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  • mysql join table - selecting the newest row

    - by cmancre
    Hi, I have the following two MySQL tables TABLE NAMES NAME_ID NAME 1 name1 2 name2 3 name3 TABLE STATUS STATUS_ID NAME_ID TIMESTAMP 1 1 2010-12-20 12:00 2 2 2010-12-20 10:00 3 3 2010-12-20 10:30 4 3 2010-12-20 14:00 I would like to select all info from table NAMES and add most recent correspondent TIMESTAMP column from table STATUS RESULT NAME_ID NAME TIMESTAMP 1 name1 2010-12-20 12:00 2 name2 2010-12-20 10:00 3 name3 2010-12-20 14:00 Am stuck on this one. How do I left join only on the newer timestamp?

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  • Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

    - by DanM
    I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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  • My update query executes but doesn't update

    - by Kindson
    I have this update query. UPDATE production_shr_01 SET total_hours = hours, total_weight = weight, percentage = total_hours / 7893.3 WHERE (status = 'X') The query executes fine but the problem is that when this query executes, it doesn't update the percentage field. What might be the problem?

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  • Limit calls to external database with Python CGI

    - by Matt Ball
    I've got a Python CGI script that pulls data from a GPS service; I'd like this information to be updated on the webpage about once every 10s (the max allowed by the GPS service's TOS). But there could be, say, 100 users viewing the webpage at once, all calling the script. I think the users' scripts need to grab data from a buffer page that itself only upates once every ten seconds. How can I make this buffer page auto-update if there's no one directly viewing the content (and not accessing the CGI)? Are there better ways to accomplish this?

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  • Updating counters through Hibernate

    - by at
    This is an extremely common situation, so I'm expecting a good solution. Basically we need to update counters in our tables. As an example a web page visit: Web_Page -------- Id Url Visit_Count So in hibernate, we might have this code: webPage.setVisitCount(webPage.getVisitCount()+1); The problem there is reads in mysql by default don't pay attention to transactions. So a highly trafficked webpage will have inaccurate counts. The way I'm used to doing this type of thing is simply call: update Web_Page set Visit_Count=Visit_Count+1 where Id=12345; I guess my question is, how do I do that in Hibernate? And secondly, how can I do an update like this in Hibernate which is a bit more complex? update Web_Page wp set wp.Visit_Count=(select stats.Visits from Statistics stats where stats.Web_Page_Id=wp.Id) + 1 where Id=12345;

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  • Want to check fields for data fast.

    - by Tom
    We have a database setup that consists of two parts: a static structure, and dynamic additions. For each database, the dynamic can be different, and sometimes we don't have data for all the dynamic fields. Rigt now, we check for empties by looking at the total count of records in the entire table, but we want to move to a more refined method of checking for empties if possible. Is it possible to quickly check through several hundred fields and see which ones are empty and which ones are populated?

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  • how to select distinct rows for a column

    - by Satoru.Logic
    Hi, all. I have a table x that's like the one bellow: id | name | observed_value | 1 | a | 100 | 2 | b | 200 | 3 | b | 300 | 4 | a | 150 | 5 | c | 300 | I want to make a query so that in the result set I have exactly one record for one name: (1, a, 100) (2, b, 200) (5, c, 300) If there are multiple records corresponding to a name, say 'a' in the table above, I just pick up one of them. In my current implementation, I make a query like this: select x.* from x , (select distinct name, min(observed_value) as minimum_val from x group by name) x1 where x.name = x1.name and x.observed_value = x1.observed_value; But I think there may be some better way around, please tell me if you know, thanks in advance.

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  • How to first get different related values from diferent SQL tables (PHP)

    - by Ole Jak
    I am triig to fill options list. I have 2 tables USERS and STREAMS I vant to get all streams and get names of users assigned to that streams. Users consists of username and id Streams consists of id, userID, streamID I try such code: <?php global $connection; $query = "SELECT * FROM streams "; $streams_set = mysql_query($query, $connection); confirm_query($streams_set); $streams_count = mysql_num_rows($streams_set); while ($row = mysql_fetch_array($streams_set)){ $userid = $row['userID']; global $connection; $query2 = "SELECT email, username "; $query2 .= "FROM users "; $query2 .= "WHERE id = '{$userid}' "; $qs = mysql_query($query2, $connection); confirm_query($qs); $found_user = mysql_fetch_array($qs); echo ' <option value="'.$row['streamID'].'">'.$row['userID'].$found_user.'</option> '; } ?> But it does not return USER names from DB=( So what shall I do to this code to see usernames as "options" text?

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  • check if sqlserver is installed on a machine thro C#

    - by Skun
    Hey ! I am making an application which is a user interface to access 2 types of databases - SQLite and MSSQL server. The thing is, SQLite doesnt need to be "installed" since its just a flatfile database, but on the other hand, SQLserver (Express/normal) need to be installed before use. My Question is simple: Is there a way by which i can find out if an instance of SQLserver has been installed on the local machine by using a C# program?

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  • Multisite Enabling a Table

    - by Joe Fitzgibbons
    I am creating a table (table A) that will have a number of columns(of course) and there will be another table (table B) that holds metadata associated to rows in table A. I am working with a multi site implementation that has one database for the whole shabang. Rows in table A could belong to any number of sites but must belong to at least one. The problem I have is I am not sure what the best practice is for defining what site each row in table A belongs to. I want performance and scalability. There is no finite number of sites going forward. Rows in table A could belong to any number of sites in the future. Right now there are only 3. My initial thoughts are to have a primary site ID in Table A and then metadata in table B will have rows defining additional sites as needed. Another thought is to have a column in Table A for each site and it is a boolean as to wether it belongs to that site. Lastly I have thought about having another table to map rows in Table A to each site. What is the best way to associate rows in a table with any number of sites with performance and scalability in mind?

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  • Joining tables, if percentage is above certain value

    - by CluelessGerman
    My question is similar to this one: Compare rows and get percentage However, little different. I adapted my question to the other post. I got 2 tables. First table: user_id | post_id 1 1 1 2 1 3 2 12 2 15 And second table: post_id | rating 1 1 1 2 1 3 2 1 2 5 3 null 3 1 3 4 12 4 15 1 So now I would like to count the rating for each post, in the second table. If the rating has more than, lets say, 50% positive ratings than I want to get the post_id and going it to the post_id from table one and add 1 to the user_id. At the end it would return the user_id with the number of positive posts. The result for above table would be: user_id | helpfulPosts 1 2 2 1 The post with post_id 1 and 3 have positive rating, because more than 50% have ratings of 1-3. The post with id = 2 is not positive, because the rating is exactly 50%. How would I achieve this? For clarification: It's a mysql rdbm and a positive post, is one where the number of rating_ids with 1, 2 and 3 are more than half of the overall rating. Basically the same thing, from the other thread I posted above.

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  • oracle call stored procedure inside select

    - by CC
    Hi everybody. I'm working on a query (a SELECT) and I need to insert the result of this one in a table. Before doing the insert I have some checking to do, and if all columns are valid, I will do the insert. The checking is done in a stored procedure. The same procedure is used somewhere else too. So I'm thinking using the same procedure to do my checks. The procedure does the checkings and insert the values is all OK. I tryied to call the procedure inside my SELECT but it does not works. SELECT field1, field2, myproc(field1, field2) from MYTABLE. This kind of code does not works. I think it can be done using a cursor, but I would like to avoid the cursors. I'm looking for the easiest solution. Anybody, any idea ? Thanks alot. C.C.

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  • How to count number of occurences for all different values in database column?

    - by drasto
    I have a Postgre database that has say 10 columns. The fifth column is called column5. There are 100 rows in the database and possible values of column5 are c5value1, c5value2, c5value3...c5value29, c5value30. I would like to print out a table that shows how many times each value occurs. So the table would look like this: Value(of column5) number of occurrences of the value c5value1 1 c5value2 5 c5value3 3 c5value4 9 c5value5 1 c5value6 1 . . . . . . What is the command that does that? Thanks for help

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  • Worpress WorkFlow Modfications

    - by blgnklc
    Hi All WordPress Lovers, I would like to ask a help about Zensor which is a plugin that you publish a post then a moderator approves the post to be published on the wordpress blog site. When a post is awating for approval, each awaiting post is appearing "waiting moderation". But, I dont want any link appears before moderator approval. Actually I found the joing sentence below; 1- Must be added to the end of JOIN part of any query: LEFT JOIN wp_zensor ON ID = wp_zensor.post_id 2- Must be added to the end of WHERE condition : AND wp_zensor.moderation_status = 'approved' Could you please show me; where should I add these modification on the category link presentation below: <h2>Politics</h2> <?php $recent = new WP_Query("cat=31&showposts=1"); while($recent->have_posts()) : $recent->the_post();?> <b><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></b> <?php the_content_limit(140, "devami &raquo;"); ?> <div class="hppostmeta"> <p><?php the_time('j F Y, H:i'); ?> | <?php the_author_posts_link(); ?></p> </div> <?php endwhile; ?> Or any general solutions will be welcomed. Thanks. BK

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  • Database Optimization techniques for amateurs.

    - by Zombies
    Can we get a list of basic optimization techniques going (anything from modeling to querying, creating indexes, views to query optimization). It would be nice to have a list of these, one technique per answer. As a hobbyist I would find this to be very useful, thanks. And for the sake of not being too vague, let's say we are using a maintstream DB such as MySQL or Oracle, and that the DB will contain 500,000-1m or so records across ~10 tables, some with foreign key contraints, all using the most typical storage engines (eg: InnoDB for MySQL). And of course, the basics such as PKs are defined as well as FK contraints.

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  • Linqbuilder Query with an OrderBy

    - by Renshai
    I have a 1 : M relationship. I built a dynamic query based on input from users to return the listing of parents entities along with their children (using predicate builder: (done successfully new TDataContext().Ps.Where(predicate) )... but need to order the results by a field found only on the child entities. I'm at a loss: new TDataContext().Ps.Where(predicate).OrderBy(p = p.Cs. ??) where Ps = parents collection relationship with Cs = child entities any help appreciated.

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  • Where Not In OR Except simulation of SQL in LINQ to Object(C#)

    - by Thinking
    Suppose I have two lists that holds the list of source file names and destination file names respectively. The Sourcefilenamelist has files as 1.txt, 2.txt,3.txt, 4.txt while the Destinaitonlist has 1.txt,2.txt. I ned to write a linq query to find out which files are in SourceList that are absent in DestinationFile list. e.g. here the out put will be 3.txt and 4.txt. I have done this by a foreach statement.. but now I want to do the same by using LINQ(C#). Help needed. Thanks

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  • Cursor loops; How to perform something at start/end of loop 1 time only?

    - by James.Elsey
    I've got the following in one of my Oracle procedures, I'm using it to generate XML -- v_client_addons is set to '' to avoid null error OPEN C_CLIENT_ADDONS; LOOP FETCH C_CLIENT_ADDONS INTO CLIENT_ADDONS; EXIT WHEN C_CLIENT_ADDONS%NOTFOUND; BEGIN v_client_addons := v_client_addons || CLIENT_ADDONS.XML_DATA; END; END LOOP; CLOSE C_CLIENT_ADDONS; -- Do something later with v_client_addons The loop should go through my cursor and pick out all of the XML values to display, such as : <add-on name="some addon"/> <add-on name="another addon"/> What I would like to achieve is to have an XML start/end tag inside this loop, so I would have the following output <addons> <add-on name="some addon"/> <add-on name="another addon"/> </addons> How can I do this without having the <addons> tag after every line? If there are no addons in the cursor (cursor is empty), then I would like to skip this part enitrely

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  • View Lambdas in Visual Studio Debugger

    - by Vaccano
    I have the a simple LinqToSQL statement that is not working. Something Like this: List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false) .ToList(); I look at _ctx.DBList in the debugger and the second item fits both parameters. Is there a way I can dig into this more to see what is going wrong?

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