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  • Regarding Visual C# MenuItem: Where does the NullReference come from?

    - by Thomas
    Hi All. I have a problem creating MenuItems for a TreeView dynamically: here is the (simplified)code i'm using. public class CTM : TreeNode, IComparable, IComparable<CTM> { public CTM(CTMProvider provider) { this.provider = provider; this.manager = provider.manager; this.IEEEAddress = provider.IEEEAddress; this.endpoint = provider.state._conn.RemoteEndPoint; this.Text = String.Format("CTM: {0} {0}", IEEEAddress, ((System.Net.IPEndPoint)endpoint).ToString()); try { MenuItem meni = System.EventHandler(this.provider.Disconnect)); this.ContextMenu.MenuItems.Add(meni); } catch { Trace.TraceError("Could not create menu item!"); } } } This code always triggers the catch clause with a NullReferenceException. Any Ideas?

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  • Matching of tuples

    - by Jack
    From what I understood I can use pattern-matching in a match ... with expression with tuples of values, so something like match b with ("<", val) -> if v < val then true else false | ("<=", val) -> if v <= val then true else false should be correct but it gives me a syntax error as if the parenthesis couldn't be used: File "ocaml.ml", line 41, characters 14-17: Error: Syntax error: ')' expected File "ocaml.ml", line 41, characters 8-9: Error: This '(' might be unmatched referring on first match clause.. Apart from that, can I avoid matching strings and applying comparisons using a sort of eval of the string? Or using directly the comparison operator as the first element of the tuple?

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  • How to perform a non-polymorphic HQL query in Hibernate?

    - by Eli Acherkan
    Hi all, I'm using Hibernate 3.1.1, and in particular, I'm using HQL queries. According to the documentation, Hibernate's queries are polymorphic: A query like: from Cat as cat returns instances not only of Cat, but also of subclasses like DomesticCat. How can I query for instances of Cat, but not of any of its subclasses? I'd like to be able to do it without having to explicitly mention each subclass. I'm aware of the following options, and don't find them satisfactory: Manually filtering the instances after the query, OR: Manually adding a WHERE clause on the discriminator column. It would make sense for Hibernate to allow the user to decide whether a query should be polymorphic or not, but I can't find such an option. Thanks in advance!

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  • SQL Server Query Editors - any that warn of number of rows to be changed?

    - by ciaranarcher
    We're using SQL Server 2000 Query Analyser, and one issue we have is that very occasionally, when a user is updating our live database, they insert the incorrect/no(!) where clause. I know, not good, but it happens. Are there any editors that will warn of the number of rows that might be changed (if that is even possible) or even a way to configure an editor, if it is connected to a certain database, to prompt for confirmation before the query is run? We have a way to recover our data in the cases where we run an incorrect query, but it takes time, and I'm just seeing if there are any ways to catch the error, or at least give the user a second chance. Thanks in advance.

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  • Find the highest number of occurences in a column in SQL

    - by Ronnie
    Given this table: Order custName description to_char(price) A desa $14 B desb $14 C desc $21 D desd $65 E dese $21 F desf $78 G desg $14 H desh $21 I am trying to display the whole row where prices have the highest occurances, in this case $14 and $21 I believe there needs to be a subquery. So i started out with this: select max(count(price)) from orders group by price which gives me 3. after some time i didn't think that was helpful. i believe i needed the value 14 and 21 rather the the count so i can put that in the where clause. but I'm stuck how to display that. any help?

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  • SQL Group By equivalent

    - by MikeB
    Pretend I have a cupcake_rating table: id | cupcake | delicious_rating -------------------------------------------- 1 | Strawberry | Super Delicious 2 | Strawberry | Mouth Heaven 3 | Blueberry | Godly 4 | Blueberry | Super Delicious I want to find all the cupcakes that have a 'Super Delicious' AND 'Mouth Heaven' rating. I feel like this is easily achievable using a group by clause and maybe a having. I was thinking: select distinct(cupcake) from cupcake_rating group by cupcake having delicious_rating in ('Super Delicious', 'Mouth Heaven') I know I can't have two separate AND statements. I was able to achieve my goal using: select distinct(cupcake) from cupcake_rating where cupcake in ( select cupcake from cupcake_rating where delicious_rating = 'Super Delicious' ) and cupcake in ( select cupcake from cupcake_rating where delicious_rating = 'Mouth Heaven' ) This will not be satisfactory because once I add a third type of rating I am looking for, the query will take hours (there are a lot of cupcake ratings).

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  • The use of GROUP BY in MySQL

    - by Gustav Bertram
    I'm fishing for a comprehensive and canonical answer for the typical "mysql group by?" question. Here is some sample data: TABLE A +------+------+----------+-----+ | id | foo | bar | baz | +------+------+----------+-----+ | 1 | 1 | hello | 42 | | 2 | 0 | apple | 96 | | 3 | 20 | boot | 11 | | 4 | 31 | unicorn | 99 | | 5 | 19 | pumpkin | 11 | | 6 | 88 | orange | 13 | +------+------+----------+-----+ TABLE B +------+------+ | id | moo | +------+------+ | 1 | 1 | | 2 | 99 | | 3 | 11 | +------+------+ Demonstrate and explain the correct use of the GROUP BY clause in MySQL. Touch upon the following points: The use of MIN, MAX, SUM, AVG The use of HAVING Grouping by date, and ranges of dates Grouping with an ORDER BY Grouping with a JOIN Grouping on multiple columns Bonus points for references to other great answers, the MySQL online manual, and online tutorials on GROUP BY.

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  • How can one extract rdf:about or rdf:ID properties from triples using SPARKQL?

    - by lennyks
    It seemed a trivial matter at the beginning but so far I had not managed to get unique identifier for a given resource using SPARKQL. What I mean is given, let say, rdf:Description rdf:about="http://..." and then some properties identifying this resource, what I want to do is to first find this very resource and then retrieve all the triples given some uri. I have tried naive approaches by writing statements in a WHERE clause such as ?x rdf:about ?y and ?x rdfs:about ?y. I hope I am being precise.

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  • C# Compiler should give warning but doesn't?

    - by Cristi Diaconescu
    Someone on my team tried fixing a 'variable not used' warning in an empty catch clause. try { ... } catch (Exception ex) { } - gives a warning about ex not being used. So far, so good. The fix was something like this: try { ... } catch (Exception ex) { string s = ex.Message; } Seeing this, I thought "Just great, so now the compiler will complain about s not being used." But it doesn't! There are no warnings on that piece of code and I can't figure out why. Any ideas? PS. I know catch-all clauses that mute exceptions are a bad thing, but that's a different topic. I also know the initial warning is better removed by doing something like this, that's not the point either. try { ... } catch (Exception) { } or try { ... } catch { }

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  • SQL GROUP BY with "default values"

    - by Christoph Schiessl
    I'm trying to create SELECT statement with a GROUP BY clause, which should return "default values". Imagine the following simple MySQL table: CREATE TABLE `tracker` ( `id` INTEGER PRIMARY KEY auto_increment, `date` DATETIME NOT NULL, `customer_id` INTEGER NOT NULL ); The table contains only one record: INSERT INTO `tracker` (`date`, `customer_id`) VALUES('2010-05-03', 1); After wards I'm executing the following SQL query: SELECT DATE(`date`), COUNT(customer_id) FROM tracker WHERE DATE(`date`) >= '2010-05-01' AND DATE(`date`) <= '2010-05-05' GROUP BY DATE(`date`) ORDER BY DATE(`date`); And get the expected result set: +----+---------------------+-------------+ | id | date | customer_id | +----+---------------------+-------------+ | 1 | 2010-05-10 00:00:00 | 1 | +----+---------------------+-------------+ However, I would like the result set to look like this: +--------------+--------------------+ | DATE(`date`) | COUNT(customer_id) | +--------------+--------------------+ | 2010-05-01 | 0 | | 2010-05-02 | 0 | | 2010-05-03 | 1 | | 2010-05-04 | 0 | | 2010-05-05 | 0 | +--------------+--------------------+ Is it possible to achieve this behavior?

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  • JDO in Google App Engine: order of keys in unowned one-to-many relationship

    - by Kel
    I'm implementing web application with JDO in Google App Engine. According to documentation, in owned one-to-many relationships, order of elements in "owner" object collection is determined either by automatically created index field, or by information given in explicit ordering clause. For example: @PersistenceCapable public class Person { // ... @Order(extensions = @Extension(vendorName="datanucleus", key="list-ordering", value="country asc, city asc")) private List<ContactInfo> contacts = new List<ContactInfo>(); In unowned relationships, "owner" object contains collection of keys of "nested" objects, for example: @PersistenceCapable public class Author { // ... @Persistent private List<Key> books; Is order of keys preserved, if I use List<Key> collection in "owner" object for storing keys of "nested" elements? I could not find answer neither in JDO relationships article, nor in Data Classes article :(

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  • xquery expression to return a link text only if it contains within it a specific string

    - by Arvind
    I want to extract some links from a XML document (links are in same format as on html pages). Now for eg a link is "http://xyz.com/start/tyu/a.html" and another is "http://ert.com/tyu/b.html" while a third link is "http://asdf.com/ghjk/c.html" From the above 3 links (which I have with me using a for clause in a FLWOR expression)...I want only the links which contain within them a string "tyu" to be selected-- I thought of using substring for this, but substring requires start and end positions to be specified- whereas in my scenario, I dont know at which position the desired string will be. How do I do substring matching in such a scenario, i.e. where exact position for occurrence of substring, is not known? I can use XQuery 1.0 for this purpose. Finally, I want to extract the link URL, as well as link text...

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  • $where in mongodb web shell not working

    - by Bravo
    i have the below set of test documents which i inserted in to the mongodb and when i use to query the db using the $where get the below exception Error: database error: $where query, but no script engine Any idea why the $where clause not working test data : db.things.save({ "_id" : 1, "domainName" : "test11.com", "hosting" : "hostgator.com" }) db.things.save({ "_id" : 2, "domainName" : "test2.com", "hosting" : "aws.amazon.com"}) db.things.save({ "_id" : 3, "domainName" : "test3.com", "hosting" : "aws.amazon.com" }) db.things.save({ "_id" : 4, "domainName" : "test4.com", "hosting" : "hostgator.com" }) db.things.save({ "_id" : 5, "domainName" : "test5.com", "hosting" : "aws.amazon.com" }) db.things.save({ "_id" : 6, "domainName" : "test6.com", "hosting" : "cloud.google.com" }) db.things.save({ "_id" : 7, "domainName" : "test7.com", "hosting" : "aws.amazon.com" }) db.things.save({ "_id" : 8, "domainName" : "test8.com", "hosting" : "hostgator.com" }) db.things.save({ "_id" : 9, "domainName" : "test9.com", "hosting" : "cloud.google.com" }) db.things.save({ "_id" : 10, "domainName" : "test10.com", "hosting" : "godaddy.com" }) query used : db.things.find( { $where: "this.domainName == 'test11.com'" } );

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  • How to pass an xpath into an xquery function declaration

    - by topmulch
    Hi all, I use Apache Tomcat's Exist DB as an XML database and am trying to construct a sequence by passing the following xpath, defined in FLWOR's 'let' clause: $xpath := $root/second/third into a locally defined function declaration, like so: declare function local:someFunction($uuid as xs:string?, $xpath as xs:anyAtomicType?) { let $varOne := $xpath/fourth[@uuid = $uuid]/fifthRight let $varTwo := $xpath/fourth[@uuid = $uuid]/fifthLeft let $combined := ($varOne,$varTwo) return $combined }; Of course, when entering this in the exist xquery sandbox, I get Type: xs:anyAtomicType is not defined. What should I use in place of it, or should I do this a different way? Thanks in advance for any suggestions.

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  • How to catch exception on RollBack

    - by Jagd
    What is the best way to implement error handling for a SqlTransaction RollBack that already exists within a catch clause? My code is roughly like this: using (SqlConnection objSqlConn = new SqlConnection(connStr)) { objSqlConn.Open(); using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) { try { // code // more code // and more code } catch (Exception ex) { // What happens if RollBack() has an exception? objSqlTrans.Rollback(); throw ex; } } } I believe that my application had an exception in the try block, which in turn was caught in the catch block and then the RollBack was attempted. However, the error that I'm seeing says something about a SqlTransaction.ZombieCheck(), which is making me wonder if the RollBack() itself threw an exception as well. So, do I need to implement some type of error handling at the RollBack()? How do I do that and manage to hold on to the exception that put the execution into the catch block in the first place?

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  • Removing duplicate SQL records to permit a unique key

    - by j pimmel
    I have a table ('sales') in a MYSQL DB which should have rightfully have had a unique constraint enforced to prevent duplicates. To first remove the dupes and set the constraint is proving a bit tricky. Table structure (simplified): 'id (unique, autoinc)' product_id The goal is to enforce uniqueness for product_id. The de-duping policy I want to apply is to remove all duplicate records except the most recently created, eg: the highest id Or to put another way, I would like to delete duplicate records, excluding the ids matched by the following query: select id from sales s inner join (select product_id, max(id) as maxId from sales group by product_id having count(product_id) > 1) groupedByProdId on s.product_id and s.id = groupedByProdId.maxId I've struggled with this on two fronts - writing the query to select the correct records to delete and then also the constraint in MYSQL where a subselect FROM clause of a DELETE cannot reference the same table from which data is being removed.

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  • Cakephp, Retreive Data for HABTM Models using find

    - by user298079
    I am new to cakephp and I'm trying to accomplish something that should be relatively easy. I have 2 models projects & categories bind by HABTM relationship. I am trying to perform the following query - find all projects that belong to a category $projects = $this->Project->find('all', array('conditions' => array('Category.slug' => $category))); However when I'm doing so it generates an SQL error: SQL Error: 1054: Unknown column 'Category.slug' in 'where clause' What am I doing wrong??

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  • ajax and servlet

    - by kawtousse
    Hi everyone I am using ajax to send a value to a servlet with that parameter value I must display a table HTML. from my JSP when sending with following: xhr.open("POST","ServletImputOPC",true); xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded'); var unit =document.getElementById('unit').value; xhr.send("t[0]="+t[0]); it returns the clause in my servlet correctly witch is: parameter received:Nameof my parameter. that is improve that the servlet receive the parameter. But when using it in the servlet it return a null value. So the problem that the servlet return the parameter received but did not able to use it. What should I do to resolve it. Many thinks.

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  • lambda expression for a query on two tables that returns records from one table

    - by peetee
    I have two tables TableA (articles) int id int Type string name and TableB (compatibles) int linked_ID int tableA_ID TableA records: id=1, Type=0, name="ArticleA" id=2, Type=1, name="ArticleB" id=3, Type=2, name="ArticleC" id=4, Type=1, name="ArticleD" TableB records: linked_ID= 1, tableA_ID=2 linked_ID= 1, tableA_ID=3 linked_ID= 1, tableA_ID=4 TableB has a list of arcicels that are compatible to a certain article. I am quite new to queries (didn't need them in my projects yet). But as C# and WPF allow some pretty cool automation with Binding I would like to add a binding that returns the following: Give me all articles that are of Type 1 and compatible to my selected article (id=1). The simple part of it works well (articles has a list of all articles): private ObservableCollection<Article> _articles = new ObservableCollection<Article>(); [fill it with the available articles] and then: comboBoxArticles.ItemsSource = _articles.AsBindable().Where( c => c.Typ == 0 ); How can I extend the Where clause to query another table? Thanks a lot in advance.

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  • Left Join not returning all rows

    - by DisgruntledGoat
    I have this query in MySQL: SELECT pr.*, pr7.value AS `room_price_high` FROM `jos_hp_properties` pr LEFT OUTER JOIN `jos_hp_properties2` pr7 ON pr7.property=pr.id WHERE pr7.field=23 The jos_hp_properties table has 27 rows but the query only returns one. Based on this question I think it may be because of the WHERE clause. The jos_hp_properties2 table has fields id, property, field, value, where field is a foreign key to a third table (which I don't need to get data from). Is there a way to select all the rows from the first table, including the value from table #2 where the field is 23 (or NULL if there is no field 23)?

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  • How to dynamically order many-to-many relationship in JPA or HQl?

    - by Indrek
    I have a mapping like this: @ManyToMany(cascade = CascadeType.PERSIST) @JoinTable( name="product_product_catalog", joinColumns={@JoinColumn(name="product_catalog", referencedColumnName="product_catalog")}, inverseJoinColumns={@JoinColumn(name="product", referencedColumnName="product")}) public List<Product> products = new ArrayList<Product>(); I can fetch the products for the catalog nicely, but I can't (dynamically) order the products. How could I order them? I probably have to write a many-to-many HQL query with the order-by clause? I though of passing the orderBy field name string to the query, or is there a better solution? Tables are: products, product_catalog, product_product_catalog (associative table) P.S. Using Play! Framework JPASupport for my entities.

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  • Reuse select query in a procedure in Oracle

    - by Jer
    How would I store the result of a select statement so I can reuse the results with an in clause for other queries? Here's some pseudo code: declare ids <type?>; begin ids := select id from table_with_ids; select * from table1 where id in (ids); select * from table2 where id in (ids); end; ... or will the optimizer do this for me if I simply put the sub-query in both select statements?

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  • Prolog: using the sort/2 predicate

    - by Øyvind Hauge
    So I'm trying to get rid of the wrapper clause by using the sort library predicate directly inside split. What split does is just generating a list of numbers from a list that looks like this: [1:2,3:2,4:6] ---split-- [1,2,3,2,4,6]. But the generated list contains duplicates, and I don't want that, so I'm using the wrapper to combine split and sort, which then generates the desired result: [1,2,3,4,6]. I'd really like to get rid of the wrapper and just use sort within split, however I keep getting "ERROR: sort/2: Arguments are not sufficiently instantiated." Any ideas? Thanks :) split([],[]). split([H1:H2|T],[H1,H2|NT]) :- split(T,NT). wrapper(L,Processed) :- split(L,L2), sort(L2,Processed).

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  • Invalid SQL Query

    - by svovaf
    I have the next query that in my opinion is a valid one, but I keep getting error telling me that there is a proble on "WHERE em.p4 = ue.p3" - Unknown column 'ue.p3' in 'where clause'. This is the query: SELECT DISTINCT ue.p3 FROM table1 AS ue INNER JOIN table2 AS e ON ue.p3 = e.p3 WHERE EXISTS( SELECT 1 FROM ( SELECT (COUNT(*) >= 1) AS MinMutual FROM table4 AS smm WHERE smm.p1 IN ( SELECT sem.p3 FROM table3 AS sem INNER JOIN table2 AS em ON sem.p3 = em.p3 WHERE em.p4 = ue.p3 AND sem.type = 'friends' AND em.p2 = 'normal' ) AND smm.p5 IN ( 15000,15151 ) ) AS Mutual WHERE Mutual.MinMutual = TRUE) LIMIT 11 If I execute the sub-query which is inside the EXISTS function, everything is O.K. PLEASE HELP!

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  • Filter rows from Cursor so they don't show up in ListView

    - by Richard
    I have a Cursor that returns rows I use with a SimpleCursorAdapter to populate a ListView. I would like to filter some of the rows so they don't get displayed in my ListView. I use the data from the rows elsewhere in my Activity so I don't want to change my SQL to filter them with a WHERE clause. What is the best way to keep a row from being displaying in my ListView? Ideally I would check a column in my row and then only add rows to the ListView that satisfy a condition.

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