold project's general data. Second table skills i hold skill id and skill name also i have projects_skills table which is hold project's skill relationships. Here is scheme of tables: CREATE TABLE IF NOT EXISTS `project_skills` ( `project_id` int(11) NOT NULL, `skill_id` int(11) NOT NULL, KEY `project_id` (`project_id`), KEY `skill_id` (`skill_id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_turkish_ci; CREATE TABLE IF NOT EXISTS `projects` ( `id` int(11) NOT NULL AUTO_INCREMENT, `employer_id` int(11) NOT NULL, `project_title` varchar(100) COLLATE utf8_turkish_ci NOT NULL, `project_description` text COLLATE utf8_turkish_ci NOT NULL, `project_budget` int(11) NOT NULL, `project_allowedtime` int(11) NOT NULL, `project_deadline` datetime NOT NULL, `total_bids` int(11) NOT NULL, `average_bid` int(11) NOT NULL, `created` datetime NOT NULL, `active` tinyint(1) NOT NULL, PRIMARY KEY (`id`), KEY `created` (`created`), KEY `employer_id` (`employer_id`), KEY `active` (`active`), FULLTEXT KEY `project_title` (`project_title`,`project_description`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_turkish_ci AUTO_INCREMENT=3 ; CREATE TABLE IF NOT EXISTS `skills` ( `id` int(11) NOT NULL AUTO_INCREMENT, `category` int(11) NOT NULL, `name` varchar(100) COLLATE utf8_turkish_ci NOT NULL, `seo_name` varchar(100) COLLATE utf8_turkish_ci NOT NULL, `total_projects` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `seo_name` (`seo_name`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_turkish_ci AUTO_INCREMENT=224 ; I want to select projects with related skill names. I think i have to use JOIN but i don't know how can i do. Thanks

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  • How to model a mutually exclusive relationship in sql server

    - by littlechris
    Hi, I have to add functionality to an existing application and I've run into a data situation that I'm not sure how to model. I am being restricted to the creation of new tables and code. If I need to alter the existing structure I think my client may reject the proposal..although if its the only way to get it right this is what I will have to do. I have an Item table that can me link to any number of tables, and these tables may increase over time. The Item can only me linked to one other table, but the record in the other table may have many items linked to it. Examples of the tables/entities being linked to are "Person", "Vehicle", "Building", "Office". These are all separate tables. Example of Items are "Pen", "Stapler", "Cushion", "Tyre", "A4 Paper", "Plastic Bag", "Poster", "Decoration" For instance a "Poster" may be allocated to a "Person" or "Office" or "Building". In the future if they add a "Conference Room" table it may also be added to that. My intital thoughts are: Item { ID, Name } LinkedItem { ItemID, LinkedToTableName, LinkedToID } The LinkedToTableName field will then allow me to identify the correct table to link to in my code. I'm not overly happy with this solution, but I can't quite think of anything else. Please help! :) Thanks!

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  • Ruby on Rails Mongrel web server stuck when MySQL service is running

    - by Marcos Buarque
    Hi, I am a Ruby on Rails newbie and already have a problem. I have started the Mongrel web server and it works fine when MySQL service isn't running. But when MySQL is on, Mongrel stucks. It ceases from serving the pages. So far, I have tested the localhost:3000 URL. When MySQL is off, it serves the page. When I click "about application's environment", I get the messasge (of course) "Can't connect to MySQL server on 'localhost' (10061)". After starting the MySQL service and refreshing, I get no more answer and Mongrel does not serve the webpage. It gets stuck with no answer to the browser. Then I have to stop the webserver and restart it. I have installed mysql2 gem with the command gem install mysql2. I was able to create the _test and _development databases with the command line rake db:create. I have tested with MySQL root user and blank password and also tried with a superuser user I have created. No success. Here is the server log: ======================== Started GET "/rails/info/properties" for 127.0.0.1 at Fri Dec 24 17:41:25 -0200 2010 Mysql2::Error (Can't connect to MySQL server on 'localhost' (10061)): Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms) Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (5.0ms) Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (35.0ms) ================= I am running on a Windows 7 environment with firewall down.

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  • Static DB Provider in ASP.NET MVC Causing Memory Leak

    - by user364685
    Hi, I have got an app I'm going to write in ASP.NET MVC and I want to create a DatabaseFactory object something like this:- public class DatabaseFactory { private string dbConn get { return <gets from config file>; } public IDatabaseTableObject GetDatabaseTable() { IDatabaseTableObject databaseTableObject = new SQLDatabaseObject(dbConn); return databaseTableObject; } } and this works fine, but I obviously have to instantiate the DatabaseFactory in every controller that needs it. If I made this static, so I could, in theory just call DatabaseFactory.GetDatabaseTable() it would cause a memory leak, wouldn't it?

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  • Best practices for handling unique constraint violation

    - by umesh awasthi
    Hi All, While working in my application i came across a situation in which there are likely chances to Unque Constraints Violation.I have following options Catch the exception and throw it back to UI At UI check for the exception and show approrpriate Error Message This is something different idea is to Check in advance about the existance of the given Unique value before starting the whole operation. My Question is what might be the best practice to handle such situation.Currently we are using combo of Struts2+Spring 3.x+Hibernate 3.x Thanks in advance

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  • DB design abbreviations

    - by CChriss
    I know PK means primary key and FK means foreign key, but what do "rK" (in section 3) and "PF" (in sections 3, 4, 6, 7, and 8) mean on this page? http://www.databaseanswers.org/tutorial4_data_modelling/index.htm And what does "FF" mean (in the Customer_Addresses table) on this page? -I'm new so it would only let me put in one hyperlink, so copy/paste this to go to the page I'm asking about: databaseanswers.org/tutorial4_db_schema/tutorial_slide_7.htm Thanks. Edit: also, I understand the concepts of primary keys and foreign keys, but what are these other ones used for?

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  • Performance of VIEW vs. SQL statement

    - by Matt W.
    I have a query that goes something like the following: select <field list> from <table list> where <join conditions> and <condition list> and PrimaryKey in (select PrimaryKey from <table list> where <join list> and <condition list>) and PrimaryKey not in (select PrimaryKey from <table list> where <join list> and <condition list>) The sub-select queries both have multiple sub-select queries of their own that I'm not showing so as not to clutter the statement. One of the developers on my team thinks a view would be better. I disagree in that the SQL statement uses variables passed in by the program (based on the user's login Id). Are there any hard and fast rules on when a view should be used vs. using a SQL statement? What kind of performance gain issues are there in running SQL statements on their own against regular tables vs. against views. (Note that all the joins / where conditions are against indexed columns, so that shouldn't be an issue.) EDIT for clarification... Here's the query I'm working with: select obj_id from object where obj_id in( (select distinct(sec_id) from security where sec_type_id = 494 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) and sec_obj_id in ( select obj_id from object where obj_ot_id in (select of_ot_id from obj_form left outer join obj_type on ot_id = of_ot_id where ot_app_id = 87 and of_id in (select sec_obj_id from security where sec_type_id = 493 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) ) and of_usage_type_id = 131 ) ) ) ) or (obj_ot_id in (select of_ot_id from obj_form left outer join obj_type on ot_id = of_ot_id where ot_app_id = 87 and of_id in (select sec_obj_id from security where sec_type_id = 493 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) ) and of_usage_type_id = 131 ) and obj_id not in (select sec_obj_id from security where sec_type_id = 494) )

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  • Maximum Row in DBMS

    - by Am1rr3zA
    Is there any limit to maximum row of table in DBMS (specially MySQL)? I want create table for saving logfile and it's row increase so fast I want know what shoud I do to prevent any problem.

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  • In this example, would Customer or AccountInfo properly be the entity group parent?

    - by Badhu Seral
    In this example, the Google App Engine documentation makes the Customer the entity group parent of the AccountInfo entity. Wouldn't AccountInfo encapsulate Customer rather than the other way around? Normally I would think of an AccountInfo class as including all of the information about the Customer. import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.appengine.api.datastore.Key; import com.google.appengine.api.datastore.KeyFactory; @PersistenceCapable public class AccountInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; public void setKey(Key key) { this.key = key; } } // ... KeyFactory.Builder keyBuilder = new KeyFactory.Builder(Customer.class.getSimpleName(), "custid985135"); keyBuilder.addChild(AccountInfo.class.getSimpleName(), "acctidX142516"); Key key = keyBuilder.getKey(); AccountInfo acct = new AccountInfo(); acct.setKey(key); pm.makePersistent(acct);

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