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• Optimizing ROW_NUMBER() in SQL Server

  - by BlueRaja

  We have a number of machines which record data into a database at sporadic intervals. For each record, I'd like to obtain the time period between this recording and the previous recording. I can do this using ROW_NUMBER as follows: WITH TempTable AS ( SELECT *, ROW_NUMBER() OVER (PARTITION BY Machine_ID ORDER BY Date_Time) AS Ordering FROM dbo.DataTable ) SELECT [Current].*, Previous.Date_Time AS PreviousDateTime FROM TempTable AS [Current] INNER JOIN TempTable AS Previous ON [Current].Machine_ID = Previous.Machine_ID AND Previous.Ordering = [Current].Ordering + 1 The problem is, it goes really slow (several minutes on a table with about 10k entries) - I tried creating separate indicies on Machine_ID and Date_Time, and a single joined-index, but nothing helps. Is there anyway to rewrite this query to go faster?

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• Hibernate can't load Custom SQL collection

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database. add 2010/05/23 Pascal's answer is right,but the "false" value must be replaced with other expression,like "1=2".Because the "false" value would be considered to be a column of the table. select i.code from Item i where ( case length(code) when 4 then i.code=SUBSTRING(code,1,2) else 1=2 end) And I have another question about the children "bag" mapping.There isn't formula configuration option for "bag",but we can use "loader" to load a sql-query.I configure the "bag" as following.But it get a list whose size is 0.What's wrong with it? <class> ... ... <bag name="children"> <key /> <one-to-many class="Item"></one-to-many> <loader query-ref="getChildren"></loader> </bag> </class> <sql-query name="getChildren"> <load-collection alias="r" role="Item.children" /> <![CDATA[(select {r.*} from Item r join Item o where o.code=:code and ( case length(o.code) when 2 then (length(r.code)=4 and SUBSTRING(r.code,1,2)=o.code) else 1=2 end ))]]> </sql-query>

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• How to capture SQL with parameters substituted in? (.NET, SqlCommand)

  - by Bryan

  Hello, If there an easy way to get a completed SQL statement back after parameter substitution? I.e., I want to keep a logfile of all the SQL this program runs. Or if I want to do this, will I just want to get rid of Parameters, and do the whole query the old school way, in one big string? Simple Example: I want to capture the output: SELECT subcatId FROM EnrollmentSubCategory WHERE catid = 1 .. from this code: Dim subCatSQL As String = "SELECT subcatId FROM EnrollmentSubCategory WHERE catid = @catId" Dim connectionString As String = "X" Dim conn As New SqlConnection(connectionString) If conn.State = ConnectionState.Closed Then conn.Open() End If Dim cmd As New SqlCommand(subCatSQL, conn) With cmd .Parameters.Add(New SqlParameter("@catId", SqlDbType.Int, 1)) End With Console.WriteLine("Before: " + cmd.CommandText) cmd.Prepare() Console.WriteLine("After: " + cmd.CommandText) I had assumed Prepare() would do the substitutions, but apparently not. Thoughts? Advice? Thanks in advance.

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• How to get scripted programs governing game entities run in parallel with a game loop?

  - by Jim

  I recently discovered Crobot which is (briefly) a game where each player codes a virtual robot in a pseudo-C language. Each robot is then put in an arena where it fights against other robots. A robots' source code has this shape : /* Beginning file robot.r */ main() { while (1) { /* Do whatever you want */ ... move(); ... fire(); } } /* End file robot.r */ You can see that : The code is totally independent from any library/include Some predefined functions are available (move, fire, etc…) The program has its own game loop, and consequently is not called every frame My question is: How to achieve a similar result using scripted languages in collaboration with a C/C++ main program ? I found a possible approach using Python, multi-threading and shared memory, although I am not sure yet that it is possible this way. TCP/IP seems a bit too complicated for this kind of application.

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• Problem with deleting table rows using ctrl+a for row selection

  - by Frank Nimphius

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The following code is commonly shown and documented for how to access the row key of selected table rows in an ADF Faces table configured for multi row selection. public void onRemoveSelectedTableRows(ActionEvent actionEvent) {    RichTable richTable = … get access to your table instance …    CollectionModel cm =(CollectionModel)richTable.getValue();    RowKeySet rowKeySet = (RowKeySet)richTable.getSelectedRowKeys();             for (Object key : rowKeySet) {       richTable.setRowKey(key);       JUCtrlHierNodeBinding rowData = (JUCtrlHierNodeBinding)cm.getRowData();       // do something with rowData e.g.update, print, copy   }    //optional, if you changed data, refresh the table         AdfFacesContext adfFacesContext = AdfFacesContext.getCurrentInstance(); adfFacesContext.addPartialTarget(richTable);   return null; } The code shown above works for 99.5 % of all use cases that deal with multi row selection enabled ADF Faces tables, except for when users use the ctrl+a key to mark all rows for delete. Just to make sure I am clear: if you use ctrl+a to mark rows to perform any other operation on them – like bulk updating all rows for a specific attribute – then this works with the code shown above. Even for bulk row delete, any other mean of row selection (shift+click and multiple ctrl+click) works like a charm and the rows are deleted. So apparently it is the use of ctrl+a that causes the problem when deleting multiple rows of an ADF Faces table. To implement code that works for all table selection use cases, including the one to delete all table rows in one go, you use the code shown below. public void onRemoveSelectedTableRows(ActionEvent actionEvent) {   RichTable richTable = … get access to your table instance …   CollectionModel cm = (CollectionModel)richTable.getValue();   RowKeySet rowKeySet = (RowKeySet)richTable.getSelectedRowKeys();   Object[] rowKeySetArray = rowKeySet.toArray();      for (Object key : rowKeySetArray){               richTable.setRowKey(key);     JUCtrlHierNodeBinding rowData = (JUCtrlHierNodeBinding)cm.getRowData();                              rowData.getRow().remove();   }   AdfFacesContext adfFacesContext = AdfFacesContext.getCurrentInstance();          adfFacesContext.addPartialTarget(richTable); }

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• Adding Custom dialogs in Visual Studio Setup projects

  - by constant learner

  Hello All I need to develop a Visual Studio Setup Project for my application. As far as i see, i can use only a handful of preconfigured dialogs which i can use. Is there any way possible to use any custom dialogs in Visual Studio SetUp Project ? For ex: Whenever i start my setup, a dialog should be shown to the user prompting him to select a language for installation. The user then shall select a language based on his preference and the installation shall then commence thereafter. I hope i have made myself clear CL

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• Efficient existing rating system for multiplayer?

  - by Nikolay Kuznetsov

  I would like to add a rating for online version of a board game. In this game there are many game rooms each normally having 3-4 people. So I expect that player's rating adjustments (RA) should depends on Rating of opponents in the game room Number of players in game room and final place of a player Person gets rating increase if he plays more games and more frequently If a person leaves a game room (disconnect) before the game ends he should get punished with a high rating decrease I have found two related questions in here Developing an ELO like point system for a multiplayer gaming site Simplest most effective way to rank and measure player skill in a multi-player environment? Please, let me know what would be the most appropriate existing rating model to refer.

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• getSelection() by Double Click or manual selection is not the same

  - by sanceray3

  Hi all, I allow me to ask a question, because I have a little probleme with an function which returns me the parent of a selection. $('input[type=button].btn_transform').click(function(){ var selectionObj = getSelected();//Function which gives me selection var theParent=selectionObj.anchorNode.parentNode; alert (theParent); }) For example with this sentence : "the cat is <strong>gray</strong>." If I select manually the word "gray" and click on my button, the function returns me [object HTMLSpanElement]. But if I select the same word by double clicking, the function returns me [object HTMLParagraphElement]. Do you know why ? Thanks a lot.

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• Flex Dataprovider caching issue.

  - by prashanth

  I have two combobox controls. If i change combobox A then I am reading from xml and populating combobox B. The xml is loaded into memory in Application's creationComplete method. When I select values in combobox A and then open combobox B, I am seeing the values correctly, but when I deploy it on the server in a different machine (which is in a different subdomain), then my combobox B values are not cleared and are retained by old selection, when I select the combobox B, then it is getting refreshed. I am making the dataprovider = null for combobox b, and when I am assigning new collection then i am refreshing the arraycollection as well. But still the problem is not solved.

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• hibernate show real sql

  - by tommaso

  Hi all, if I set <property name="show_sql">true</property> in my hibernate.cfg.xml configuration file in the console I can see the sql. But it's not REAL sql... Can I see the SQL code that will be passed directly to database? Example: I see select this_.code from true.employee this_ where this_.code=? Can I see select employee.code from employee where employee.code=12 the real sql? thanks!

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• How to have combobox take data from a child datasource

  - by SkollSunman

  I am trying to have a datagridview with two comboboxes, a company name and a supplier account number. When a company name is selected the relevant supplier account numbers (a company can have more than one supplier account) should be filtered for that company in that row. I have a datagridview with two bindingsources: supplierBindingSource and companyBindingSource and the Supplier account combobox uses the supplierBindingSource for its datasource and company name uses the companyBindingSource for its datasource. A company can have a supplier and/or customer account so the supplierBindingSource is a child or a companyBindingSource. The supplier accounts correctly filter based on the selected company name however when another company name is selected in another row all the supplier accounts are filtered for that company. Saving still works properly, regardless of what the combo box show but currently it is very confusing for a user to select a supplier account when the labels don't show what is being saved. Is it possible to have only the selected row to filter based on the company name rather than every row? EDIT: Thanks to the answer from http://social.msdn.microsoft.com/Forums/windows/en-US/b23d9e8f-a00a-49ba-adf5-52d87c1b2890/parent-child-comboboxes-in-datagridview I have been able to make some progress. The supplier account gets filtered when the drop down box is selected and restored to the full list when selection is finished. However now I am trying to have the company selected (and not filtered) when a supplier account is selected. The issue I've run into now is that I can get the companyID (which is the valuemember for the company combobox) but I cannot select the appropriate company without just setting the value of the combobox to the companyID which displays the companyID instead of the company name. Is there a way to select the company using the companyID while preserving the displaymember/valuemember dynamic? EDIT 2: The wall of text may be off putting. Some code to help elucidate my issue DataGridViewComboBoxCell dgcb2 = (DataGridViewComboBoxCell)sdgvSalesOrderLines[cmbSupplierName.Index, e.RowIndex]; var companyID = col.FirstOrDefault(c => c.AccountID == Convert.ToInt32(dgcb.Value)).CompanyID; dgcb2.Value = companyID.toString(); The second line gets the companyID and that works just fine, the final line sets the combobox to display the companyID whereas I would like it to set the valuemember value to companyID so that it would display the corresponding company name. I can set the second line to give me the company name instead but if the value of the combobox isn't the companyID then the supplier account cannot filter based on the company selected.

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• Comparing COUNT values within a query?

  - by outsyncof

  I have the following tables in a relation: person(ssn,sex) employment(ssn,workweeksperyear) assume ssn is a key. My assignment was to do this: Given as input the number of weeks per year a person has worked, determine whether there are more males than females who work more weeks than the input value. SELECT COUNT(sex) AS NumMales FROM person WHERE sex = 'Male' AND ssn IN (SELECT ssn FROM employment WHERE workweeksperyear > 48); The above query gets me the number of males for an input value and I could do the same for number of females but how do I compare the 2 results? Any help will be greatly appreciated!

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• joins- how to pass the parameter in stored procedure to execute a join query

  - by Ranjana

  i have used joins to get datas from two tables under comman name. as SELECT userValidity.UserName, userValidity.ValidFrom,userValidity.ValidUpTo,userValidity.TotalPoints, persons.SenderID FROM userValidity INNER JOIN persons ON userValidity.Username=tbl_persons.Username but i need to execute this query with oly the username which i pass as parameter in stored procedure.. how to pass the username in stored procedure in this joins. alter procedure GetNameIDUserInformation ( @user varchar(max) ) as begin SELECT userValidity.UserName, userValidity.ValidFrom,userValidity.ValidUpTo,userValidity.TotalPoints, persons.SenderID FROM userValidity INNER JOIN persons ON userValidity.Username=tbl_persons.Username end in this SP, where i have to pass the user parameter to get the single row of my user record

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• Understanding SingleTableEntityPersister n QueryLoader

  - by Iapilgrim

  Hi, I have the Hibernate model @Cache(usage = CacheConcurrencyStrategy.NONE, region = SitesConstants.CACHE_REGION) public class Node extends StatefulEntity implements Inheritable, Cloneable { private Node _parent; private List<Node> _childNodes; .. } @Cache(usage = CacheConcurrencyStrategy.NONE, region = SitesConstants.CACHE_REGION) public class Page extends Node implements Defaultable, Securable { private RootZone _rootZone; ...... @OneToOne(fetch = FetchType.LAZY) @JoinColumn(name = "root_zone_id", insertable = false, updatable = false) public RootZone getRootZone() { return _rootZone; } public void setRootZone(RootZone rootZone) { if (rootZone != null) { rootZone.setPageId(this.getId()); _rootZone = rootZone; } } I want to get all pages ( call getSiteTree), so I using this query String hpql = "SELECT n FROM Node n "; See the trace I find Page.setRootZone(RootZone) line: 155 NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method] NativeMethodAccessorImpl.invoke(Object, Object[]) line: 39 DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25 Method.invoke(Object, Object...) line: 597 BasicPropertyAccessor$BasicSetter.set(Object, Object, SessionFactoryImplementor) line: 66 PojoEntityTuplizer(AbstractEntityTuplizer).setPropertyValues(Object, Object[]) line: 352 PojoEntityTuplizer.setPropertyValues(Object, Object[]) line: 232 SingleTableEntityPersister(AbstractEntityPersister).setPropertyValues(Object, Object[], EntityMode) line: 3580 TwoPhaseLoad.initializeEntity(Object, boolean, SessionImplementor, PreLoadEvent, PostLoadEvent) line: 152 QueryLoader(Loader).initializeEntitiesAndCollections(List, Object, SessionImplementor, boolean) line: 877 QueryLoader(Loader).doQuery(SessionImplementor, QueryParameters, boolean) line: 752 QueryLoader(Loader).doQueryAndInitializeNonLazyCollections(SessionImplementor, QueryParameters, boolean) line: 259 QueryLoader(Loader).doList(SessionImplementor, QueryParameters) line: 2232 QueryLoader(Loader).listIgnoreQueryCache(SessionImplementor, QueryParameters) line: 2129 QueryLoader(Loader).list(SessionImplementor, QueryParameters, Set, Type[]) line: 2124 QueryLoader.list(SessionImplementor, QueryParameters) line: 401 QueryTranslatorImpl.list(SessionImplementor, QueryParameters) line: 363 HQLQueryPlan.performList(QueryParameters, SessionImplementor) line: 196 SessionImpl.list(String, QueryParameters) line: 1149 QueryImpl.list() line: 102 QueryImpl.getResultList() line: 67 NodeDaoImpl.getSiteTree(long) line: 358 PageNodeServiceImpl.getSiteTree(long) line: 797 NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method] NativeMethodAccessorImpl.invoke(Object, Object[]) line: 39 DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25 Method.invoke(Object, Object...) line: 597 AopUtils.invokeJoinpointUsingReflection(Object, Method, Object[]) line: 307 JdkDynamicAopProxy.invoke(Object, Method, Object[]) line: 198 $Proxy100.getSiteTree(long) line: not available the calling setRootZone in Page makes Hibernate issue a hit to database. I don't want this. So my question is + Why query String hpql = "SELECT n FROM Node n "; issues un-expected trace logs like above. Why the query String hpql = "SELECT n.nodename FROM Node n " not? What is the mechanism behind? Note: Im using hibernate caching level 2. In case I don't want to see that trace logs. I mean I just get Node data only. How to do ? Thanks for your help. Sorry for my bad english :( Van

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• How can I do a right outer join where both tables have a where clause?

  - by cdeszaq

  Here's the scenario: I have 2 tables: CREATE TABLE dbo.API_User ( id int NOT NULL, name nvarchar(255) NOT NULL, authorization_key varchar(255) NOT NULL, is_active bit NOT NULL ) ON [PRIMARY] CREATE TABLE dbo.Single_Sign_On_User ( id int NOT NULL IDENTITY (1, 1), API_User_id int NOT NULL, external_id varchar(255) NOT NULL, user_id int NULL ) ON [PRIMARY] What I am trying to return is the following: is_active for a given authorization_key The Single_Sign_On_User.id that matches the external_id/API_User_id pair if it exists or NULL if there is no such pair When I try this query: SELECT Single_Sign_On_User.id, API_User.is_active FROM API_User LEFT OUTER JOIN Single_Sign_On_User ON Single_Sign_On_User.API_User_id = API_User.id WHERE Single_Sign_On_User.external_id = 'test_ext_id' AND API_User.authorization_key = 'test' where the "test" API_User record exists but the "test_ext_id" record does not, and with no other values in either table, I get no records returned. When I use: SELECT Single_Sign_On_User.id, API_User.is_active FROM API_User LEFT OUTER JOIN Single_Sign_On_User ON Single_Sign_On_User.API_User_id = API_User.id WHERE API_User.authorization_key = 'test' I get the results I expect (NULL, 1), but that query doesn't allow me to find the "test_ext_id" record if it exists but would give me all records associated with the "test" API_User record. How can I get the results I am after?

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• How do these user/userParam references relate to the Customer and Account lookups?

  - by marmalade

  In the following code example how do the user/userParam references relate to the Customer and Account lookups and what is the relationship between Customer and Account? // PersistenceManager pm = ...; Transaction tx = pm.currentTransaction(); User user = userService.currentUser(); List<Account> accounts = new ArrayList<Account>(); try { tx.begin(); Query query = pm.newQuery("select from Customer " + "where user == userParam " + "parameters User userParam"); List<Customer> customers = (List<Customer>) query.execute(user); query = pm.newQuery("select from Account " + "where parent-pk == keyParam " + "parameters Key keyParam"); for (Customer customer : customers) { accounts.addAll((List<Account>) query.execute(customer.key)); } } finally { if (tx.isActive()) { tx.rollback(); } }

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• How do these user/userParam references relate to the Customer and Account lookups?

  - by plath

  In the following code example how do the user/userParam references relate to the Customer and Account lookups and what is the relationship between Customer and Account? // PersistenceManager pm = ...; Transaction tx = pm.currentTransaction(); User user = userService.currentUser(); List<Account> accounts = new ArrayList<Account>(); try { tx.begin(); Query query = pm.newQuery("select from Customer " + "where user == userParam " + "parameters User userParam"); List<Customer> customers = (List<Customer>) query.execute(user); query = pm.newQuery("select from Account " + "where parent-pk == keyParam " + "parameters Key keyParam"); for (Customer customer : customers) { accounts.addAll((List<Account>) query.execute(customer.key)); } } finally { if (tx.isActive()) { tx.rollback(); } }

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• A Basic Thread

  - by Joe Mayo

  Most of the programs written are single-threaded, meaning that they run on the main execution thread. For various reasons such as performance, scalability, and/or responsiveness additional threads can be useful. .NET has extensive threading support, from the basic threads introduced in v1.0 to the Task Parallel Library (TPL) introduced in v4.0. To get started with threads, it's helpful to begin with the basics; starting a Thread. Why Do I Care? The scenario I'll use for needing to use a thread is writing to a file.  Sometimes, writing to a file takes a while and you don't want your user interface to lock up until the file write is done. In other words, you want the application to be responsive to the user. How Would I Go About It? The solution is to launch a new thread that performs the file write, allowing the main thread to return to the user right away.  Whenever the file writing thread completes, it will let the user know.  In the meantime, the user is free to interact with the program for other tasks. The following examples demonstrate how to do this. Show Me the Code? The code we'll use to work with threads is in the System.Threading namespace, so you'll need the following using directive at the top of the file: using System.Threading; When you run code on a thread, the code is specified via a method.  Here's the code that will execute on the thread: private static void WriteFile() { Thread.Sleep(1000); Console.WriteLine("File Written."); } The call to Thread.Sleep(1000) delays thread execution. The parameter is specified in milliseconds, and 1000 means that this will cause the program to sleep for approximately 1 second.  This method happens to be static, but that's just part of this example, which you'll see is launched from the static Main method.  A thread could be instance or static.  Notice that the method does not have parameters and does not have a return type. As you know, the way to refer to a method is via a delegate.  There is a delegate named ThreadStart in System.Threading that refers to a method without parameters or return type, shown below: ThreadStart fileWriterHandlerDelegate = new ThreadStart(WriteFile); I'll show you the whole program below, but the ThreadStart instance above goes in the Main method. The thread uses the ThreadStart instance, fileWriterHandlerDelegate, to specify the method to execute on the thread: Thread fileWriter = new Thread(fileWriterHandlerDelegate); As shown above, the argument type for the Thread constructor is the ThreadStart delegate type. The fileWriterHandlerDelegate argument is an instance of the ThreadStart delegate type. This creates an instance of a thread and what code will execute, but the new thread instance, fileWriter, isn't running yet. You have to explicitly start it, like this: fileWriter.Start(); Now, the code in the WriteFile method is executing on a separate thread. Meanwhile, the main thread that started the fileWriter thread continues on it's own.  You have two threads running at the same time. Okay, I'm Starting to Get Glassy Eyed. How Does it All Fit Together? The example below is the whole program, pulling all the previous bits together. It's followed by its output and an explanation. using System; using System.Threading; namespace BasicThread { class Program { static void Main() { ThreadStart fileWriterHandlerDelegate = new ThreadStart(WriteFile); Thread fileWriter = new Thread(fileWriterHandlerDelegate); Console.WriteLine("Starting FileWriter"); fileWriter.Start(); Console.WriteLine("Called FileWriter"); Console.ReadKey(); } private static void WriteFile() { Thread.Sleep(1000); Console.WriteLine("File Written"); } } } And here's the output: Starting FileWriter Called FileWriter File Written So, Why are the Printouts Backwards? The output above corresponds to Console.Writeline statements in the program, with the second and third seemingly reversed. In a single-threaded program, "File Written" would print before "Called FileWriter". However, this is a multi-threaded (2 or more threads) program.  In multi-threading, you can't make any assumptions about when a given thread will run.  In this case, I added the Sleep statement to the WriteFile method to greatly increase the chances that the message from the main thread will print first. Without the Thread.Sleep, you could run this on a system with multiple cores and/or multiple processors and potentially get different results each time. Interesting Tangent but What Should I Get Out of All This? Going back to the main point, launching the WriteFile method on a separate thread made the program more responsive.  The file writing logic ran for a while, but the main thread returned to the user, as demonstrated by the print out of "Called FileWriter".  When the file write finished, it let the user know via another print statement. This was a very efficient use of CPU resources that made for a more pleasant user experience. Joe

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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• Cant create 2nd textbox

  - by okinaw55

  Having problems with this code and cant figure out why. It works fine the first time through but crashes with a Parameter is not Valid error the 2nd time on this line. Dim tbx As TextBox = New Windows.Forms.TextBox Any help is appreciated. Dim tbx As TextBox = New Windows.Forms.TextBox tbx.Name = tbxName tbx.Size = New System.Drawing.Size(55, 12) tbx.BorderStyle = BorderStyle.None tbx.TextAlign = HorizontalAlignment.Center Using f As Font = tbx.Font tbx.Font = New Font(f.FontFamily, 8, FontStyle.Bold) End Using tbx.Location = New System.Drawing.Point(xCords, 44) Select Case tbx.Name Case "tbxBulk01" : tbx.Text = Bulk01Label Case "tbxBulk02" : tbx.Text = Bulk02Label End Select Me.Controls.Add(tbx) Stack trace as follows. at System.Drawing.Font.GetHeight(Graphics graphics) at System.Drawing.Font.GetHeight() at System.Drawing.Font.get_Height() at System.Windows.Forms.Control.get_FontHeight() at System.Windows.Forms.TextBoxBase.get_PreferredHeight() at System.Windows.Forms.TextBoxBase.get_DefaultSize() at System.Windows.Forms.Control..ctor(Boolean autoInstallSyncContext) at System.Windows.Forms.TextBoxBase..ctor() at System.Windows.Forms.TextBox..ctor()

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• How To Get A Field Value Based On The Max Of Another Field In VFP v8.0

  - by DaveB

  So, I have a table and I want to get the value from one field in the record with the greatest DateTime() value in another field and where still another field is equal to a certain value. Example data: Balance Created MeterNumber 7924.252 02/02/2010 10:31:48 AM 2743800 7924.243 02/02/2010 11:01:37 AM 2743876 7924.227 02/02/2010 03:55:50 PM 2743876 I want to get the balance for a record with the greatest created datetime for a specific meter number. In VFP 7 I can use: SELECT a.balance ,MAX(a.created) FROM MyTable a WHERE a.meternumber = '2743876' But, in the VFP v8.0 OleDb driver I am using in my ASP.NET page I must conform to VFP 8 which says you must have a GROUP BY listing each non aggregate field listed in the SELECT. This would return a record for each balance if I added GROUP BY a.balance to my query. Yes, I could issue a SET ENGINEBEHAVIOR 70 but I wanted to know if this could be done without having to revert to a previous version?

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• has_many :through when join table doesn't contain FK to both tables

  - by seth.vargo

  I have a structure that isn't really a has_many :through example, but I'd like it to behave like one: # user.rb belongs_to :blog has_many :posts # post.rb belongs_to :user # blog.rb has_many :users has_many :posts, :through => :users # this obviously doesn't work becase # both FKs aren't in the blogs table I want to get ALL posts for a blog in an array. I'm aware that I can do this with Ruby using each or getting fancy with collect, but I'd like to let SQL do the work. Can someone explain how I can set up my models in a way that lets me call @blog.posts using SQL, not Ruby? Edit: I know in SQL I can write something like: SELECT * FROM posts WHERE posts.user_id IN ( SELECT users.id FROM users WHERE users.blog_id = 7 ) which obviously shows two queries are needed. I don't think this is possible with a join, but I'm not totally sure. It's obvious that a subquery is needed, but how do I get rails to build that subquery with ARel instead of having to return and use Ruby to loop and collect and such?

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• Using COALESCE to avoid dynamic SQL ?

  - by krul

  I would like to use following sql to avoid constructing sql dynamically: SELECT CommentID, Comment, FROM Comments --if Author id is not null then filter upon author id otherwise get all comments (ignore author id) WHERE AuthorID LIKE COALESCE(@AuthorId, '%') --if comment type is present filter upon it, otherwise get all comments (ignore comment type condition) AND CommentType LIKE COALESCE(@CommentType, '%') I want to know is that safe way to approach this problem? EDIT: Here is final code that satisfy my need to ignore search parameter if is null and applied it if is present: SELECT CommentID, Comment, FROM Comments --if @AuthorId is not null then filter upon @AuthorId otherwise get all comments (ignore author id) WHERE AuthorID = COALESCE(@AuthorId, AuthorID) --if @CommentType is present filter upon it, otherwise get all comments (ignore comment type condition) AND CommentType = COALESCE(@CommentType, CommentType)

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• Best Way to Generate Unique and consecutives numbers in Oracle

  - by RRUZ

  I need to generate unique and consecutive numbers (for use on an invoice), in a fast and reliable way. currently use a Oracle sequence, but in some cases generated numbers are not consecutive because of exceptions that may occur. I thought a couple of solutions to manage this problem, but neither of they convincing me. What solution do you recommend? Use a select max () SELECT MAX (NVL (doc_num, 0)) +1 FROM invoices Use a table to store the last number generated for the invoice. UPDATE docs_numbers SET last_invoice = last_invoice + 1 Another Solution?

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• searching between dates in MYSQL in this format 03/17/10.11:22:45

  - by Kelso

  I have a script that automatically populates a mysql database with data every hour. It populates the date field like 03/17/10.12:34:11 and so on. I'm working on pulling data based on 1 day at a time from a search script. If i use select * from call_logs where call_initiated between '03/17/10.12:00:00' and '03/17/10.13:00:00' it works, but when I try to add the rest of the search params, it ignores the call_initiated field. select * from call_logs where caller_dn='2x9xxx0000' OR called_dn='2x9xxx0000' AND call_initiated between '03/17/10.12:00:00' and '03/17/10.13:00:00' ^-- I x'd out a couple of the numbers. I've also tried without the between function, and used = <= to pull the records, but have the same results. Im sure its an oversight, thanks in advance.

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