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  • MySQL customized join query using multiple tables

    - by itgeek
    I am searching one student from each class from one group. There are different class groups and every group has different classes and every class has multiple students. See below: Group1 --> Class1, Class2 etc Class1 --> GreenStudent1, GreenStudent2 etc Class2 --> RedStudent1, RedStudent2 etc ------------------------------------------------------ SELECT table1.id, table1.myname, table1.marks table2.studentid, table2.studentname FROM table1 INNER JOIN table3 ON table1.oldid = table3.id INNER JOIN table2 ON table2.studentid = table3.newid WHERE table1.classgroup = 'SCI79' GROUP BY table1.oldid ORDER BY table1.marks DESC There are different joins applied in the query. Above mentioned query giving me correct results but I need little modification in it. Current query returning me one student from each class. What I need? I need one student from each class but only that student who has MAXIMUM table1.marks So I should have one student from each class who has maximum number in their relevant classes. Can anyone suggest some solution or rewrite this query? Thanks :)

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  • mysql syntax how to add a third table to $query

    - by IberoMedia
    I have code: $query = "SELECT a.*, c.name as categoryname, c.id as categoryid". " FROM #__table_one as a". " LEFT JOIN #__table_two c ON c.id = a.catid"; $query .= " WHERE a.published = 1" ." AND a.access <= {$aid}" ." AND a.trash = 0" ." AND c.published = 1" ." AND c.access <= {$aid}" ." AND c.trash = 0" ; I would like to add a third table ('__some_table') for the parts of the query where a.publish, a.access and a.trash. In other words, I want these fields to be retrieved from another table, not "#__table_one", but I do not know how to incorporate the #__some_table into the current query I imagine the JOIN command can help me, but I do not know how to code mysql Thank you,

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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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  • Potential Django Bug In QuerySet.query?

    - by Mike
    Disclaimer: I'm still learning Django, so I might be missing something here, but I can't see what it would be... I'm running Python 2.6.1 and Django 1.2.1. (InteractiveConsole) >>> from myproject.myapp.models import * >>> qs = Identifier.objects.filter(Q(key="a") | Q(key="b")) >>> print qs.query SELECT `app_identifier`.`id`, `app_identifier`.`user_id`, `app_identifier`.`key`, `app_identifier`.`value` FROM `app_identifier` WHERE (`app_identifier`.`key` = a OR `app_identifier`.`key` = b ) >>> Notice that it doesn't put quotes around "a" or "b"! Now, I've determined that the query executes fine. So, in reality, it must be doing so. But, it's pretty annoying that printing out the query prints it wrong. Especially if I did something like this... >>> qs = Identifier.objects.filter(Q(key=") AND") | Q(key="\"x\"); DROP TABLE `app_identifier`")) >>> print qs.query SELECT `app_identifier`.`id`, `app_identifier`.`user_id`, `app_identifier`.`key`, `app_identifier`.`value` FROM `app_identifier` WHERE (`app_identifier`.`key` = ) AND OR `app_identifier`.`key` = "x"); DROP TABLE `app_identifier` ) >>> Which, as you can see, not only creates completely malformed SQL code, but also has the seeds of a SQL injection attack. Now, obviously this wouldn't actually work, for quite a number of reasons (1. The syntax is all wrong, intentionally, to show the oddity of Django's behavior. 2. Django won't actually execute the query like this, it will actually put quotes and slashes and all that in there like it's supposed to). But, this really makes debugging confusing, and it makes me wonder if something's gone wrong with my Django installation. Does this happen for you? If so/not, what version of Python and Django do you have? Any thoughts?

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  • Results from two queries at once in sqlite?

    - by SF.
    I'm currently trying to optimize the sluggish process of retrieving a page of log entries from the SQLite database. I noticed I almost always retrieve next entries along with count of available entries: SELECT time, level, type, text FROM Logs WHERE level IN (%s) ORDER BY time DESC, id DESC LIMIT LOG_REQ_LINES OFFSET %d* LOG_REQ_LINES ; together with total count of records that can match current query: SELECT count(*) FROM Logs WHERE level IN (%s); (for a display "page n of m") I wonder, if I could concatenate the two queries, and ask them both in one sqlite3_exec() simply concatenating the query string. How should my callback function look then? Can I distinguish between the different types of data by argc? What other optimizations would you suggest?

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  • Access database query locks ability to edit table?

    - by Sattvic
    I created a query in Microsoft Access like the one below: SELECT Deliverables.ID, Deliverables.Title, Deliverables.Summary, Deliverables.Header_Code, Deliverables.Header_Code.Value, Deliverables.Sort_order, Deliverables.Pillar, Deliverables.Pillar.Value, Deliverables.Misc_ID FROM Deliverables WHERE (((Deliverables.Pillar.Value)="Link Building")); But my problem is that this query locks my fields and I cannot make changes to the table using the query view. Any suggestions? I am using Microsoft Access 2007

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  • SQL query not working

    - by Ziv
    hi, I'm trying to create a query in an access database for a C# dataset using the query editor but the created method says there is a problem and isn't created correctly. SELECT Discs.* FROM Discs WHERE (Title=@Title OR @Title IS NULL) AND (Type=@Type OR @Type IS NULL) AND (ContainerID=@ContainerID OR @ContainerID IS NULL) AND NOT (@Title IS NULL AND @Type IS NULL AND @ContainerID IS NULL) the error is: Generated SELECT statement. Error in WHERE clause near '@'. Unable to parse query text. the generated select method doesn't have any parameters and is unusable. I've tried the exact same SQL statement in the access query and it worked flawlessly, what am I supposed to be doing differently when transferring it to C#?

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  • SQL: Limit rows linked to each joined row

    - by SolidSnakeGTI
    Hello, 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. I'm using MySQL 4.1+, but if you know the answer for another engine, just share. Appreciated advice in advance :)

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  • hadoop - large database query

    - by Mastergeek
    Situation: I have a Postgres DB that contains a table with several million rows and I'm trying to query all of those rows for a MapReduce job. From the research I've done on DBInputFormat, Hadoop might try and use the same query again for a new mapper and since these queries take a considerable amount of time I'd like to prevent this in one of two ways that I've thought up: 1) Limit the job to only run 1 mapper that queries the whole table and call it good. or 2) Somehow incorporate an offset in the query so that if Hadoop does try to use a new mapper it won't grab the same stuff. I feel like option (1) seems more promising, but I don't know if such a configuration is possible. Option(2) sounds nice in theory but I have no idea how I would keep track of the mappers being made and if it is at all possible to detect that and reconfigure. Help is appreciated and I'm namely looking for a way to pull all of the DB table data and not have several of the same query running because that would be a waste of time.

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  • FreeText COUNT query on multiple tables is super slow

    - by Eric P
    I have two tables: **Product** ID Name SKU **Brand** ID Name Product table has about 120K records Brand table has 30K records I need to find count of all the products with name and brand matching a specific keyword. I use freetext 'contains' like this: SELECT count(*) FROM Product inner join Brand on Product.BrandID = Brand.ID WHERE (contains(Product.Name, 'pants') or contains(Brand.Name, 'pants')) This query takes about 17 secs. I rebuilt the FreeText index before running this query. If I only check for Product.Name. They query is less then 1 sec. Same, if I only check the Brand.Name. The issue occurs if I use OR condition. If I switch query to use LIKE: SELECT count(*) FROM Product inner join Brand on Product.BrandID = Brand.ID WHERE Product.Name LIKE '%pants%' or Brand.Name LIKE '%pants%' It takes 1 secs. I read on MSDN that: http://msdn.microsoft.com/en-us/library/ms187787.aspx To search on multiple tables, use a joined table in your FROM clause to search on a result set that is the product of two or more tables. So I added an INNER JOINED table to FROM: SELECT count(*) FROM (select Product.Name ProductName, Product.SKU ProductSKU, Brand.Name as BrandName FROM Product inner join Brand on product.BrandID = Brand.ID) as TempTable WHERE contains(TempTable.ProductName, 'pants') or contains(TempTable.BrandName, 'pants') This results in error: Cannot use a CONTAINS or FREETEXT predicate on column 'ProductName' because it is not full-text indexed. So the question is - why OR condition could be causing such as slow query?

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  • Speed up csv export when using php from mysql database query

    - by John
    Ok, so i've got a web system (built on codeigniter & running on mysql) that allows people to query a database of postal address data by making selections in a series of forms until they arrive at the selection that want, pretty standard stuff. They can then buy that information and download it via that system. The queries run very fast, but when it comes to applying that query to the database,and exporting it to csv, once the datasets get to around the 30,000 record mark (each row has around 40 columns of which about 20 are all populated with on average 20 chars of data per cell) it can take 5 or so minutes to export to csv. So, my question is, what is the main cause for the slowness? Is it that the resultset of data from the query is so large, that it is running into memory issues? Therefore should i allow much more memory to the process? Or, is there a much more efficient way of exporting to csv from a mysql query that i'm not doing? Should i save the contents of the query to a temp table and simply export the temp table to csv? Or am i going about this all wrong? Also, is the fact that i'm using Codeigniters Active Record for this prohibitive due to the way that it stores the resultset? Any advice is welcome! Thank you for reading!

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  • Query MS Access database in VB 2008

    - by Logan
    Hi, I added an Access database as a Data Source in VB 2008. I want to query this database and use the information in various ways throughout the program. For example, there is an Employee table with first/last names of employees. I have a combobox on my form that I want to display all of the employees. So I want to query the database for all the rows in the Employee table, and add them to the combobox as I go. I am familiar with SQL Syntax, so I am not asking how to write the query itself, but rather how to fetch rows in VB code (mimicking php's mysql_fetch_assoc and mysql_connect essentially) Thanks! Edit: Also, I want to know if I can query a DB if I don't add it as a data source (if I know the path name of the database)

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  • MySQL: Query Cacheing (How do I use memcache?)

    - by Rachel
    I have an query like: SELECT id as OfferId FROM offers WHERE concat(partycode, connectioncode) = ? AND CURDATE() BETWEEN offer_start_date AND offer_end_date AND id IN ("121211, 123341,151512,5145626 "); Now I want to cache the results of this query using memcache and so my question is How can I cache an query using memcache. I am currently using CURDATE() which cannot be used if we want to implement caching and so how can I get current date functionality without using CURDATE() function ?

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  • SQL: Interrupting a query

    - by NoozNooz42
    I've worked on a project using a proprietary non-SQL DB where queries could be interrupted and in the codebase there were quite some spots where that functionnality was used and made perfect sense (for example to stop a long running query that gets cancelled by the user, or when a more recent query takes place and renders the previous query obsolete, etc.) and I realized I never really saw that kind of "interrupted queries" previously and thought it could make a good SO question (several questions, but they're all related to exactly the same thing): can SQL queries be interrupted? is this part of the SQL standard? if it's not part of the SQL standard, which SQL DBs allow queries to be interrupted (any example most welcome)? is it common to interrupt a DB query (SQL or not) which you'll know you won't care about the result anymore? (in the codebase I've worked on, it sure helps lighten the server's load)

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  • What scenarios/settings will result in a query on SQL Server (2008) return stale data

    - by s1mm0t
    Most applications rarely need to display 100% accurate data. For example if this stack overflow question displays that there have been 0 views, when there have really been 10, it doesn't really matter. This is one way that the (perceived) performance of applications can be improved, by caching results and therefore sometimes not showing 100% accurate results. There are some cases where the data does need to be 100% accurate though. So if I run the query select * from Foo I want to be sure that the results are not stale. Now depending on how my database is set up, other activity on the database, use of transactions and isolation levels etc this query may or may not be a true reflection of the world. What scenario's and settings can people think of that will result in this query returning stale results or given that another connection is part way through a transaction that has updated this table, how can I guarantee that when the above query returns, the results will be accurate.

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  • MySQL Query : Advise Needed.

    - by Rachel
    "SELECT id as Id from dbTable WHERE code = ? AND CURDATE() BETWEEN start_date AND end_date AND offerId IN ('12321', '12124')"; //Passing arguments for the query $args = array_merge(array(51342),$offerid); //Execute the prepared query $statement->execute($args); Now array(51342) represents combination of code+value, aside my database has value, code columns and so I want a query which would look logically like "SELECT id as Id from dbTable WHERE code and value (Note here I do not know the syntax, what am looking at is (code+value = ?), please advise on query) = ? AND CURDATE() BETWEEN start_date AND end_date AND offerId IN ('12321', '12124')";

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  • Optimize MySQL database query

    - by rajeeesh
    I had a commenting application in my web site. The comments will store in a MySQL table . table structure as follows id | Comment | user | created_date ------------------------------------------------------ 12 | comment he | 1245 | 2012-03-30 12:15:00 ------------------------------------------------------ I need to run a query for listing all the comments after a specific time. ie .. a query like this SELECT * FROM comments WHERE created_date > "2012-03-29 12:15:00" ORDER BY created_date DESC Its working fine.. My question is if I got a 1-2 lakh entry in this table is this query is sufficient for the purpose ? or this query will take time to execute ? In most cases I have to show last 2 days data + periodically ( interval of 10 mins ) checking for updates with ajax from this table ... Please help Thanks

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  • Running a Query in SQL Plus

    - by WENzER
    Hi, I have to run a query in the loop in SQLPLUS. and the count of loop is coming from some other SQL query. So i have to declared a variable which will take the value of count. Now I want to use this variable in my query. How would i be able to do the same . Please suggest me Thanks in advance

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  • stepping into a linq query

    - by MyNameIsJob
    Is it possible to step into a linq query? I have a linq to entity framework 4 query in it's simplest form: List = List.Where(f => f.Value.ToString().ToLowerInvariant().Contains(filter.ToLowerInvariant())); It's a query against an Entity Framework DbContext and I'm having trouble seeing why it works for something like: List searching for 001 yields no results against the following list Test001 Test002 Test003 Test004 However any other search yields results (Such as t00 or Test) I was hoping to figure out a way to see the resulting sql but it appears that I need Intellitrace, which I don't currently have or possibly stepping through the query itself and see each iteration build itself.

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  • This query show me with this active record

    - by New Kid
    I am having trouble getting two tables and passing them to controller: IN A MODEL: function get_all_entries() { $query = $this->db->get('entry'); return $query->result(); $this->db->select('entry_id , count(comment_id) as total_comment'); $this->db->group_by('entry_id'); $comment = $this->db->get('comment'); return $comment->result(); } IN A CONTROLLER: $data['query'] = $this->blog_model->get_all_entries(); $this->load->view('blog/index',$data); How do I return $query and $comment variables to controller? I think I am doing it wrong.

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  • How to execute query with empty fields?

    - by Kliver Max
    I have a SQL Query: SELECT documents.*, t_rights.rights, documents_list.docs FROM documents INNER JOIN t_rights on t_rights.num=documents.type_right INNER JOIN documents_list on documents_list.num=documents.document1 WHERE code_document=1 or code_document=1 In case if i have fields documents.document1 and documents.document1 with some value all works fine. But if this field empty i get empty query result. Its possible make query like this with empty fields?

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  • My $query->fetch() doesn't work

    - by Tae
    Question edited following the comments. It still doesn't work. Hi there, I'm trying to learn how PDO works, but my script: $database = new PDO('mysql:host=localhost;dbname=***', '***', '***'); $query = $database->prepare("SELECT nombre, tecnica, tamanno, estado FROM obra WHERE anno = ?"); $query->execute(array('2009')); while ($item = $query->fetch(PDO::FETCH_ASSOC)) { $item['nombre']; } Prints nothing. If I do: var_dump($query->fetch()) I get bool(false). After reading lots of examples I can't figure out what I'm doing wrong. Thanks in advance.

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  • How to set the delay between update queries in Mysql so that every query get executed succesfully?

    - by OM The Eternity
    Hi All I have to the Update query mulitple times for different parameters using for loop in my PHP Script, now the problem Is Whenever I do it, only my last query get executed, all the previous queries seems to be skipped. the loop goes like this: foreach($cntrlflagset as $cntrlordoc => $cntrlorflag){ for($t=0;$t<count($cntrlorflag);$t++){ $userlvl = "controller"; $docflag = 1; $postfix = "created"; $createdoc->updatedocseeflags($cntrlorflag[$t],$docflag,$cntrlordoc,$postfix,$userlvl); $docflag = 2; $postfix = "midlvl"; $createdoc->updatedocseeflags($cntrlorflag[$t],$docflag,$cntrlordoc,$postfix,$userlvl); } } Here, the called function $createdoc-updatedocseeflags($cntrlorflag[$t],$docflag,$cntrlordoc,$postfix,$userlvl); Contains the Update query: $query = "UPDATE tbl_docuserstatus SET"; //if($flag != ""){ $query .= " docseeflag_".$postfix." = '".$flag."'"; //} $query .= " WHERE doc_id = '".$doc_id."' AND user_id = '".$user_id."'"; if($userlvl == "midlvl"){ $query .= " AND doc_midlvluser = '1'"; }elseif($userlvl == "finallvl"){ $query .= " AND doc_finallvluser = '1'"; }elseif($userlvl == "creator"){ $query .= " AND doc_creator = '1'"; }elseif($userlvl == "controller"){ $query .= " AND doc_controller = '1'"; }elseif($docarchive == 1){ $query .= " AND doc_controller = '1'"; } So could some one tell me, How to set the delay between update queries in Mysql so that every query get executed succesfully? Thanks In Advance

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  • MySQL Query Problem

    - by user559744
    Hello guys, I'm getting following error message. Please help me. Thanks Notice: Trying to get property of non-object in C:\xampp\htdocs\my\include\user_functions.php on line 34 Here is my Code $conn = db_connection(); if($conn == false) { user_error('Unable to connect to database'); return false; } $query = "UPDATE user SET passwd = '".$new_passwd."' WHERE username = '".$username."' "; $result=$conn->query($query); if($result == false) { user_error('Query Error'.$conn->error); return false; } if($result->num_rows == 1) { echo 'Password changed'; } else { echo 'Failed '; } here is my db_connection function db_connection() { $db = new mysqli('localhost','root','','php_login'); if(!$db) { echo 'Could not connect to database server'; } else { return $db; } }

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  • Data binding directly to a store query (DbSet, DbQuery, DbSqlQuery) is not supported.

    - by Chandradev
    HiI was doing some test with code first approach in EF. Then while populating the Gridview i was getting error like thisData binding directly to a store query (DbSet, DbQuery, DbSqlQuery) is not supported. Instead populate a DbSet with data, for example by calling Load on the DbSet, and then bind to local data. For WPF bind to DbSet.Local. For WinForms bind to DbSet.Local.ToBindingList().For solving this error we have to write the code like this private void FillGrid()        {            using (var Context = new EmpDatabaseContext())            {                var query = Context.Emps.Select(m => m);                //var query = from m in Context.Emps                //            select m;               // Gridview1.DataSource = query;                Gridview1.DataSource = query.ToList();                Gridview1.DataBind();            }        }  We canot bind Iqueryable directly. We have to change into ToList()

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