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  • MySQL: Limit rows linked to each joined row

    - by SolidSnakeGTI
    Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

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  • How efficient is a details table?

    - by Jeffrey Lott
    At my job, we have pseudo-standard of creating one table to hold the "standard" information for an entity, and a second table, named like 'TableNameDetails', which holds optional data elements. On average, for every row in the main table will have about 8-10 detail rows in it. My question is: What kind of performance impacts does this have over adding these details as additional nullable columns on the main table?

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  • MySQL - Where - search string - MATCH.

    - by Jamie
    Hi guys, Quick question. I'm in a bit of a rush but if someone could quickly point me in the right direction I would be very very happy. I have a field in the db, let's call it field_a which returns a string in the format "20,50,60,80" etc. I wish to do a query which will search in this field to see if 20 exists. Could I use MySQL MATCH or is there a better way? Thank you!

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  • How can I bind an Enum to a DbType of bit or int?

    - by uriDium
    Hi I am using Linq2Sql and want to bind an objects field (which is enum) to either a bit or a int type in the database. For example I want have a gender field in my model. I have already edited the DBML and changed the Type to point to my enum. I want to create Radio buttons (which I think I have figured out) for gender and dropdown lists for other areas using the same idea. My enum looks like this public enum Gender { Male, Female } Mapping between DbType 'int' and Type 'Project.Models.Gender' in Column 'Gender' of Type 'Candidate' is not supported. Any ideas on how to do this mapping. Am I missing something on the enums.

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  • Databinding in combo box

    - by muralekarthick
    Hi I have two forms, and a class, queries return in Stored procedure. Stored Procedure: ALTER PROCEDURE [dbo].[Payment_Join] @reference nvarchar(20) AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here SELECT p.iPaymentID,p.nvReference,pt.nvPaymentType,p.iAmount,m.nvMethod,u.nvUsers,p.tUpdateTime FROM Payment p, tblPaymentType pt, tblPaymentMethod m, tblUsers u WHERE p.nvReference = @reference and p.iPaymentTypeID = pt.iPaymentTypeID and p.iMethodID = m.iMethodID and p.iUsersID = u.iUsersID END payment.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using System.Data.SqlClient; using System.Windows.Forms; namespace Finance { class payment { string connection = global::Finance.Properties.Settings.Default.PaymentConnectionString; #region Fields int _paymentid = 0; string _reference = string.Empty; string _paymenttype; double _amount = 0; string _paymentmethod; string _employeename; DateTime _updatetime = DateTime.Now; #endregion #region Properties public int paymentid { get { return _paymentid; } set { _paymentid = value; } } public string reference { get { return _reference; } set { _reference = value; } } public string paymenttype { get { return _paymenttype; } set { _paymenttype = value; } } public string paymentmethod { get { return _paymentmethod; } set { _paymentmethod = value; } } public double amount { get { return _amount;} set { _amount = value; } } public string employeename { get { return _employeename; } set { _employeename = value; } } public DateTime updatetime { get { return _updatetime; } set { _updatetime = value; } } #endregion #region Constructor public payment() { } public payment(string refer) { reference = refer; } public payment(int paymentID, string Reference, string Paymenttype, double Amount, string Paymentmethod, string Employeename, DateTime Time) { paymentid = paymentID; reference = Reference; paymenttype = Paymenttype; amount = Amount; paymentmethod = Paymentmethod; employeename = Employeename; updatetime = Time; } #endregion #region Methods public void Save() { try { SqlConnection connect = new SqlConnection(connection); SqlCommand command = new SqlCommand("payment_create", connect); command.CommandType = CommandType.StoredProcedure; command.Parameters.Add(new SqlParameter("@reference", reference)); command.Parameters.Add(new SqlParameter("@paymenttype", paymenttype)); command.Parameters.Add(new SqlParameter("@amount", amount)); command.Parameters.Add(new SqlParameter("@paymentmethod", paymentmethod)); command.Parameters.Add(new SqlParameter("@employeename", employeename)); command.Parameters.Add(new SqlParameter("@updatetime", updatetime)); connect.Open(); command.ExecuteScalar(); connect.Close(); } catch { } } public void Load(string reference) { try { SqlConnection connect = new SqlConnection(connection); SqlCommand command = new SqlCommand("Payment_Join", connect); command.CommandType = CommandType.StoredProcedure; command.Parameters.Add(new SqlParameter("@Reference", reference)); //MessageBox.Show("ref = " + reference); connect.Open(); SqlDataReader reader = command.ExecuteReader(); while (reader.Read()) { this.reference = Convert.ToString(reader["nvReference"]); // MessageBox.Show(reference); // MessageBox.Show("here"); // MessageBox.Show("payment type id = " + reader["nvPaymentType"]); // MessageBox.Show("here1"); this.paymenttype = Convert.ToString(reader["nvPaymentType"]); // MessageBox.Show(paymenttype.ToString()); this.amount = Convert.ToDouble(reader["iAmount"]); this.paymentmethod = Convert.ToString(reader["nvMethod"]); this.employeename = Convert.ToString(reader["nvUsers"]); this.updatetime = Convert.ToDateTime(reader["tUpdateTime"]); } reader.Close(); } catch (Exception ex) { MessageBox.Show("Check it again" + ex); } } #endregion } } i have already binded the combo box items through designer, When i run the application i just get the reference populated in form 2 and combo box just populated not the particular value which is fetched. New to c# so help me to get familiar

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  • how do I integrate the aspnet_users table that comes with asp.net membership into my existing databa

    - by ooo
    i have a database that already has a users table COLUMNS: userID - int loginName - string First - string Last - string i just installed the asp.net membership table. Right now all of my tables are joined into my users table foreign keyed into the "userId" field How do i integrate asp.net_users table into my schema? here are the ideas i thought of: Add a membership_id field to my users table and on new inserts, include that new field in my users table. This seems like the cleanest way as i dont need to break any existing relationships. break all existing relationship and move all of the fields in my user table into the asp.net_users table. This seems like a pain but ultimately will lead to the most simple, normalized solution any thoughts?

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  • MSSQL Sum query

    - by ldb
    today my problem is this i have 2 column and i wish check if the sum of that columns isn't Higher then a value(485 for example) and if is do a query...i though to do SELECT * FROM table WHERE ColumnA+ColumnB<485 But isn't working... i've already tried with SELECT Sum(ColumnA)+Sum(ColumnB) AS Total FROM table but it gives me 1 column with the sum of all rows, i instead want a row for every sum. so how can i do..? xD i hope you understood if not just ask that i try to explain it better! and thanks in advice for who want to help me! EDIT: I Found out XD the problem was that the columns was Smallint and the result of 1 or more rows was more than 32k so it wasn't working! Thanks At all!!

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  • INSERT 0..n records into table 'A' based on content of table 'B' in MySql 5

    - by Robert Gowland
    Using MySql 5, I have a task where I need to update one table based on the contents of another table. For example, I need to add 'A1' to table 'A' if table 'B' contains 'B1'. I need to add 'A2a' and 'A2b' to table 'A' if table 'B' contains 'B2', etc.. In our case, the value in table 'B' we're interested is an enum. Right now I have a stored procedure containing a series of statements like: INSERT INTO A SELECT 'A1' FROM B WHERE B.Value = 'B1'; --Repeat for 'B2' -> 'A2a'; 'B2' -> 'A2b'; 'B3' -> 'A3', etc... Is there a nicer more DRY way of accomplishing this? Edit: There may be values in table 'B' that have no equivalent value for table 'A'.

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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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  • How to create unique user key

    - by Grayson Mitchell
    Scenario: I have a fairly generic table (Data), that has an identity column. The data in this table is grouped (lets say by city). The users need an identifier in order for printing on paper forms, etc. The users can only access their cites data, so if they use the identity column for this purpose they will see odd numbers (e.g. a 'New York' user might see 1,37,2028... as the listed keys. Idealy they would see 1,2,3... (or something similar) The problem of course is concurrency, this being a web application you can't just have something like: UserId = Select Count(*)+1 from Data Where City='New York' Has anyone come up with any cunning ways around this problem?

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  • Linq2SQL or EntityFramework and databinding

    - by rene marxis
    is there some way to do databinding with linq2SQL or EntityFramework using "typed links" to the bound property? Public Class Form1 Dim db As New MESDBEntities 'datacontext/ObjectContext Dim bs As New BindingSource Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load bs.DataSource = (From m In db.PROB_GROUP Select m) grid.DataSource = bs TextBox1.DataBindings.Add("Text", bs, "PGR_NAME") TextBox1.DataBindings.Add("Text", bs, db.PROB_GROUP) '**<--- Somthing like this** End Sub End Class I'd like to have type checking when compiling and the model changed.

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  • Sum of distinc rows after a 1-many table join

    - by Lock
    I have 2 tables that I am joining. Table 1 has 1-many relationship with table 2. That is, table 2 can return multiple rows for a single row of table 1. Because of this, the records of table 1 is duplicated for as many rows as are on table 2.. which is expected. Now, I have a sum on one of the columns from table 1, but because of the multiple rows that get returned on the join, the sum is obviously multiplying. Is there a way to get this number back to its original number? I tried dividing by the count of rows from table 2 but this didnt quite give me the expected result. Are there any analytical functions that could do this? I almost want something like "if this row has not yet been counted in the sum, add it to the sum"

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  • MySQL Rating system (calculating average from two tables).

    - by MussuR
    I have two tables, videos and videos_ratings. The videos table has an int videoid field (and many others but those fields are not important I think) and many records. The videos_ratings table has 3 int fields: videoid, rating, rated_by which has many records (multiple records for each fields from the videos table) but not for all records from the videos table. Currently I have the following mysql query: SELECT `videos`.*, avg(`videos_ratings`.`vote`) FROM `videos`, `videos_ratings` WHERE `videos_ratings`.`videoid` = `videos`.`videoid` GROUP BY `videos_ratings`.`videoid` ORDER BY RAND() LIMIT 0, 12 It selects all the records from table videos that have a rating in table video_ratings and calculates the average correctly. But what I need is to select all records from the videos table, no matter if there is a rating for that record or not. And if there aren't any records in the videos_ratings table for that particular videos record, the average function should show 0. Hope someone could understand what I want... :) Thanks!

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  • Change an autoincrementing field to one previous

    - by jlan
    One day, wordpress suddenly jumped from pots id 9110 to 890000000 post. Days later I'd like to move back new posts to continue from id 9111. I'm sure that id will never reach id 890000000, no problem here, but id is an autoincrement field and "ALTER TABLE wp8_posts AUTO_INCREMENT =9111" is not working. Can I force id to continue from 9111 ?

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  • Specify sorting order for a GROUP BY query to retrieve oldest or newest record for each group

    - by Beau Simensen
    I need to get the most recent record for each device from an upgrade request log table. A device is unique based on a combination of its hardware ID and its MAC address. I have been attempting to do this with GROUP BY but I am not convinced this is safe since it looks like it may be simply returning the "top record" (whatever SQLite or MySQL thinks that is). I had hoped that this "top record" could be hinted at by way of ORDER BY but that does not seem to be having any impact as both of the following queries returns the same records for each device, just in opposite order: SELECT extHwId, mac, created FROM upgradeRequest GROUP BY extHwId, mac ORDER BY created DESC SELECT extHwId, mac, created FROM upgradeRequest GROUP BY extHwId, mac ORDER BY created ASC Is there another way to accomplish this? I've seen several somewhat related posts that have all involved sub selects. If possible, I would like to do this without subselects as I would like to learn how to do this without that.

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  • Selecting rows distinctively

    - by noway
    Lets assume my database table structure is something like | items | weight | |============|==========| | item_1 | 50 | | item_2 | 90 | | item_2 | 45 | | item_2 | 60 | | item_3 | 40 | In the select statement, I want to show an item only for once with the highest weight also ordered by height. So the result should be : | items | weight | |============|==========| | item_2 | 90 | | item_1 | 50 | | item_3 | 40 | I tried something like SELECT DISTINCT items, weight FROM mytable ORDER BY weight DESC but it didn't work because the results are actually distinct. How can I make that selection?

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  • Transaction within a Transaction in C#

    - by Rosco
    I'm importing a flat file of invoices into a database using C#. I'm using the TransactionScope to roll back the entire operation if a problem is encountered. It is a tricky input file, in that one row does not necessary equal one record. It also includes linked records. An invoice would have a header line, line items, and then a total line. Some of the invoices will need to be skipped, but I may not know it needs to be skipped until I reach the total line. One strategy is to store the header, line items, and total line in memory, and save everything once the total line is reached. I'm pursuing that now. However, I was wondering if it could be done a different way. Creating a "nested" transaction around the invoice, inserting the header row, and line items, then updating the invoice when the total line is reached. This "nested" transaction would roll back if it is determined the invoice needs to be skipped, but the overall transaction would continue. Is this possible, practical, and how would you set this up?

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  • I want to do a sql update loop statement, by using the do--while in php

    - by Jean
    Hello, I want to loop the update statement, but it only loops once. Here is the code I am using: do { mysql_select_db($database_ll, $ll); $query_query= "update table set ex='$71[1]' where field='val'"; $query = mysql_query($query_query, $ll) or die(mysql_error()); $row_domain_all = mysql_fetch_assoc($query); } while ($row_query = mysql_fetch_assoc($query)); Thanks Jean

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  • Get previous and next row from current id

    - by Hukr
    How can I do to get the next row in a table? `image_id` int(11) NOT NULL auto_increment `image_title` varchar(255) NOT NULL `image_text` mediumtext NOT NULL `image_date` datetime NOT NULL `image_filename` varchar(255) NOT NULL If the current image is 3 for example and the next one is 7 etc. this won’t work: $query = mysql_query("SELECT * FROM images WHERE image_id = ".intval($_GET['id'])); echo $_GET['id']+1; How should I do? thanks

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  • How to avoid geometric slowdown with large Linq transactions?

    - by Shaul
    I've written some really nice, funky libraries for use in LinqToSql. (Some day when I have time to think about it I might make it open source... :) ) Anyway, I'm not sure if this is related to my libraries or not, but I've discovered that when I have a large number of changed objects in one transaction, and then call DataContext.GetChangeSet(), things start getting reaalllly slooowwwww. When I break into the code, I find that my program is spinning its wheels doing an awful lot of Equals() comparisons between the objects in the change set. I can't guarantee this is true, but I suspect that if there are n objects in the change set, then the call to GetChangeSet() is causing every object to be compared to every other object for equivalence, i.e. at best (n^2-n)/2 calls to Equals()... Yes, of course I could commit each object separately, but that kinda defeats the purpose of transactions. And in the program I'm writing, I could have a batch job containing 100,000 separate items, that all need to be committed together. Around 5 billion comparisons there. So the question is: (1) is my assessment of the situation correct? Do you get this behavior in pure, textbook LinqToSql, or is this something my libraries are doing? And (2) is there a standard/reasonable workaround so that I can create my batch without making the program geometrically slower with every extra object in the change set?

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  • multi-row update table with "different" data

    - by kralco626
    I think the best way to explain this is to tell you what I have. I have two tables A and B both have columns Field1 and Field2. However Field 2 is not populated in table B I want to populate field 2 of table B with field 2 of table A where field 1 of table A matches field 1 of table B. something like update tableB set Field2 = tableA.field2 where tablea.field1 = tableb.field1. The reason this may seem so odd and obscure is that I'm tyring to do an inital data load form an old database to a new one. please let me know if you need clarification

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  • help configuring a mail server for use with mail.jar and activation.jar

    - by bobbyblue
    im trying to work with the below code: import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import javax.mail.*; import javax.mail.internet.*; // important import javax.mail.event.*; // important import java.net.*; import java.util.*; public class servletmail extends HttpServlet { public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException { PrintWriter out=response.getWriter(); response.setContentType("text/html"); try { Properties props=new Properties(); props.put("mail.smtp.host","localhost"); // 'localhost' for testing Session session1 = Session.getDefaultInstance(props,null); String s1 = request.getParameter("text1"); //sender (from) String s2 = request.getParameter("text2"); String s3 = request.getParameter("text3"); String s4 = request.getParameter("area1"); Message message =new MimeMessage(session1); message.setFrom(new InternetAddress(s1)); message.setRecipients (Message.RecipientType.TO,InternetAddress.parse(s2,false)); message.setSubject(s3); message.setText(s4); Transport.send(message); out.println("mail has been sent"); } catch(Exception ex) { System.out.println("ERROR....."+ex); } } } im using mail.jar and activation.jar but i cant understand how shouls i configure it with a mail server which mail server should i use will i be able to send an email using above what are the requirements a mail server? how should i configure it

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