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  • should i advocate migrating from access to (my)sql

    - by HotOil
    Hi: We have a windows MFC app that is written against an access database on a company server. The db is not that big: 19 MB. There are at most 2-3 users accessing it at any one time. It is used in a factory environment where access speed (or lack thereof) over the intranet becomes noticeable as it is part of the manufacturing time for our widgets. The scenario is this: as each widget is completed, it gets a record in the db.. by the end of the year, the db is larger and searching for a record takes longer and longer. The solution so far has been to manually move older records to an archival table about once a year. We are reworking other portions of this app right now, and it would be a good time to move to another db if we are going to do it. It is my understanding that if we were using sql, the search time would not go up as the table gets bigger because the entire .mdb does not have to be sent over the network each time. Is this correct? Does anyone have any insight about whether it could be worth it to go to the trouble (time and money) of migrating to a new db, or should I just add more functionality to the application we have now, and maybe automatically purge the older records from time to time, and add additional facilities to the app to get at the older records when needed? Thanks for any wisdom you can share..

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  • delete row from result set in web sql with javascript

    - by Kaijin
    I understand that the result set from web sql isn't quite an array, more of an object? I'm cycling through a result set and to speed things up I'd like to remove a row once it's been found. I've tried "delete" and "splice", the former does nothing and the latter throws an error. Here's a piece of what I'm trying to do, notice the delete on line 18: function selectFromReverse(reverseRay,suggRay){ var reverseString = reverseRay.toString(); db.transaction(function (tx) { tx.executeSql('SELECT votecount, comboid FROM counterCombos WHERE comboid IN ('+reverseString+') AND votecount>0', [], function(tx, results){ processSelectFromReverse(results,suggRay); }); }, function(){onError}); } function processSelectFromReverse(results,suggRay){ var i = suggRay.length; while(i--){ var j = results.rows.length; while(j--){ console.log('searching'); var found = 0; if(suggRay[i].reverse == results.rows.item(j).comboid){ delete results.rows.item(j); console.log('found'); found++; break; } } if(found == 0){ console.log('lost'); } } }

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  • Group Specific set of data by Day

    - by Jacques444
    Need to get a certian subgroup of data per day (Seperated by weekday) For example Select weekday,bla,blabla,blablabla from dbo.blabla where bla = @StartDate and bla <=@endDate I need the output to be: Monday bla blabla blablabla Tuesday bla blabla blablabla If someone could help me that would be awesome. Thanks & Regards Jacques

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  • Getting the first of a GROUP BY clause in SQL

    - by Michael Bleigh
    I'm trying to implement single-column regionalization for a Rails application and I'm running into some major headaches with a complex SQL need. For this system, a region can be represented by a country code (e.g. us) a continent code that is uppercase (e.g. NA) or it can be NULL indicating the "default" information. I need to group these items by some relevant information such as a foreign key (we'll call it external_id). Given a country and its continent, I need to be able to select only the most specific region available. So if records exist with the country code, I select them. If, not I want a records with the continent code. If not that, I want records with a NULL code so I can receive the default values. So far I've figured that I may be able to use a generated CASE statement to get an arbitrary sort order. Something like this: SELECT *, CASE region WHEN 'us' THEN 1 WHEN 'NA' THEN 2 ELSE 3 END AS region_sort FROM my_table WHERE region IN ('us','NA') OR region IS NULL GROUP BY external_id ORDER BY region_sort The problem is that without an aggregate function the actual data returned by the GROUP BY for a given row seems to be untameable. How can I massage this query to make it return only the first record of the region_sort ordered groups?

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  • What are the advantages of a query using a derived table(s) over a query not using them?

    - by AspOnMyNet
    I know how derived tables are used, but I still can’t really see any real advantages of using them. For example, in the following article http://techahead.wordpress.com/2007/10/01/sql-derived-tables/ the author tried to show benefits of a query using derived table over a query without one with an example, where we want to generate a report that shows off the total number of orders each customer placed in 1996, and we want this result set to include all customers, including those that didn’t place any orders that year and those that have never placed any orders at all( he’s using Northwind database ). But when I compare the two queries, I fail to see any advantages of a query using a derived table ( if nothing else, use of a derived table doesn't appear to simplify our code, at least not in this example): Regular query: SELECT C.CustomerID, C.CompanyName, COUNT(O.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN Orders O ON C.CustomerID = O.CustomerID AND YEAR(O.OrderDate) = 1996 GROUP BY C.CustomerID, C.CompanyName Query using a derived table: SELECT C.CustomerID, C.CompanyName, COUNT(dOrders.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN (SELECT * FROM Orders WHERE YEAR(Orders.OrderDate) = 1996) AS dOrders ON C.CustomerID = dOrders.CustomerID GROUP BY C.CustomerID, C.CompanyName Perhaps this just wasn’t a good example, so could you show me an example where benefits of derived table are more obvious? thanx

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  • Convert SQL to LINQ in MVC3 with Ninject

    - by Jeff
    I'm using MVC3 and still learning LINQ. I'm having some trouble trying to convert a query to LINQ to Entities. I want to return an employee object. SELECT E.EmployeeID, E.FirstName, E.LastName, MAX(EO.EmployeeOperationDate) AS "Last Operation" FROM Employees E INNER JOIN EmployeeStatus ES ON E.EmployeeID = ES.EmployeeID INNER JOIN EmployeeOperations EO ON ES.EmployeeStatusID = EO.EmployeeStatusID INNER JOIN Teams T ON T.TeamID = ES.TeamID WHERE T.TeamName = 'MyTeam' GROUP BY E.EmployeeID, E.FirstName, E.LastName ORDER BY E.FirstName, E.LastName What I have is a few tables, but I need to get only the newest status based on the EmployeeOpertionDate. This seems to work fine in SQL. I'm also using Ninject and set my query to return Ienumerable. I played around with the group by option but it then returns IGroupable. Any guidance on converting and returning the property object type would be appreciated. Edit: I started writing this out in LINQ but I'm not sure how to properly return the correct type or cast this. public IQueryable<Employee> GetEmployeesByTeam(int teamID) { var q = from E in context.Employees join ES in context.EmployeeStatuses on E.EmployeeID equals ES.EmployeeID join EO in context.EmployeeOperations on ES.EmployeeStatusID equals EO.EmployeeStatusID join T in context.Teams on ES.TeamID equals T.TeamID where T.TeamName == "MyTeam" group E by E.EmployeeID into G select G; return q; } Edit2: This seems to work for me public IQueryable<Employee> GetEmployeesByTeam(int teamID) { var q = from E in context.Employees join ES in context.EmployeeStatuses on E.EmployeeID equals ES.EmployeeID join EO in context.EmployeeOperations.OrderByDescending(eo => eo.EmployeeOperationDate) on ES.EmployeeStatusID equals EO.EmployeeStatusID join T in context.Teams on ES.TeamID equals T.TeamID where T.TeamID == teamID group E by E.EmployeeID into G select G.FirstOrDefault(); return q; }

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  • Two radically different queries against 4 mil records execute in the same time - one uses brute force.

    - by IanC
    I'm using SQL Server 2008. I have a table with over 3 million records, which is related to another table with a million records. I have spent a few days experimenting with different ways of querying these tables. I have it down to two radically different queries, both of which take 6s to execute on my laptop. The first query uses a brute force method of evaluating possibly likely matches, and removes incorrect matches via aggregate summation calculations. The second gets all possibly likely matches, then removes incorrect matches via an EXCEPT query that uses two dedicated indexes to find the low and high mismatches. Logically, one would expect the brute force to be slow and the indexes one to be fast. Not so. And I have experimented heavily with indexes until I got the best speed. Further, the brute force query doesn't require as many indexes, which means that technically it would yield better overall system performance. Below are the two execution plans. If you can't see them, please let me know and I'll re-post then in landscape orientation / mail them to you. Brute-force query: Index-based exception query: My question is, based on the execution plans, which one look more efficient? I realize that thing may change as my data grows.

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  • SQL: Find the max record per group

    - by user319088
    I have one table, which has three fields and data. Name , Top , Total cat , 1 , 10 dog , 2 , 7 cat , 3 , 20 horse , 4 , 4 cat , 5 , 10 dog , 6 , 9 I want to select the record which has highest value of Total for each Name, so my result should be like this: Name , Top , Total cat , 3 , 20 horse , 4 , 4 Dog , 6 , 9 I tried group by name order by total, but it give top most record of group by result. Can anyone guide me, please?

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  • What could possibly be different between the table in a DataContext and an IQueryable<Table> when do

    - by Nate Bross
    I have a table, where I need to do a case insensitive search on a text field. If I run this query in LinqPad directly on my database, it works as expected Table.Where(tbl => tbl.Title.Contains("StringWithAnyCase") In my application, I've got a repository which exposes IQueryable objects which does some initial filtering and it looks like this var dc = new MyDataContext(); public IQueryable<Table> GetAllTables() { var ret = dc.Tables.Where(t => t.IsActive == true); return ret; } In the controller (its an MVC app) I use code like this in an attempt to mimic the LinqPad query: var rpo = new RepositoryOfTable(); var tables = rpo.GetAllTables(); // for some reason, this does a CASE SENSITIVE search which is NOT what I want. tables = tables.Where(tbl => tbl.Title.Contains("StringWithAnyCase"); return View(tables); The column is defiend as an nvarchar(50) in SQL Server 2008. Any help or guidance is greatly appreciated!

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  • Saving multiple items per single database cell...

    - by eugeneK
    Hi, i have a countries list. Each user can check multiple countries. Once saved, this "user country list" will be used to get whether other users fit into countries certain user chose. Question is what would be the most efficient approach to this problem... I have one, one to save user selection as delimited list like Canada,USA,France ... in single varchar(max) field but problem with it would be that once user from Germany enters page i perform this check on. To search for Germany i would be needed to get all items and un-delimit each field to check against value or to use sql 'like' which again is pretty damn slow.. If you have better solution or some tips i would be glad to hear. Just to make sure, many users will have their own selections of countries from which and only they want to have users to land on their page. While millions of users will reach those pages. So the faster approach will be the better. technology, MSSQL and ASP.NET thanks

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  • Windows Azure Table Storage Error when in the cloud

    - by Dan Jones
    hey, I downloaded the simple table storage sample on Cloudy in Seattle blog It works perfect when aimed at local storage but when I change to point to azure storage i get the following error Screenshot (on skydrive) http://cid-00341536d0f91b53.skydrive.live.com/self.aspx/.Public/error.png anyone see this before? thanks guys

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  • Returning data from SQL Server reporting web service call

    - by user79339
    Hi, I am generating a report that contains the version number. The version number is stored in the DB and retrieved/incremented as part of the report generation. The only problem is, I am calling SSRS via a web service call, which returns the generated report as a byte array. Is there any way to get the version number out of this generated report? For example to display a dialog that says "You generated Status Report, Version number 3". I tried passing in an output parameter and setting it inside the storedproc. Its modified when i execute it in sql management studio, but not in the reporting studio. Or atleast i can't seem to bind to the modified, post execution value (using expression "=Parameters!ReportVersion.Value"). Of course, I could get/increment the version number from database myself before calling the SSRS webservice and pass it along as a parameter to the Report, but that might cause concurrancy problems. On the whole, it just seems neater for the storedproc to access/generate a version number and return it to the ReportingEngine, which will generate the report with the version number and return the updated version number to the WebService client. Any thoughts/Ideas?

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  • SQL Server CE rollback does not undo delete.

    - by INTPnerd
    I am using SQL Server CE 3.5 and C# with the .NET Compact Framework 3.5. In my code I am inserting a row, then starting a transaction, then deleting that row from a table, and then doing a rollback on that transaction. But this does not undo the deletion. Why not? Here is my code: SqlCeConnection conn = ConnectionSingleton.Instance; conn.Open(); UsersTable table = new UsersTable(); table.DeleteAll(); MessageBox.Show("user count in beginning after delete: " + table.CountAll()); table.Insert( new User(){Id = 0, IsManager = true, Pwd = "1234", Username = "Me"}); MessageBox.Show("user count after insert: " + table.CountAll()); SqlCeTransaction transaction = conn.BeginTransaction(); table.DeleteAll(); transaction.Rollback(); transaction.Dispose(); MessageBox.Show("user count after rollback delete all: " + table.CountAll()); The messages indicate that everything works as expected until the very end where the table has a count of 0 indicating the rollback did not undo the deletion.

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  • New Marketing Assets Available

    - by swalker
    NEW translated demand generation materials available for the following Oracle Marketing Kits, designed to help partners generate sales around Oracle's solutions: Server & Storage: Improve Database Capacity Management with Oracle Storage and Hybrid Columnar Compression Server & Storage: Accelerating Database Test & Development with Sun ZFS Storage Appliance Server & Storage: Upgrade SAN Storage to Oracle Pillar Axiom Server & Storage: SPARC Refresh with Oracle Solaris Operating System Server & Storage: SPARC Server Refresh: The Next Level of Datacenter Performance with Oracle’s New SPARC Servers Server & Storage: Oracle Server Virtualization Server & Storage: Oracle Desktop Virtualization

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  • Online graphing and data visualization frameworks

    - by Marques
    I have been looking around at web applications and websites with rich graphs, charts, and data visualization and for the most part have been able to determine which frameworks or tools websites are using. However I was looking over 'resumup.com' and couldn't determine what they are using. Does anyone know off hand or can you tell? It doesn't seem like any javascript framework i've seen unless its custom...is it some sort of flash or flex framework? Any help would be greatly appreciated. Thanks, Marques

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  • (mySQL) Unable to query 2 tables properly for data

    - by Devner
    I have 2 tables. One is 'page_links' and the other is 'rpp'. Table page_links is the superset of table rpp. The following is the schema of my tables: -- Table structure for table `page_links` -- CREATE TABLE IF NOT EXISTS `page_links` ( `page` varchar(255) NOT NULL, `page_link` varchar(100) NOT NULL, `heading_id` tinyint(3) unsigned NOT NULL, PRIMARY KEY (`page`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -- Dumping data for table `page_links` -- INSERT INTO `page_links` (`page`, `page_link`, `heading_id`) VALUES ('a1.php', 'A1', 8), ('b1.php', 'B1', 8), ('c1.php', 'C1', 5), ('d1.php', 'D1', 5), ('e1.php', 'E1', 8), ('f1.php', 'F1', 8), ('g1.php', 'G1', 8), ('h1.php', 'H1', 1), ('i1.php', 'I1', 1), ('j1.php', 'J1', 8), ('k1.php', 'K1', 8), ('l1.php', 'L1', 8), ('m1.php', 'M1', 8), ('n1.php', 'N1', 8), ('o1.php', 'O1', 8), ('p1.php', 'P1', 4), ('q1.php', 'Q1', 5), ('r1.php', 'R1', 4); -- Table structure for table `rpp` -- CREATE TABLE IF NOT EXISTS `rpp` ( `role_id` tinyint(3) unsigned NOT NULL, `page` varchar(255) NOT NULL, `is_allowed` tinyint(1) NOT NULL, PRIMARY KEY (`role_id`,`page`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -- Dumping data for table `rpp` -- INSERT INTO `rpp` (`role_id`, `page`, `is_allowed`) VALUES (3, 'a1.php', 1), (3, 'b1.php', 1), (3, 'c1.php', 1), (3, 'd1.php', 1), (3, 'e1.php', 1), (3, 'f1.php', 1), (3, 'h1.php', 1), (3, 'i1.php', 1), (3, 'l1.php', 1), (3, 'm1.php', 1), (3, 'n1.php', 1), (4, 'a1.php', 1), (4, 'b1.php', 1), (4, 'q1.php', 1), (5, 'r1.php', 1); WHAT I AM TRYING TO DO: I am trying to query both the above tables (in a single query) in such a way that all the pages from page_links are displayed along with the is_allowed value from rpp for a particular role. For example, I want to get the is_allowed value of all the pages from rpp for role_id = 3 and at the same time, list all the available pages from page_links. A clear example of my expected result would be: page is_allowed role_id ---------------------------------------- a1.php 1 3 b1.php 1 3 c1.php 1 3 d1.php 1 3 e1.php 1 3 f1.php 1 3 g1.php NULL NULL h1.php 1 3 i1.php 1 3 j1.php NULL NULL k1.php NULL NULL l1.php 1 3 m1.php 1 3 n1.php 1 3 o1.php NULL NULL p1.php NULL NULL q1.php NULL NULL r1.php NULL NULL One more example of my desired result could be achieved by doing a LEFT JOIN rpp ON page_links.page = rpp.page but we need to omit using role_id = 3 (or any value) to be able to get that. But I do want to specify the role_id as well and get the results. I need the query to be able to get this result. I would appreciate any replies that could help me with this. If you can suggest me any changes as well to the table(s) design to be able to achieve the desired result, that's good as well. Thanks in advance.

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  • Which fieldtype is best for storing PRICE values?

    - by BerggreenDK
    Hi there I am wondering whats the best "price field" in MSSQL for a shoplike structure? Looking at this overview: http://www.teratrax.com/sql_guide/data_types/sql_server_data_types.html We have datatypes called money, smallmoney, then we have decimal/numeric and lastly float and real Name, memory/disk-usage and value ranges: Money: 8 bytes (values: -922,337,203,685,477.5808 to +922,337,203,685,477.5807) Smallmoney: 4 bytes (values: -214,748.3648 to +214,748.3647) Decimal: 9 [default, min. 5] bytes (values: -10^38 +1 to 10^38 -1 ) Float: 8 bytes (values: -1.79E+308 to 1.79E+308 ) Real: 4 bytes (values: -3.40E+38 to 3.40E+38 ) My question is: is it really wise to store pricevalues in those types? what about eg. INT? Int: 4 bytes (values: -2,147,483,648 to 2,147,483,647) Lets say a shop uses dollars, they have cents, but I dont see prices being $49.2142342 so the use of a lot of decimals showing cents seems waste of SQL bandwidth. Secondly, most shops wouldn't show any prices near 200.000.000 (not in normal webshops at least... unless someone is trying to sell me a famous tower in Paris) So why not go for an int? An int is fast, its only 4 bytes and you can easily make decimals, by saving values in cents instead of dollars and then divide when you present the values. The other approach would be to use smallmoney which is 4 bytes too, but this will require the math part of the CPU to do the calc, where as Int is integer power... on the downside you will need to divide every single outcome. Are there any "currency" related problems with regionalsettings when using smallmoney/money fields? what will these transfer too in C#/.NET ? Any pros/cons? Go for integer prices or smallmoney or some other? Whats does your experience tell?

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  • MVC4 Model in View has nested data - cannot get data in model

    - by Taersious
    I have a Model defined that gets me a View with a list of RadioButtons, per IEnumerable. Within that Model, I want to display a list of checkboxes that will vary based on the item selected. Finally, there will be a Textarea in the same view once the user has selected from the available checkboxes, with some dynamic text there based on the CheckBoxes that are selected. What we should end up with is a Table-per-hierarchy. The layout is such that the RadioButtonList is in the first table cell, the CheckBoxList is in the middle table cell, and the Textarea is ini the right table cell. If anyone can guide me to what my model-view should be to achieve this result, I'll be most pleased... Here are my codes: // // View Model for implementing radio button list public class RadioButtonViewModel { // objects public List<RadioButtonItem> RadioButtonList { get; set; } public string SelectedRadioButton { get; set; } } // // Object for handling each radio button public class RadioButtonItem { // this object public string Name { get; set; } public bool Selected { get; set; } public int ObjectId { get; set; } // columns public virtual IEnumerable<CheckBoxItem> CheckBoxItems { get; set; } } // // Object for handling each checkbox public class CheckBoxViewModel { public List<CheckBoxItem> CheckBoxList { get; set; } } // // Object for handling each check box public class CheckBoxItem { public string Name { get; set; } public bool Selected { get; set; } public int ObjectId { get; set; } public virtual RadioButtonItem RadioButtonItem { get; set; } } and the view @model IEnumerable<EF_Utility.Models.RadioButtonItem> @{ ViewBag.Title = "Connect"; ViewBag.Selected = Request["name"] != null ? Request["name"].ToString() : ""; } @using (Html.BeginForm("Objects" , "Home", FormMethod.Post) ){ @Html.ValidationSummary(true) <table> <tbody> <tr> <td style="border: 1px solid grey; vertical-align:top;"> <table> <tbody> <tr> <th style="text-align:left; width: 50px;">Select</th> <th style="text-align:left;">View or Table Name</th> </tr> @{ foreach (EF_Utility.Models.RadioButtonItem item in @Model ) { <tr> <td> @Html.RadioButton("RadioButtonViewModel.SelectedRadioButton", item.Name, ViewBag.Selected == item.Name ? true : item.Selected, new { @onclick = "this.form.action='/Home/Connect?name=" + item.Name + "'; this.form.submit(); " }) </td> <td> @Html.DisplayFor(i => item.Name) </td> </tr> } } </tbody> </table> </td> <td style="border: 1px solid grey; width: 220px; vertical-align:top; @(ViewBag.Selected == "" ? "display:none;" : "")"> <table> <tbody> <tr> <th>Column </th> </tr> <tr> <td><!-- checkboxes will go here --> </td> </tr> </tbody> </table> </td> <td style="border: 1px solid grey; vertical-align:top; @(ViewBag.Selected == "" ? "display:none;" : "")"> <textarea name="output" id="output" rows="24" cols="48"></textarea> </td> </tr> </tbody> </table> } and the relevant controller public ActionResult Connect() { /* TEST SESSION FIRST*/ if( Session["connstr"] == null) return RedirectToAction("Index"); else { ViewBag.Message = ""; ViewBag.ConnectionString = Server.UrlDecode( Session["connstr"].ToString() ); ViewBag.Server = ParseConnectionString( ViewBag.ConnectionString, "Data Source" ); ViewBag.Database = ParseConnectionString( ViewBag.ConnectionString, "Initial Catalog" ); using( var db = new SysDbContext(ViewBag.ConnectionString)) { var objects = db.Set<SqlObject>().ToArray(); var model = objects .Select( o => new RadioButtonItem { Name = o.Name, Selected = false, ObjectId = o.Object_Id, CheckBoxItems = Enumerable.Empty<EF_Utility.Models.CheckBoxItem>() } ) .OrderBy( rb => rb.Name ); return View( model ); } } } What I am missing it seems, is the code in my Connect() method that will bring the data context forward; at that point, it should be fairly straight-forward to set up the Html for the View. EDIT ** So I am going to need to bind the RadioButtonItem to the view with something like the following, except my CheckBoxList will NOT be an empty set. // // POST: /Home/Connect/ [HttpPost] public ActionResult Connect( RadioButtonItem rbl ) { /* TEST SESSION FIRST*/ if ( Session["connstr"] == null ) return RedirectToAction( "Index" ); else { ViewBag.Message = ""; ViewBag.ConnectionString = Server.UrlDecode( Session["connstr"].ToString() ); ViewBag.Server = ParseConnectionString( ViewBag.ConnectionString, "Data Source" ); ViewBag.Database = ParseConnectionString( ViewBag.ConnectionString, "Initial Catalog" ); using ( var db = new SysDbContext( ViewBag.ConnectionString ) ) { var objects = db.Set<SqlObject>().ToArray(); var model = objects .Select( o => new RadioButtonItem { Name = o.Name, Selected = false, ObjectId = o.Object_Id, CheckBoxItems = Enumerable.Empty<EF_Utility.Models.CheckBoxItem>() } ) .OrderBy( rb => rb.Name ); return View( model ); } } }

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  • Java Data Structure

    - by Joe
    Hi there, I'm looking for a data structure that will act like a Queue so that I can hava First In First Out behaviour, but ideally I would also be able to see if an element exists in that Queue in constant time as you can do with a HashMap, rather than the linear time that you get with a LinkedList. I thought a LinkedHashMap might do the job, but although I could make an iterator and just take and then remove the first element of the iteration to produce a sort of poll() method, I'm wondering if there is a better way. Many thanks in advance

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  • SQL indexes for "not equal" searches

    - by bortzmeyer
    The SQL index allows to find quickly a string which matches my query. Now, I have to search in a big table the strings which do not match. Of course, the normal index does not help and I have to do a slow sequential scan: essais=> \d phone_idx Index "public.phone_idx" Column | Type --------+------ phone | text btree, for table "public.phonespersons" essais=> EXPLAIN SELECT person FROM PhonesPersons WHERE phone = '+33 1234567'; QUERY PLAN ------------------------------------------------------------------------------- Index Scan using phone_idx on phonespersons (cost=0.00..8.41 rows=1 width=4) Index Cond: (phone = '+33 1234567'::text) (2 rows) essais=> EXPLAIN SELECT person FROM PhonesPersons WHERE phone != '+33 1234567'; QUERY PLAN ---------------------------------------------------------------------- Seq Scan on phonespersons (cost=0.00..18621.00 rows=999999 width=4) Filter: (phone <> '+33 1234567'::text) (2 rows) I understand (see Mark Byers' very good explanations) that PostgreSQL can decide not to use an index when it sees that a sequential scan would be faster (for instance if almost all the tuples match). But, here, "not equal" searches are really slower. Any way to make these "is not equal to" searches faster? Here is another example, to address Mark Byers' excellent remarks. The index is used for the '=' query (which returns the vast majority of tuples) but not for the '!=' query: essais=> EXPLAIN ANALYZE SELECT person FROM EmailsPersons WHERE tld(email) = 'fr'; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------ Index Scan using tld_idx on emailspersons (cost=0.25..4010.79 rows=97033 width=4) (actual time=0.137..261.123 rows=97110 loops=1) Index Cond: (tld(email) = 'fr'::text) Total runtime: 444.800 ms (3 rows) essais=> EXPLAIN ANALYZE SELECT person FROM EmailsPersons WHERE tld(email) != 'fr'; QUERY PLAN -------------------------------------------------------------------------------------------------------------------- Seq Scan on emailspersons (cost=0.00..27129.00 rows=2967 width=4) (actual time=1.004..1031.224 rows=2890 loops=1) Filter: (tld(email) <> 'fr'::text) Total runtime: 1037.278 ms (3 rows) DBMS is PostgreSQL 8.3 (but I can upgrade to 8.4).

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  • Securing Coredata objects

    - by Abraham Durairaj
    I am working on an application which has got some sensitive information. I am aware that it would be difficult for a layman to hack into iphone to get the information. If I use SQLite directly I have something called SQLite Cipher to encrypt / encode the database. Is there anyway where I can have the same way of encrypting the coredata so it makes it hard for hackers to get into the data. Can someone shed some light on this? Thanks in Advance

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  • Combining two-part SQL query into one query

    - by user332523
    Hello, I have a SQL query that I'm currently solving by doing two queries. I am wondering if there is a way to do it in a single query that makes it more efficient. Consider two tables: Transaction_Entries table and Transactions, each one defined below: Transactions - id - reference_number (varchar) Transaction_Entries - id - account_id - transaction_id (references Transactions table) Notes: There are multiple transaction entries per transaction. Some transactions are related, and will have the same reference_number string. To get all transaction entries for Account X, then I would do SELECT E.*, T.reference_number FROM Transaction_Entries E JOIN Transactions T ON (E.transaction_id=T.id) where E.account_id = X The next part is the hard part. I want to find all related transactions, regardless of the account id. First I make a list of all the unique reference numbers I found in the previous result set. Then for each one, I can query all the transactions that have that reference number. Assume that I hold all the rows from the previous query in PreviousResultSet UniqueReferenceNumbers = GetUniqueReferenceNumbers(PreviousResultSet) // in Java foreach R in UniqueReferenceNumbers // in Java SELECT * FROM Transaction_Entries where transaction_id IN (SELECT * FROM Transactions WHERE reference_number=R Any suggestions how I can put this into a single efficient query?

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