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  • What are the types and inner workings of a query optimizer?

    - by Frank Developer
    As I understand it, most query optimizers are cost-based. Some can be influenced by hints like FIRST_ROWS(). Others are tailored for OLAP. Is it possible to know more detailed logic about how Informix IDS and SE's optimizers decide what's the best route for processing a query, other than SET EXPLAIN? Is there any documentation which illustrates the ranking of SELECT statements? I would imagine that "SELECT col FROM table WHERE ROWID = n" ranks 1st. What are the rest of them?.. If I'm not mistaking, Informix's ROWID is a SERIAL(INT) which allows for a max. of 2GB nrows, or maybe it uses INT9 for TB's nrows?.. However, I think Oracle uses HEX values for ROWID. Too bad ROWID can't be oftenly used, since a rows ROWID can change. So maybe ROWID is used by the optimizer as a counter? Perhaps, it could be used for implementing the query progress idea I mentioned in my "Begin viewing query results before query completes" question? For some reason, I feel it wouldn't be that difficult to report a query's progress while being processed, perhaps at the expense of some slight overhead, but it would be nice to know ahead of time: A "Google-like" estimate of how many rows meet a query's criteria, display it's progress every 100, 200, 500 or 1,000 rows, give users the ability to cancel it at anytime and start displaying the qualifying rows as they are being put into the current list, while it continues searching?.. This is just one example, perhaps we could think other neat/useful features, the ingridients are more or less there. Perhaps we could fine-tune each query with more granularity than currently available? OLTP queries tend to be mostly static and pre-defined. The "what-if's" are more OLAP, so let's try to add more control and intelligence to it? So, therefore, being able to more precisely control, not "hint-influence" a query is what's needed and therefore it would be necessary to know how the optimizers logic is programmed. We can then have Dynamic SELECT and other statements for specific situations! Maybe even tell IDS to read blocks of indexes nodes at-a-time instead of one-by-one, etc. etc.

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  • How to add if statement in SQL ?

    - by shin
    I have a following MySQL with two parameters, $catname and $limit=1. And it is working fine. SELECT P.*, C.Name AS CatName FROM omc_product AS P LEFT JOIN omc_category AS C ON C.id = P.category_id WHERE C.Name = '$catname' AND p.status = 'active' ORDER BY RAND() LIMIT 0, $limit Now I want to add another parameter $order. $order can be either ODER BY RAND() or ORDER BY product_order in the table omc_product. Could anyone tell me how to write this query please? Thanks in advance.

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  • TSQL: finding unique entries in a single table

    - by pcampbell
    Consider a table or CTE structured like this: Name Num ---- ---- Abc 12 Abc 12 XYZ 70 XYZ 80 Bar 50 Bar 55 Foo 44 Foo 44 Baz 88 The requirement is to determine the Name where multiple different Nums exist. The desired resultset is Name ---- XYZ Bar What TSQL statement would you use to derive this resultset?

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  • How to make an entity out of a join table without primary key

    - by tputkonen
    I'm trying to generate JPA entities out of an existing database having an "interesting" design. Database has a table called UserSet, which can have links to several other UserSets. There is a one to many relation between UserSets and LinkedUserSets. LinkedUserSets also has one to one relation to UserSets. I tried to generate a JPA Entity out of the database structure using Dali JPA Tools. The resulting entity Linkeduserset misses @Id or @EmbeddedId annotation and thus failes to compile. As the resulting entity contains only two @JoinColumns (which cannot be marked as @Id), I have not so far found a way around this issue. Database structure can not be modified in any way. Is there a way to overcome this somehow? Relevant pars of create table statements: CREATE TABLE `LinkedUserSets` ( `UsrSetID` INT(11) NOT NULL DEFAULT '0' , `ChildID` INT(11) NOT NULL DEFAULT '0' , CONSTRAINT `fk_LinkedUserSets_UserSet1` FOREIGN KEY (`UsrSetID` ) REFERENCES `UserSet` (`UsrSetID` )); CREATE TABLE `UserSet` ( `UsrSetID` INT(11) NOT NULL AUTO_INCREMENT , PRIMARY KEY (`UsrSetID`), CONSTRAINT `fk_UserSet_LinkedUserSets1` FOREIGN KEY (`UsrSetID` ) REFERENCES `LinkedUserSets` (`ChildID` )); Generated entities: @Entity @Table(name="linkedusersets") public class Linkeduserset { //bi-directional many-to-one association to Userset @ManyToOne @JoinColumn(name="UsrSetID") private Userset userset1; //bi-directional one-to-one association to Userset @OneToOne @JoinColumn(name="ChildID") private Userset userset2; } @Entity @Table(name="userset") public class Userset { private static final long serialVersionUID = 1L; @Id @Column(name="UsrSetID") private int jngSetID; //bi-directional many-to-one association to Linkeduserset @OneToMany(mappedBy="userset1") private Set<Linkeduserset> linkedusersets; //bi-directional one-to-one association to Linkeduserset @OneToOne(mappedBy="userset2") private Linkeduserset linkeduserset; } Error message: Entity "Linkeduserset" has no Id or EmbeddedId

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  • Conversion failed: SqlParameter and DateTime

    - by Tim
    I'm changing old,vulnerable sqlcommands with SqlParameters but get a SqlException: System.Data.SqlClient.SqlException {"Conversion failed when converting datetime from character string."} on sqlCommand.ExecuteScalar() Dim sqlString As String = _ "SELECT TOP 1 " & _ "fiSL " & _ "FROM " & _ "tabData AS D " & _ "WHERE " & _ "D.SSN_Number = '@SSN_Number' " & _ "AND D.fiProductType = 1 " & _ "AND D.Repair_Completion_Date > '@Repair_Completion_Date' " & _ "ORDER BY " & _ "D.Repair_Completion_Date ASC" Dim obj As Object Dim sqlCommand As SqlCommand Try sqlCommand = New SqlCommand(sqlString, Common.MyDB.SqlConn_RM2) sqlCommand.CommandTimeout = 120 sqlCommand.Parameters.AddWithValue("@SSN_Number", myClaim.SSNNumber) sqlCommand.Parameters.AddWithValue("@Repair_Completion_Date", myClaim.RepairCompletionDate) If Common.MyDB.SqlConn_RM2.State <> System.Data.ConnectionState.Open Then Common.MyDB.SqlConn_RM2.Open() obj = sqlCommand.ExecuteScalar() Catch ex As Exception Dim debug As String = ex.ToString Finally Common.MyDB.SqlConn_RM2.Close() End Try myClaim.RepairCompletionDate is a SQLDateTime. Do i have to remove the quotes in the sqlString to compare Date columns? But then i dont get a exception but incorrect results.

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  • Replacing characters with specified one

    - by mahesh
    Hello All, I have a string as follows - MFMFMF now i want to change this string to FMFMFM how to do this , help needed pls i had tried select replace(replace('mfmfmf','M','F'),'F','M') this gives me result - MMMMMM which i donot what i want the output to be FMFMFM Need your help D.Mahesh

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  • C# : DBConnection.Open() timeout is too long.

    - by leo
    Hi, I'm trying to connect to a server that the user inputs. When the server doesn't exist, I'd like to give a quick feedback to the end-user so he can correct what he's typed. Is there any way to test if a server exists before trying to connect ? Thanks

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  • An INSERT conditioned on COUNT

    - by Anders Feder
    How can I construct a MySQL INSERT query that only executes if the number of rows satisfying some condition already in the table is less than 20, and fails otherwise? That is, if the table has 18 rows satisfying the condition, then the INSERT should proceed. If the table has 23 rows satisfying the condition, then the INSERT should fail. For atomicity, I need to express this in a single query, so two requests can not INSERT at the same time, each in the 'belief' that only 19 rows satisfy the condition. Thank you.

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  • SQL Concurrent test update question

    - by ptoinson
    Howdy Folks, I have a SQLServer 2008 database in which I have a table for Tags. A tag is just an id and a name. The definition of the tags table looks like: CREATE TABLE [dbo].[Tag]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](255) NOT NULL CONSTRAINT [PK_Tag] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ) Name is also a unique index. further I have several processes adding data to this table at a pretty rapid rate. These processes use a stored proc that looks like: ALTER PROC [dbo].[lg_Tag_Insert] @Name varchar(255) AS DECLARE @ID int SET @ID = (select ID from Tag where Name=@Name ) if @ID is null begin INSERT Tag(Name) VALUES (@Name) RETURN SCOPE_IDENTITY() end else begin return @ID end My issues is that, other than being a novice at concurrent database design, there seems to be a race condition that is causing me to occasionally get an error that I'm trying to enter duplicate keys (Name) into the DB. The error is: Cannot insert duplicate key row in object 'dbo.Tag' with unique index 'IX_Tag_Name'. This makes sense, I'm just not sure how to fix this. If it where code I would know how to lock the right areas. SQLServer is quite a different beast. First question is what is the proper way to code this 'check, then update pattern'? It seems I need to get an exclusive lock on the row during the check, rather than a shared lock, but it's not clear to me the best way to do that. Any help in the right direction will be greatly appreciated. Thanks in advance.

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  • why this left join query failed to load all the data in left table ?

    - by lzyy
    users table +-----+-----------+ | id | username | +-----+-----------+ | 1 | tom | | 2 | jelly | | 3 | foo | | 4 | bar | +-----+-----------+ groups table +----+---------+-----------------------------+ | id | user_id | title | +----+---------+-----------------------------+ | 2 | 1 | title 1 | | 4 | 1 | title 2 | +----+---------+-----------------------------+ the query SELECT users.username,users.id,count(groups.title) as group_count FROM users LEFT JOIN groups ON users.id = groups.user_id result +----------+----+-------------+ | username | id | group_count | +----------+----+-------------+ | tom | 1 | 2 | +----------+----+-------------+ where is the rest users' info? the result is the same as inner join , shouldn't left join return all left table's data? PS:I'm using mysql

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  • NHibernate - does it work well with database-level cascading deletions on foreign key constraints

    - by Nelson LaQuet
    Dose nHibernate play well with database level cascading deletions? What I mean is that if I have a constraint set at the RDBMS level to cascade delete all orphans, will nHibernate invoke any custom delete logic at the application level if I were to delete an entity though nHibernate? Or should I remove the cascading deletions from the RDBMS level and just use the cascading delete feature of nHibernate itself by defining that behavior though its configuration? Thanks

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  • Violation of PRIMARY KEY constraint 'PK_

    - by abhi
    hi am trying to write a code in which i need to perform a update but on primary keys how do i achieve it i have written the following code: kindly look at it let me know where m wrong Protected Sub rgKMSLoc_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles rgKMSLoc.UpdateCommand Try KAYAReqConn.Open() If TypeOf e.Item Is GridEditableItem Then Dim strItemID As String = CType(e.Item.FindControl("hdnID"), HiddenField).Value Dim strrcmbLocation As String = CType(e.Item.FindControl("rcmbLocation"), RadComboBox).SelectedValue Dim strKubeLocation As String = CType(e.Item.FindControl("txtKubeLocation"), TextBox).Text Dim strCSVCode As String = CType(e.Item.FindControl("txtCSVCode"), TextBox).Text SQLCmd = New SqlCommand("SELECT * FROM MstKMSLocKubeLocMapping WHERE LocationID= '" & rcmbLocation.SelectedValue & "'", KAYAReqConn) Dim dr As SqlDataReader dr = SQLCmd.ExecuteReader If dr.HasRows Then lblMsgWarning.Text = "<font color=red>""User ID Already Exists" Exit Sub End If dr.Close() SQLCmd = New SqlCommand("UPDATE MstKMSLocKubeLocMapping SET LocationID=@Location,KubeLocation=@KubeLocation,CSVCode=@CSVCode WHERE LocationID = '" & strItemID & "'", KAYAReqConn) SQLCmd.Parameters.AddWithValue("@Location", Replace(strrcmbLocation, "'", "''")) SQLCmd.Parameters.AddWithValue("@KubeLocation", Replace(strKubeLocation, "'", "''")) SQLCmd.Parameters.AddWithValue("@CSVCode", Replace(strCSVCode, "'", "''")) SQLCmd.Parameters.AddWithValue("@Status", "A") SQLCmd.ExecuteNonQuery() lblMessageUpdate.Text = "<font color=blue>""Record Updated SuccessFully" SQLCmd.Dispose() rgKMSLoc.Rebind() End If Catch ex As Exception Response.Write(ex.ToString) Finally KAYAReqConn.Close() End Try End Sub this is my designer page' Location: ' / ' DataSourceID="dsrcmbLocation" DataTextField="Location" DataValueField="LocationID" Height="150px" Kube Location: ' Class="forTextBox" MaxLength="4" onkeypress="return filterInput(2,event);" CSV Code: ' Class="forTextBox" MaxLength="4" onkeypress="return filterInput(2,event);" <tr class="tableRow"> <td colspan="2" align="center" class="tableCell"> <asp:ImageButton ID="btnUpdate" runat="server" CommandName="Update" CausesValidation="true" ValidationGroup="Update" ImageUrl="~/Images/update.gif"></asp:ImageButton> <asp:ImageButton ID="btnCancel" runat="server" CausesValidation="false" CommandName="Cancel" ImageUrl="~/Images/No.gif"></asp:ImageButton> </td> </tr> </table> </FormTemplate> </EditFormSettings> Locationid is my primary key

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  • DataContext Refresh and PropertyChanging & PropertyChanged Events

    - by Scott
    I'm in a situation where I am being informed from an outside source that a particular entity has been altered outside my current datacontext. I'm able to find the entity and call refresh like so MyDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myEntity); and the properties which have been altered on the entity are updated correctly. However neither of the INotifyPropertyChanging INotifyPropertyChanged appear to be raised when the refresh occurs and this leaves my UI displaying incorrect information. I'm aware that Refresh() fails to use the correct property getters and setters on the entity to raise the change notification events, but perhaps there is another way to accomplish the same thing? Am I doing something wrong? Is there a better method than Refresh? If Refresh is the only option, does anyone have a work around?

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  • Creating a Rails query from a hash of user input

    - by Jamie
    I'm attempting to create a fairly complex search engine for a project using a variable number of search criteria. The user input is sorted into an array of hashes. The hashes contain the following information: { :column => "", :value => "", :operator => "", # Such as: =, !=, <, >, etc. :and_or => "", # Two possible values: "and" and "or" } How can I loop through this array and use the information in these hashes to make an ActiveRecord WHERE query?

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  • How To Find Reasons of Why Site Goes Online/Offline

    - by HollerTrain
    Seems today a website I manage has been going online and offline throughout the entire day. I have no idea what is causing the issue so I am seeking guidance on where to start. It is a Wordpress based site. So here is what I DO know: I use a program that pings the server every minute and when the server is not responding me it emails me, so I can know exactly when the site is online and offline. The site between 8pm to 12pm 12.28, and around the 1a hour early morning 12.29 (New York City timezone, and all times below are in same timezone). At the time of the ups/downs I see a lot of strain on the memory usage. Look at the load average when the site is going online/offline (http://screencast.com/t/BRlfXkqrbJII). Then I ran this command to restart http (http://screencast.com/t/usVtYWZ2Qi) and the memory usage then goes down to this (http://screencast.com/t/VdTIy3bgZiQB). An hour after I restarted http, the site then went offline/online so restarting the http didn't do much help. When the site is going offline/online, I ran the top command and get this (http://screencast.com/t/zEwr7YQj3). Here is a top command when the site is at it's lowest (http://screencast.com/t/eaMfha9lbT - so this would be dubbged "normal"). Here is a bandwidth report (http://screencast.com/t/AS0h2CH1Gypq). The traffic doesn't seem to be that much (http://screencast.com/t/s7hrWNNic1K), but looking at my times the site is going up/down this may be one of the reasons? I have the dvp Nitro package at Media Temple (http://mediatemple.net/webhosting/nitro/). So at this point I would request some help in trying to figure out what the cause of this is, and how I can go about pinpointing this issue. ANY HELP is greatly appreciated.

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  • PostgreSQL: SELECT all fields, filter some

    - by Adam Matan
    Hi, In one of our databases, there is a table with dozens of columns, one of which is a geometry column. I want to SELECT rows from the table, with the geometry transformed to another SRID. I want to use something like: `SELECT *` in order to avoid: SELECT col_a, col_b, col_c, col_d, col_e, col_f, col_g, col_h, transform(the_geom, NEW_SRID), ..., col_z Any ideas? Adam

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  • Fast way to code forms in C# which is bind to SQL data

    - by adopilot
    I am coming from MS-ACESS world and their programing habits, There was nice utility to make form from table, You can simply hit right click on table and make form for it. Now I looking for something similar for Visual Studio and WinForms. I am trying to develop simple application for which I need to have more then 30 forms for handling data, till now I designed database tables, keys and sprocs in SQL2008 and before I start coding forms for handling data, I asking You for main guidelines how to save my time while coding forms.

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  • Error invoking stored procedure with input parameter from ADO.Net

    - by George2
    Hello everyone, I am using VSTS 2008 + C# + .Net 3.5 + ADO.Net. Here is my code and related error message. The error message says, @Param1 is not supplied, but actually it is supplied in my code. Any ideas what is wrong? System.Data.SqlClient.SqlException: Procedure or function 'Pr_Foo' expects parameter '@Param1', which was not supplied. class Program { private static SqlCommand _command; private static SqlConnection connection; private static readonly string _storedProcedureName = "Pr_Foo"; private static readonly string connectionString = "server=.;integrated Security=sspi;initial catalog=FooDB"; public static void Prepare() { connection = new SqlConnection(connectionString); connection.Open(); _command = connection.CreateCommand(); _command.CommandText = _storedProcedureName; _command.CommandType = CommandType.StoredProcedure; } public static void Dispose() { connection.Close(); } public static void Run() { try { SqlParameter Param1 = _command.Parameters.Add("@Param1", SqlDbType.Int, 300101); Param1.Direction = ParameterDirection.Input; SqlParameter Param2 = _command.Parameters.Add("@Param2", SqlDbType.Int, 100); portal_SiteInfoID.Direction = ParameterDirection.Input; SqlParameter Param3 = _command.Parameters.Add("@Param3", SqlDbType.Int, 200); portal_RoleInfoID.Direction = ParameterDirection.Input; _command.ExecuteScalar(); } catch (Exception e) { Console.WriteLine(e); } } static void Main(string[] args) { try { Prepare(); Thread t1 = new Thread(Program.Run); t1.Start(); t1.Join(); Dispose(); } catch (Exception ex) { Console.WriteLine(ex.Message + "\t" + ex.StackTrace); } } } Thanks in advance, George

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  • automatic id generation which is a primary key

    - by abhi
    in vb.net while entering a new entry i want to assign a record a unique id like in case of numeric i do this way Dim ItemID As Integer KAYAReqConn.Open() SQLCmd = New SqlCommand("SELECT ISNULL(MAX(ItemID),0) AS ItemID from MstItem", ReqConn) Dim dr As SqlDataReader dr = SQLCmd.ExecuteReader If dr.HasRows Then dr.Read() ItemID = dr("ItemID") + 1 End If dr.Close() in this case m using itemid as a unique id and the format is 1,2,3... and m finding out the max and assigning to a new record but how to assign if the previous id is of the a00001,a00002,a00003,a00004...so on. how i do i produce a unique id in this case

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  • how to use insert command in sql analysis services

    - by imcolin
    Hi all, I have a problem regarding how to use insert command in ssas, i try to send a request to server, server give a response saying "No binding exists for it", my request envelope is:- <Envelope xmlns="http://schemas.xmlsoap.org/soap/envelope/"> SSAS SsasCubes Sales Territory Sales Territory Key fds aa 1033 Should i create a attribut binding before using insert command??? any body can help me ? one more question, when i use Update command in ssas, I also got a error say "Attributes cannot appear in Where ". can you tell me why?? Thanks

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  • C# SqlDataAdapter not populating DataSet

    - by Wesley
    I have searched the net and searched the net only to not quite find the probably I am running into. I am currently having an issue getting a SqlDataAdapter to populate a DataSet. I am running Visual Studio 2008 and the query is being sent to a local instance of SqlServer 2008. If I run the query itself in SqlServer, I do get information. Code is as follows: string theQuery = "select Password from Employees where employee_ID = '@EmplID'"; SqlDataAdapter theDataAdapter = new SqlDataAdapter(); theDataAdapter.SelectCommand = new SqlCommand(theQuery, conn); theDataAdapter.SelectCommand.Parameters.Add("@EmplID", SqlDbType.VarChar).Value = "EmployeeName"; theDataAdapter.Fill(theSet); The code to read the dataset: foreach (DataRow theRow in theSet.Tables[0].Rows) { //process row info } If there is any more info I can supply please let me know.

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