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• Generate lags R

  - by Btibert3

  Hi All, I hope this is basic; just need a nudge in the right direction. I have read in a database table from MS Access into a data frame using RODBC. Here is a basic structure of what I read in: PRODID PROD Year Week QTY SALES INVOICE Here is the structure: str(data) 'data.frame': 8270 obs. of 7 variables: $ PRODID : int 20001 20001 20001 100001 100001 100001 100001 100001 100001 100001 ... $ PROD : Factor w/ 1239 levels "1% 20qt Box",..: 335 335 335 128 128 128 128 128 128 128 ... $ Year : int 2010 2010 2010 2009 2009 2009 2009 2009 2009 2010 ... $ Week : int 12 18 19 14 15 16 17 18 19 9 ... $ QTY : num 1 1 0 135 300 270 300 270 315 315 ... $ SALES : num 15.5 0 -13.9 243 540 ... $ INVOICES: num 1 1 2 5 11 11 10 11 11 12 ... Here are the top few rows: head(data, n=10) PRODID PROD Year Week QTY SALES INVOICES 1 20001 Dolie 12" 2010 12 1 15.46 1 2 20001 Dolie 12" 2010 18 1 0.00 1 3 20001 Dolie 12" 2010 19 0 -13.88 2 4 100001 Cage Free Eggs 2009 14 135 243.00 5 5 100001 Cage Free Eggs 2009 15 300 540.00 11 6 100001 Cage Free Eggs 2009 16 270 486.00 11 7 100001 Cage Free Eggs 2009 17 300 540.00 10 8 100001 Cage Free Eggs 2009 18 270 486.00 11 9 100001 Cage Free Eggs 2009 19 315 567.00 11 10 100001 Cage Free Eggs 2010 9 315 569.25 12 I simply want to generate lags for QTY, SALES, INVOICE for each product but I am not sure where to start. I know R is great with Time Series, but I am not sure where to start. I have two questions: 1- I have the raw invoice data but have aggregated it for reporting purposes. Would it be easier if I didn't aggregate the data? 2- Regardless of aggregation or not, what functions will I need to loop over each product and generate the lags as I need them? In short, I want to loop over a set of records, calculate lags for a product (if possible), append the lags (as they apply) to the current record for each product, and write the results back to a table in my database for my reporting software to use. Any help you can provide will be greatly appreciated! Many thanks in advance, Brock

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• Improving performance on data pasting 2000 rows with validations

  - by Lohit

  I have N rows (which could be nothing less than 1000) on an excel spreadsheet. And in this sheet our project has 150 columns like this: Now, our application needs data to be copied (using normal Ctrl+C) and pasted (using Ctrl+V) from the excel file sheet on our GUI sheet. Copy pasting 1000 records takes around 5-6 seconds which is okay for our requirement, but the problem is when we need to make sure the data entered is valid. So we have to validate data in each row generate appropriate error messages and format the data as per requirement. So we need to at runtime parse and evaluate data in each row. Now all the formatting of data and validations come from the back-end database and we have it in a data-table (dtValidateAndFormatConditions). The conditions would be around 50. So you can see how slow this whole process becomes since N X 150 X 50 operations are required to complete this whole process. Initially it took approximately 2-3 minutes but now i have reduced it to 20 - 30 seconds. However i have increased the speed by making an expression parser of my own - and not by any algorithm, is there any other way i can improve performance, by using Divide and Conquer or some other mechanism. Currently i am not really sure how to go about this. Here is what part of my code looks like: public virtual void ValidateAndFormatOnCopyPaste(DataTable DtCopied, int CurRow) { foreach (DataRow dRow in dtValidateAndFormatConditions.Rows) { string Condition = dRow["Condition"]; string FormatValue = Value = dRow["Value"]; GetValidatedFormattedData(DtCopied,ref Condition, ref FormatValue ,iRowIndex); Condition = Parse(Condition); dRow["Condition"] = Condition; FormatValue = Parse(FormatValue ); dRow["Value"] = FormatValue; } } The above code gets called row-wise like this: public override void ValidateAndFormat(DataTable dtChangedRecords, CellRange cr) { int iRowStart = cr.Row, iRowEnd = cr.Row + cr.RowCount; for (int iRow = iRowStart; iRow < iRowEnd; iRow++) { ValidateAndFormatOnCopyPaste(dtChangedRecords,iRow); } } Please know my question needs a more algorithmic solution than code optimization, however any answers containing code related optimizations will be appreciated as well. (Tagged Linq because although not seen i have been using linq in some parts of my code).

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• SQL Server 2008: If Multiple Values Set In Other Mutliple Values Set

  - by AJH

  In SQL, is there anyway to accomplish something like this? This is based off a report built in SQL Server Report Builder, where the user can specify multiple text values as a single report parameter. The query for the report grabs all of the values the user selected and stores them in a single variable. I need a way for the query to return only records that have associations to EVERY value the user specified. -- Assume there's a table of Elements with thousands of entries. -- Now we declare a list of properties for those Elements to be associated with. create table #masterTable ( ElementId int, Text varchar(10) ) insert into #masterTable (ElementId, Text) values (1, 'Red'); insert into #masterTable (ElementId, Text) values (1, 'Coarse'); insert into #masterTable (ElementId, Text) values (1, 'Dense'); insert into #masterTable (ElementId, Text) values (2, 'Red'); insert into #masterTable (ElementId, Text) values (2, 'Smooth'); insert into #masterTable (ElementId, Text) values (2, 'Hollow'); -- Element 1 is Red, Coarse, and Dense. Element 2 is Red, Smooth, and Hollow. -- The real table is actually much much larger than this; this is just an example. -- This is me trying to replicate how SQL Server Report Builder treats -- report parameters in its queries. The user selects one, some, all, -- or no properties from a list. The written query treats the user's -- selections as a single variable called @Properties. -- Example scenario 1: User only wants to see Elements that are BOTH Red and Dense. select e.* from Elements e where (@Properties) --ideally a set containing only Red and Dense in (select Text from #masterTable where ElementId = e.Id) --ideally a set containing only Red, Coarse, and Dense --Both Red and Dense are within Element 1's properties (Red, Coarse, Dense), so Element 1 gets returned, but not Element 2. -- Example scenario 2: User only wants to see Elements that are BOTH Red and Hollow. select e.* from Elements e where (@Properties) --ideally a set containing only Red and Hollow in (select Text from #masterTable where ElementId = e.Id) --Both Red and Hollow are within Element 2's properties (Red, Smooth, Hollow), so Element 2 gets returned, but not Element 1. --Example Scenario 3: User only picked the Red option. select e.* from Elements e where (@Properties) --ideally a set containing only Red in (select Text from #masterTable where ElementId = e.Id) --Red is within both Element 1 and Element 2's properties, so both Element 1 and Element 2 get returned. The above syntax doesn't actually work because SQL doesn't seem to allow multiple values on the left side of the "in" comparison. Error that returns: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. Am I even on the right track here? Sorry if the example looks long-winded or confusing.

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• how to design this relation in a DB schema

  - by raticulin

  I have a table Car in my db, one of the columns is purchaseDate. I want to be able to tag every car with a number of Policies (limited to 10 policies). Each policy has a time to life (ttl, a duration of time, like '5 years', '10 months' etc), that is, for how long since the car's purchaseDate the policy can be applied. I need to perform the following actions: when inserting a Car, it will be set with a number of Policies (at least one is set) sometimes a Car will be updated to add/remove a Policy searches must be done taking into account date/policies, for example: 'select all cars that are not covered by any policy as of today' My current design is (pol0..pol9 are the policies): CREATE TABLE Car ( id int NOT NULL IDENTITY(1,1), purchaseDate datetime NOT NULL, //more stuff... pol0 smallint default NULL, pol1 smallint default NULL, pol2 smallint default NULL, pol3 smallint default NULL, pol4 smallint default NULL, pol5 smallint default NULL, pol6 smallint default NULL, pol7 smallint default NULL, pol8 smallint default NULL, pol9 smallint default NULL, PRIMARY KEY (id) ) CREATE TABLE Policy ( id smallint NOT NULL, name varchar(50) collate Latin1_General_BIN NOT NULL, ttl varchar(100) collate Latin1_General_BIN NOT NULL, PRIMARY KEY (id) ) The problem I am facing is that the sql to perform the query above is a nightmare to write. As I don't know in which column each policy can be, so I have to check all columns for every policy etc etc. So I am wondering wether it is worth changing this. My questions are: The smallint as Policy id was chosen instead of an 'int IDENTITY' in order to save some space as there are going to be millions of Car records. It just adds complexity when creating a Policy as we must handle the id etc. Was it worth doing this? I am thinking that maybe there is a much better design? Obviously we could move the policy/car relation to its own table CarPolicy, benefits would be: no limit on 10 policies per car adding/removing etc much easier when only the default policy is applied (when no others are applied one called Default policy is applied), we could signal that by not having any entry in CarPolicy, now this is just done inserting the Default policy id in one of the columns. The cons are that we would need to change the DB, ORM classes etc. What would you recommend? Maybe there is another smart way to implement this that we are not aware without using the CarPolicy table?

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• Perl ftp question, like the previous ones ...

  - by Jerry Scott

  I need to move or copy a simple text file from one web site to another web site. I have administrator rights to both web sites. The first web site has a large data file (again, just a text file), certain records are selected and written to a team file (for entry into a tournament). Next I go through paypal and pay for the entries. The second site is for the the club running the tournament and I use IPN to return to a script on their site and if it verified, I add the team memebers into the master file for the tournament. I am limited to the ONE IPN script on the tournament site because I have a ton of other entries that come in from all over. The first site has the rosters for the state and no need to type all that data from each club, use the rosters like I use for all the non-paypal tounamenmts. I can ftp the team file to the second server and place it in the folder just like it was created from scratch from that server originally and everything should go fine but I took the examples and tried them and nothing. Here's the code section: my $custom = $in->param('custom'); my $filename = "$ENV{DOCUMENT_ROOT}/database/$custom"; my $usjochost = '208.109.14.105'; my $okserieshost = '208.109.181.196'; my $usjocuser = 'teamentry'; my $okseriesuser = 'okwaentry'; my $usjocpw = 'Password1'; my $okseriespw = 'Password1'; my $file = $custom; my $usjocpath ='/home/content/u/s/j/usjoc/html/database/'; my $okseriespath ='/home/content/o/k/s/okseries/html/database/'; $ftp = Net::FTP->new($okserieshost, Debug => 0) or die "Could not connect to '$okserieshost': $@"; $ftp->login($okseriesuser, $okseriespw) or die sprintf "Could not login: %s", $ftp->message; #$ftp->cwd(/database) or die sprintf "Could not login: %s", $ftp->message; $ftp->get($filename); #$ftp = Net::FTP->new($usjochost, Debug => 0) or die "Could not connect to '$usjochost': $@"; $ftp->quit; I NEED to READ the file on the first web site (okseries.com) and write the file on the second web site (usjoc.com). I have no problem reading and writing the file on the server, is sending the file to the second server. HELP! I'm not a genius at PERL.

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• MySQL - Calculating fields on the fly vs storing calculated data

  - by Christian Varga

  Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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• List of checkboxes

  - by Andrea Girardi

  Hi all, Happy New Year to all. I'm a newbie in VB.NET and ASP.NET. This is my problem: I retrieve a list of records from DB and, for every row, I need to show 4 checkboxes. I can use a checkboxlist for every rows, but it's not so clear how I can process the results after the submit. I've some object and some operations available for that object. From database I extract a list of object with all operations. For every operation I want to show a check box to enable or disable the operation. The result is something like that: OBJ1 - url - [] [x] [] OBJ2 - url - [] [x] [x] On url I've an href to another page created using the Id retrieved from DB. To create that I used this code: <td class="column-filename"> <strong> <asp:Label runat="server" Text='<%#DataBinder.Eval(Container.DataItem, "GroupName")%>'></asp:Label> </strong> </td> <td align="left"> <span style="vertical-align:middle"> <asp:CheckBoxList runat="server" ID="operations" RepeatDirection="Horizontal" RepeatLayout="Table"> <asp:ListItem Text="View"></asp:ListItem> <asp:ListItem Text="Upload"></asp:ListItem> <asp:ListItem Text="Move"></asp:ListItem> <asp:ListItem Text="Delete"></asp:ListItem> <asp:ListItem Text="Rename"></asp:ListItem> <asp:ListItem Text="Replace"></asp:ListItem> </asp:CheckBoxList> </span> </td> </asp> </asp> my problem is: how can I parse all checkboxes? could you help me or send me a link or any other resources to solve my issue? many thanks! Andrea

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• What to Expect in Rails 4

  - by mikhailov

  Rails 4 is nearly there, we should be ready before it released. Most developers are trying hard to keep their application on the edge. Must see resources: 1) @sikachu talk: What to Expect in Rails 4.0 - YouTube 2) Rails Guides release notes: http://edgeguides.rubyonrails.org/4_0_release_notes.html There is a mix of all major changes down here: ActionMailer changes excerpt: Asynchronously send messages via the Rails Raise an ActionView::MissingTemplate exception when no implicit template could be found ActionPack changes excerpt Added controller-level etag additions that will be part of the action etag computation Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) Add Routing Concerns to declare common routes that can be reused inside others resources and routes Added ActionController::Live. Mix it in to your controller and you can stream data to the client live truncate now always returns an escaped HTML-safe string. The option :escape can be used as false to not escape the result Added ActionDispatch::SSL middleware that when included force all the requests to be under HTTPS protocol ActiveModel changes excerpt AM::Validation#validates ability to pass custom exception to :strict option Changed `AM::Serializers::JSON.include_root_in_json' default value to false. Now, AM Serializers and AR objects have the same default behaviour Added ActiveModel::Model, a mixin to make Ruby objects work with AP out of box Trim down Active Model API by removing valid? and errors.full_messages ActiveRecord changes excerpt Use native mysqldump command instead of structure_dump method when dumping the database structure to a sql file. Attribute predicate methods, such as article.title?, will now raise ActiveModel::MissingAttributeError if the attribute being queried for truthiness was not read from the database, instead of just returning false ActiveRecord::SessionStore has been extracted from Active Record as activerecord-session_store gem. Please read the README.md file on the gem for the usage Fix reset_counters when there are multiple belongs_to association with the same foreign key and one of them have a counter cache Raise ArgumentError if list of attributes to change is empty in update_all Add Relation#load. This method explicitly loads the records and then returns self Deprecated most of the 'dynamic finder' methods. All dynamic methods except for find_by_... and find_by_...! are deprecated Added ability to ActiveRecord::Relation#from to accept other ActiveRecord::Relation objects Remove IdentityMap ActiveSupport changes excerpt ERB::Util.html_escape now escapes single quotes ActiveSupport::Callbacks: deprecate monkey patch of object callbacks Replace deprecated memcache-client gem with dalli in ActiveSupport::Cache::MemCacheStore Object#try will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the new Object#try! Object#try can't call private methods Add ActiveSupport::Deprecations.behavior = :silence to completely ignore Rails runtime deprecations What are the most important changes for you?

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• How a database is loaded into an application?

  - by Audel

  Hi All i need is a simple explanation on how does this function work I also attached a piece of php which I think is the one that retrieves the data from the database. Please correct me if I'm wrong Cheers. function loadDatabaseRecords () { // Mozilla/Safari if (window.XMLHttpRequest) { xmlHttpReq = new XMLHttpRequest(); } // IE else if (window.ActiveXObject) { xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP"); } alert ("To Server (Load Records):\n\najax-open-DB.php"); xmlHttpReq.open('GET', "ajax-open-DB.php", true); xmlHttpReq.onreadystatechange = loadDatabaseRecordsCallback; xmlHttpReq.send(null); } <?php $link = mysql_connect ("ipaddress", "localhost", "password"); mysql_select_db ("database1"); $query = "SELECT * from addressbook"; $result = mysql_query ($query); print "<table>"; print "<tr>"; print "<th>Firstname</th><th>Lastname</th><th>Address</th><th>Telephone</th>"; print "</tr>"; for ($i = 0; $i < mysql_num_rows ($result); $i ++) { $row = mysql_fetch_object ($result); print "<tr>"; print "<td>$row->firstname</td>"; print "<td>$row->lastname</td>"; print "<td>$row->address</td>"; print "<td>$row->telephone</td>"; print "</tr>"; } print "</table>"; mysql_close ($link); ?>

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• How do I add a filter button to this pagination?

  - by ClarkSKent

  Hey, I want to add a button(link), that when clicked will filter the pagination results. I'm new to php (and programming in general) and would like to add a button like 'Automotive' and when clicked it updates the 2 mysql queries in my pagination script, seen here: As you can see, the category automotive is hardcoded in, I want it to be dynamic, so when a link is clicked it places whatever the id or class is in the category part of the query. 1: $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); 2: $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); This is the entire current php pagination script that I am using: <?php //connecting to the database $error = "Could not connect to the database"; mysql_connect('localhost','root','root') or die($error); mysql_select_db('ajax_demo') or die($error); //max displayed per page $per_page = 2; //get start variable $start = $_GET['start']; //count records $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); //count max pages $max_pages = $record_count / $per_page; //may come out as decimal if (!$start) $start = 0; //display data $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); while ($row = mysql_fetch_assoc($get)) { // get data $name = $row['id']; $age = $row['site_name']; echo $name." (".$age.")<br />"; } //setup prev and next variables $prev = $start - $per_page; $next = $start + $per_page; //show prev button if (!($start<=0)) echo "<a href='pagi_test.php?start=$prev'>Prev</a> "; //show page numbers //set variable for first page $i=1; for ($x=0;$x<$record_count;$x=$x+$per_page) { if ($start!=$x) echo " <a href='pagi_test.php?start=$x'>$i</a> "; else echo " <a href='pagi_test.php?start=$x'><b>$i</b></a> "; $i++; } //show next button if (!($start>=$record_count-$per_page)) echo " <a href='pagi_test.php?start=$next'>Next</a>"; ?>

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• Does my TPL partitioner cause a deadlock?

  - by Scott Chamberlain

  I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the .Net example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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• Optimize slow ranking query

  - by Juan Pablo Califano

  I need to optimize a query for a ranking that is taking forever (the query itself works, but I know it's awful and I've just tried it with a good number of records and it gives a timeout). I'll briefly explain the model. I have 3 tables: player, team and player_team. I have players, that can belong to a team. Obvious as it sounds, players are stored in the player table and teams in team. In my app, each player can switch teams at any time, and a log has to be mantained. However, a player is considered to belong to only one team at a given time. The current team of a player is the last one he's joined. The structure of player and team is not relevant, I think. I have an id column PK in each. In player_team I have: id (PK) player_id (FK -> player.id) team_id (FK -> team.id) Now, each team is assigned a point for each player that has joined. So, now, I want to get a ranking of the first N teams with the biggest number of players. My first idea was to get first the current players from player_team (that is one record top for each player; this record must be the player's current team). I failed to find a simple way to do it (tried GROUP BY player_team.player_id HAVING player_team.id = MAX(player_team.id), but that didn't cut it. I tried a number of querys that didn't work, but managed to get this working. SELECT COUNT(*) AS total, pt.team_id, p.facebook_uid AS owner_uid, t.color FROM player_team pt JOIN player p ON (p.id = pt.player_id) JOIN team t ON (t.id = pt.team_id) WHERE pt.id IN ( SELECT max(J.id) FROM player_team J GROUP BY J.player_id ) GROUP BY pt.team_id ORDER BY total DESC LIMIT 50 As I said, it works but looks very bad and performs worse, so I'm sure there must be a better way to go. Anyone has any ideas for optimizing this? I'm using mysql, by the way. Thanks in advance Adding the explain. (Sorry, not sure how to format it properly) id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t ALL PRIMARY NULL NULL NULL 5000 Using temporary; Using filesort 1 PRIMARY pt ref FKplayer_pt77082,FKplayer_pt265938,new_index FKplayer_pt77082 4 t.id 30 Using where 1 PRIMARY p eq_ref PRIMARY PRIMARY 4 pt.player_id 1 2 DEPENDENT SUBQUERY J index NULL new_index 8 NULL 150000 Using index

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• Database schema for simple stats project

  - by Bubnoff

  Backdrop: I have a file hierarchy of cvs files for multiple locations named by dates they cover ...by month specifically. Each cvs file in the folder is named after the location. eg', folder name: 2010-feb contains: location1.csv location2.csv Each CSV file holds records like this: 2010-06-28, 20:30:00 , 0 2010-06-29, 08:30:00 , 0 2010-06-29, 09:30:00 , 0 2010-06-29, 10:30:00 , 0 2010-06-29, 11:30:00 , 0 meaning of record columns ( column names ): Date, time, # of sessions I have a perl script that pulls the data from this mess and originally I was going to store it as json files, but am thinking a database might be more appropriate long term ...comparing year to year trends ...fun stuff like that. Pt 2 - My question/problem: So I now have a REST service that coughs up json with a test database. My question is [ I suck at db design ], how best to design a database backend for this? I am thinking the following tables would suffice and keep it simple: Location: (PK)location_code, name session: (PK)id, (FK)location_code, month, hour, num_sessions I need to be able to average sessions (plus min and max) for each hour across days of week in addition to days of week in a given month or months. I've been using perl hashes to do this and am trying to decide how best to implement this with a database. Do you think stored procedures should be used? As to the database, depending on info gathered here, it will be postgresql or sqlite. If there is no compelling reason for postgresql I'll stick with sqlite. How and where should I compare the data to hours of operation. I am storing the hours of operation in a yaml file. I currently 'match' the hour in the data to a hash from the yaml to do this. Would a database open simpler methods? I am thinking I would do this comparison as I do now then insert the data. Can be recalled with: SELECT hour, num_sessions FROM session WHERE location_code=LOC1 Since only hours of operation are present, I do not need to worry about it. Should I calculate all results as I do now then store as a stats table for different 'reports'? This, rather than processing on demand? How would this look? Anyway ...I ramble. Thanks for reading! Bubnoff

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• Not allowing characters after Space. Mysql Insert With PHP

  - by Jake

  Ok so I think this is easy but I dont know (I'm a novice to PHP and MySQL). I have a select that is getting data from a table in the database. I am simply taking whatever options the user selects and putting it into a separate table with a php mysql insert statement. But I am having a problem. When I hit submit, everything is submitted properly except for any select options that have spaces don't submit after the first space. For example if the option was COMPUTER REPAIR, all that would get sent is COMPUTER. I will post code if needed, and any help would be greatly appreciated. Thanks! Ok here is my select code: <?php include("./config.php"); $query="SELECT id,name FROM category_names ORDER BY name"; $result = mysql_query ($query); echo"<div style='overflow:auto;width:100%'><label>Categories (Pick three that describe your business)</label><br/><select name='select1'><option value='0'>Please Select A Category</option>"; // printing the list box select command while($catinfo=mysql_fetch_array($result)){//Array or records stored in $nt echo "<option>$catinfo[name]</option><br/> "; } echo"</select></div>"; ?> And here is my insert code ( Just to let you know its got everything not just the select!) ?php require("./config.php"); $companyname = mysql_real_escape_string(addslashes(trim($_REQUEST['name']))); $phone = mysql_real_escape_string(addslashes($_REQUEST['phone'])); $zipcode = mysql_real_escape_string(addslashes($_REQUEST['zipcode'])); $city = mysql_real_escape_string(addslashes($_REQUEST['city'])); $description = mysql_real_escape_string(addslashes($_REQUEST['description'])); $website = mysql_real_escape_string(addslashes($_REQUEST['website'])); $address = mysql_real_escape_string(addslashes($_REQUEST['address'])); $other = mysql_real_escape_string(addslashes($_REQUEST['other'])); $payment = mysql_real_escape_string(addslashes($_REQUEST['payment'])); $products = mysql_real_escape_string(addslashes($_REQUEST['products'])); $email = mysql_real_escape_string(addslashes($_REQUEST['email'])); $select1 = mysql_real_escape_string(addslashes($_REQUEST['select1'])); $select2 = mysql_real_escape_string(addslashes($_REQUEST['select2'])); $select3 = mysql_real_escape_string(addslashes($_REQUEST['select3'])); $save=$_POST['save']; if(!empty($save)){ $sql="INSERT INTO gj (name, phone, city, zipcode, description, dateadded, website, address1, other2, payment_options, Products, email,cat1,cat2,cat3) VALUES ('$companyname','$phone','$city','$zipcode','$description',curdate(),'$website','$address','$other','$payment','$products','$email','$select1','$select2','$select3')"; if (!mysql_query($sql,$link)) { die('Error: ' . mysql_error()); } echo "<br/><h2><font color='green' style='font-size:15px'>1 business added</font></h2>"; mysql_close($link); } ?>

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• SQL Native Client 10 Performance miserable (due to server-side cursors)

  - by namezero

  we have an application that uses ODBC via CDatabase/CRecordset in MFC (VS2010). We have two backends implemented. MSSQL and MySQL. Now, when we use MSSQL (with the Native Client 10.0), retrieving records with SELECT is dramatically slow via slow links (VPN, for example). The MySQL ODBC driver does not exhibit this nasty behavior. For example: CRecordset r(&m_db); r.Open(CRecordset::snapshot, L"SELECT a.something, b.sthelse FROM TableA AS a LEFT JOIN TableB AS b ON a.ID=b.Ref"); r.MoveFirst(); while(!r.IsEOF()) { // Retrieve CString strData; crs.GetFieldValue(L"a.something", strData); crs.MoveNext(); } Now, with the MySQL driver, everything runs as it should. The query is returned, and everything is lightning fast. However, with the MSSQL Native Client, things slow down, because on every MoveNext(), the driver communicates with the server. I think it is due to server-side cursors, but I didn't find a way to disable them. I have tried using: ::SQLSetConnectAttr(m_db.m_hdbc, SQL_ATTR_ODBC_CURSORS, SQL_CUR_USE_ODBC, SQL_IS_INTEGER); But this didn't help either. There are still long-running exec's to sp_cursorfetch() et al in SQL Profiler. I have also tried a small reference project with SQLAPI and bulk fetch, but that hangs in FetchNext() for a long time, too (even if there is only one record in the resultset). This however only happens on queries with LEFT JOINS, table-valued functions, etc. Note that the query doesn't take that long - executing the same SQL via SQL Studio over the same connection returns in a reasonable time. Question1: Is is possible to somehow get the native client to "cache" all results locally use local cursors in a similar fashion as the MySQL driver seems to do it? Maybe this is the wrong approach altogether, but I'm not sure how else to do this. All we want is to retrieve all data at once from a SELECT, then never talk the server again until the next query. We don't care about recordset updates, deletes, etc or any of that nonsense. We only want to retrieve data. We take that recordset, get all the data, and delete it. Question2: Is there a more efficient way to just retrieve data in MFC with ODBC?

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• How should I organize my C# classes? [closed]

  - by oscar.fimbres

  I'm creating an email generator system. I'm creating some clases and I'm trying to make things right. By the time, I have created 5 classes. Look at the class diagram: I'm going to explain you each one. Person. It's not a big deal. Just have two constructors: Person(fname, lname1, lname2) and Person(token, fname, lname1, lname2). Note that email property stays without value. StringGenerator. This is a static class and it has only a public function: Generate. The function receives a Person class and it will return a list of patterns for the email. MySql. It contains all the necessary to connect to a database. Database. This class inherits from MySql class. It has particular functions for the database. This gets all the registries from a table (function GetPeople) and return a List. Each person from the list contains all data except Email. Also it can add records (List but this must contains an available email). An available email is when an email doesn't have another person. For that reason, I have a method named ExistsEmail. Container. This is the class which is causing me some problems. It's like a temporary container. It supposed to have a people list from GetPeople (in Database class) and for each person it adds, it must generate a list of possible names (StringGenerator.Generate), then it selects one of the list and it must check out if exists in the database or in the same container. As I told above this is temporal, it may none of the possible emails is available. So the user can modify or enter a custom email available and update the list in this container. When all the email's people are available, it sends a list to add in the database, It must have a Flush method, to insert all the people in the database. I'm trying to design correct class. I need a little help to improve or edite the classes, because I want to separate the logic and visual, and learn of you. I hope you've been able to understand me. Any question or doubt, please let me know. Anyway, I attached the solution here to better understand it: http://www.megaupload.com/?d=D94FH8GZ

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• RIM blackberry Record 3GP video

  - by pankaj_shukla

  Hi All, I am writing an application that can record a 3GP video. I have tried both MMAPI and Invoke API. But have following issues. Using MMAPI: 1. When I record to stream, It records video in RIMM streaming format. when I try to play this video player gives error "Unsupported media format.". 2. When I record to a file. It will create a file of size 0. Using Invoke API: 1. In MMS mode it does not allow to record a video more than 30 seconds. 2. In Normal mode size of the file is very large. 3. Once I invoke camera application I do not have any control on application. Here is my source code: _player = javax.microedition.media.Manager .createPlayer("capture://video?encoding=video/3gpp&mode=mms"); // I have tried every encoding returns from System.getProperty("video.encodings") method _player.realize(); _videoControl = (VideoControl) _player.getControl("VideoControl"); _recordControl = (RecordControl) _player.getControl("RecordControl"); _volumeControl = (VolumeControl) _player.getControl("VolumeControl"); String videoPath = System.getProperty("fileconn.dir.videos"); if (videoPath == null) { videoPath = "file:///store/home/user/videos/"; } _recordControl.setRecordLocation(videoPath + "RecordedVideo.3gp"); _player.addPlayerListener(this); Field videoField = (Field) _videoControl.initDisplayMode( VideoControl.USE_GUI_PRIMITIVE, "net.rim.device.api.ui.Field"); _videoControl.setVisible(true); add(videoField); _player.start(); ON start menu item Selection: try { _recordControl.startRecord(); } catch (Exception e) { _player.close(); showAlert(e.getClass() + " " + e.getMessage()); } On stop menuItem selection: try { _recordControl.commit(); } catch (Exception e) { _player.close(); showAlert(e.getClass() + " " + e.getMessage()); } Please let me if I am doing something wrong. Thanks, Pankaj

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• MySQL Split Time Ranges into Smaller Chunks

  - by Neren

  Hello all, I've recently been tasked with finishing a PHP/MySQL web app when the developer quit last week. I'm no MySQL expert, so I apologize if this is an intensely simple question. I've searched SO for the better part of two days trying to find a relatively easy solution to my problem, which is as follows. Problem in a Nutshell: I have a MySQL table full of start and end datetime (GMT -5) & UNIX Timestamp values covering durations of irregular length and need to break/split/divide them into more-regular time chunks (5 minutes). I'm not after a count of row entries per time chunk/bucket/period, if that makes any sense. Data Example: started, ended, started_UNIX, ended_UNIX 2010-10-25 15:12:33, 2010-10-25 15:47:09, 1288033953, 1288036029 What I'm hoping to get: 2010-10-25 15:12:33, 2010-10-25 15:15:00, 1288033953, 1288037700 2010-10-25 15:15:00, 2010-10-25 15:20:00, 1288037700, 1288038000 2010-10-25 15:20:00, 2010-10-25 15:25:00, 1288038000, 1288038300 2010-10-25 15:25:00, 2010-10-25 15:30:00, 1288038300, 1288038600 2010-10-25 15:30:00, 2010-10-25 15:35:00, 1288038600, 1288038900 2010-10-25 15:35:00, 2010-10-25 15:40:00, 1288038900, 1288039200 2010-10-25 15:40:00, 2010-10-25 15:45:00, 1288039200, 1288039500 2010-10-25 15:45:00, 2010-10-25 15:47:09, 1288039500, 1288039629 If you're interested, here's the quick & dirty on the app and why I need the data: App overview: The application receives very simple POST requests generated by a basic sensor device when its input pins go to ground, which submits an INSERT query to the database where MySQL records a timestamp (as started). When the input pins return from a grounded state, the device submits a different POST request, which causes the PHP app to submit an UPDATE query, where a modification time timestamp is inserted (as ended). My employer recently changed the periodic reporting unit of measure from Seconds "On" Per Day to Seconds "On" Per 5 Minute Interval. I had formulated what I thought would be a workable solution, but when I looked at it on paper, it looked like Rube Goldberg's nightmare constructed in MySQL, so that was out. Any suggestions as to how to break these spans into 5 minute blocks? Keeping it all in MySQL would be my preference, though I'll take any suggestions. Thank you for any suggestions you may have. Again, I apologize if this is a no-brainer. If I ask any additional questions of the SO collective consciousness in the future, I'll try to word them a bit better. Any help will be happily welcomed. Thanks, Neren

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• How to reliably categorize HTTP sessions in proxy to corresponding browser' windows/tabs user is viewing?

  - by Jehonathan

  I was using the Fiddler core .Net library as a local proxy to record the user activity in web. However I ended up with a problem which seems dirty to solve. I have a web browser say Google Chrome, and the user opened like 10 different tabs each with different web URLs. The problem is that the proxy records all the HTTP session initiated by each pages separately, causing me to figure out using my intelligence the tab which the corresponding HTTP session belonged to. I understand that this is because of the stateless nature of HTTP protocol. However I am just wondering is there an easy way to do this? I ended up with below c# code for that in Fiddler. Still its not a reliable solution due to the heuristics. This is a modification of the sample project bundled with Fiddler core for .NET 4. Basically what it does is filtering HTTP sessions initiated in last few seconds to find the first request or switching to another page made by the same tab in browser. It almost works, but not seems to be a universal solution. Fiddler.FiddlerApplication.AfterSessionComplete += delegate(Fiddler.Session oS) { //exclude other HTTP methods if (oS.oRequest.headers.HTTPMethod == "GET" || oS.oRequest.headers.HTTPMethod == "POST") //exclude other HTTP Status codes if (oS.oResponse.headers.HTTPResponseStatus == "200 OK" || oS.oResponse.headers.HTTPResponseStatus == "304 Not Modified") { //exclude other MIME responses (allow only text/html) var accept = oS.oRequest.headers.FindAll("Accept"); if (accept != null) { if(accept.Count>0) if (accept[0].Value.Contains("text/html")) { //exclude AJAX if (!oS.oRequest.headers.Exists("X-Requested-With")) { //find the referer for this request var referer = oS.oRequest.headers.FindAll("Referer"); //if no referer then assume this as a new request and display the same if(referer!=null) { //if no referer then assume this as a new request and display the same if (referer.Count > 0) { //lock the sessions Monitor.Enter(oAllSessions); //filter further using the response if (oS.oResponse.MIMEType == string.Empty || oS.oResponse.MIMEType == "text/html") //get all previous sessions with the same process ID this session request if(oAllSessions.FindAll(a=>a.LocalProcessID == oS.LocalProcessID) //get all previous sessions within last second (assuming the new tab opened initiated multiple sessions other than parent) .FindAll(z => (z.Timers.ClientBeginRequest > oS.Timers.ClientBeginRequest.AddSeconds(-1))) //get all previous sessions that belongs to the same port of the current session .FindAll(b=>b.port == oS.port ).FindAll(c=>c.clientIP ==oS.clientIP) //get all previus sessions with the same referrer URL of the current session .FindAll(y => referer[0].Value.Equals(y.fullUrl)) //get all previous sessions with the same host name of the current session .FindAll(m=>m.hostname==oS.hostname).Count==0 ) //if count ==0 that means this is the parent request Console.WriteLine(oS.fullUrl); //unlock sessions Monitor.Exit(oAllSessions); } else Console.WriteLine(oS.fullUrl); } else Console.WriteLine(oS.fullUrl); Console.WriteLine(); } } } } };

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• Strange behavior: save video recorded within app?

  - by Josue Espinosa

  I allow the user to record a video within my app, then later play it again. When a user records a video, I save the URL of the video, then play the video later from the saved URL. I save the video both in the Photos app and in my app. If I delete the video within the photos app, it still plays. After about 7 days, the video gets deleted. I think I am saving in my tmp directory, but i'm not sure. Here is what I am doing: -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { NSString *mediaType = [info objectForKey: UIImagePickerControllerMediaType]; [self dismissViewControllerAnimated:YES completion:nil]; // Handle a movie capture if (CFStringCompare ((__bridge_retained CFStringRef) mediaType, kUTTypeMovie, 0) == kCFCompareEqualTo) { NSString *moviePath = [NSString stringWithFormat:@"%@",[[info objectForKey:UIImagePickerControllerMediaURL] path]]; NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL]; NSData *videoData = [NSData dataWithContentsOfURL:videoURL]; _justRecordedVideoURL = [NSString stringWithFormat:@"%@",videoURL]; AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; _managedObjectContext = [appDelegate managedObjectContext]; Video *video = [NSEntityDescription insertNewObjectForEntityForName:@"Video" inManagedObjectContext:_managedObjectContext]; [video setVideoData:videoData]; [video setVideoURL:[NSString stringWithFormat:@"%@",videoURL]]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; dateFormatter.dateStyle = NSDateFormatterLongStyle; [dateFormatter setDateStyle:NSDateFormatterLongStyle]; NSDate *date = [dateFormatter dateFromString:[dateFormatter stringFromDate:[NSDate date]]]; NSString *dateAdded = [dateFormatter stringFromDate:date]; [video setDate_recorded:dateAdded]; if(_currentAthlete != nil){ [video setWhosVideo:_currentAthlete]; } NSError *error = nil; if(![_managedObjectContext save:&error]){ //handle dat error } NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *tempPath = [documentsDirectory stringByAppendingFormat:@"/vid1.mp4"]; BOOL success = [videoData writeToFile:tempPath atomically:NO]; if(success == FALSE){ NSLog(@"Video was not successfully saved."); } if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(moviePath)) { UISaveVideoAtPathToSavedPhotosAlbum(moviePath, self, @selector(video:didFinishSavingWithError:contextInfo:), nil); } } } Am I saving it incorrectly? When I go to play the video, it works fine, after a couple days the video will play without audio, then eventually it will be gone. Any ideas why?

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• AJAX: Problems returning multiple variables

  - by fwaokda

  First off sorry if I'm missing something simple just started working with AJAX today. I have an issue where I'm trying to get information from my database, but different records have different amounts of values. For instance, each record has a "features" column. In the features column I store a string. (ex: Feature1~Feature2~Feature3~Feature4... ) When I'm building the object I take apart the string and store all the features into an array. Some objects can have 1 feature others can have up to whatever. So... how do I return this values back to my ajax function from my php page? Below is my ajax function that I was trying and I'll provide a link with my php file. [ next.php : http://pastebin.com/SY74jV7X ] $("a#next").click(function() { $.ajax({ type : 'POST', url : 'next.php', dataType : 'json', data : { nextID : $("a#next").attr("rel") }, success : function ( data ) { var lastID = $("a#next").attr("rel"); var originID = $("a#next").attr("rev"); if(lastID == 1) { lastID = originID; } else { lastID--; } $("img#spotlight").attr("src",data.spotlightimage); $("div#showcase h1").text(data.title); $("div#showcase h2").text(data.subtitle); $("div#showcase p").text(data.description); $("a#next").attr("rel", lastID); for(var i=0; i < data.size; i++) { $("ul#features").append("<li>").text(data.feature+i).append("</li>"); } /* for(var j=1; j < data.picsize; j++) { $("div.thumbnails ul").append("<li>").text(data.image+j).append("</li>"); } */ }, error : function ( XMLHttpRequest, textStatus, errorThrown) { $("div#showcase h1").text("An error has occured: " + errorThrown); } }); });

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• Multiple column subselect in mysql 5 (5.1.42)

  - by rubber boots

  This one seems to be a simple problem, but I can't make it work in a single select or nested select. Retrieve the authors and (if any) advisers of a paper (article) into one row. I order to explain the problem, here are the two data tables (pseudo) papers (id, title, c_year) persons (id, firstname, lastname) plus a link table w/one extra attribute (pseudo): paper_person_roles( paper_id person_id act_role ENUM ('AUTHOR', 'ADVISER') ) This is basically a list of written papers (table: papers) and a list of staff and/or students (table: persons) An article my have (1,N) authors. An article may have (0,N) advisers. A person can be in 'AUTHOR' or 'ADVISER' role (but not at the same time). The application eventually puts out table rows containing the following entries: TH: || Paper_ID | Author(s) | Title | Adviser(s) | TD: || 21334 |John Doe, Jeff Tucker|Why the moon looks yellow|Brown, Rayleigh| ... My first approach was like: select/extract a full list of articles into the application, eg.SELECT q.id, q.title FROM papers AS q ORDER BY q.c_year and save the results of the query into an array (in the application). After this step, loop over the array of the returned information and retrieve authors and advisers (if any), via prepared statement (? is the paper's id) from the link table like:APPLICATION_LOOP(paper_ids in array) SELECT p.lastname, p.firstname, r.act_role FROM persons AS p, paper_person_roles AS r WHERE p.id=r.person_id AND r.paper_id = ? # The application does further processing from here (pseudo): foreach record from resulting records if record.act_role eq 'AUTHOR' then join to author_column if record.act_role eq 'ADVISER' then join to avdiser_column end print id, author_column, title, adviser_column APPLICATION_LOOP This works so far and gives the desired output. Would it make sense to put the computation back into the DB? I'm not very proficient in nontrivial SQL and can't find a solution with a single (combined or nested) select call. I tried sth. like SELECT q.title (CONCAT_WS(' ', (SELECT p.firstname, p.lastname AS aunames FROM persons AS p, paper_person_roles AS r WHERE q.id=r.paper_id AND r.act_role='AUTHOR') ) ) AS aulist FROM papers AS q, persons AS p, paper_person_roles AS r in several variations, but no luck ... Maybe there is some chance? Thanks in advance r.b.

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• Converting this code from ASP to PHP

  - by jethomas

  I'll admit I'm a novice programmer and really the only experience I have is in classic ASP. I'm looking for a way to convert this asp code to PHP. For a customer who only has access to a linux box but also as a learning tool for me. Thanks in advance for the help: Recordset and Function: Function pd(n, totalDigits) if totalDigits > len(n) then pd = String(totalDigits-len(n),"0") & n else pd = n end if End Function 'declare the variables Dim Connection Dim Recordset Dim SQL Dim SQLDate SQLDate = Year(Date)& "-" & pd(Month(Date()),2)& "-" & pd(Day(Date()),2) 'declare the SQL statement that will query the database SQL = "SELECT * FROM tblXYZ WHERE element_8 = 2 AND element_9 > '" & SQLDate &"'" 'create an instance of the ADO connection and recordset objects Set Connection = Server.CreateObject("ADODB.Connection") Set Recordset = Server.CreateObject("ADODB.Recordset") 'open the connection to the database Connection.Open "PROVIDER=MSDASQL;DRIVER={MySQL ODBC 5.1 Driver};SERVER=localhost;UID=xxxxx;PWD=xxxxx;database=xxxxx;Option=3;" 'Open the recordset object executing the SQL statement and return records Recordset.Open SQL,Connection Display page/loop: Dim counter counter = 0 While Not Recordset.EOF counter = counter + 1 response.write("<div><td width='200' valign='top' align='center'><a href='" & Recordset("element_6") & "' style='text-decoration: none;'><div id='ad_header'>" & Recordset("element_3") & "</div><div id='store_name' valign='bottom'>" & Recordset("element_5") & "</div><img id='photo-small-img' src='http://xyz.com/files/" & Recordset("element_7") & "' /><br /><div id='ad_details'>"& Recordset("element_4") & "</div></a></td></div>") Recordset.MoveNext If counter = 3 Then Response.Write("</tr><tr>") counter = 0 End If Wend

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• Webservice for uploading data: security considerations

  - by Philip Daubmeier

  Hi everyone! Im not sure about what authentification method I should use for my webservice. I've searched on SO, and found nothing that helped me. Preliminary Im building an application that uploads data from a local database to a server (running my webservice), where all records are merged and stored in a central database. I am currently binary serializing a DataTable, that holds a small fragment of the local database, where all uninteresting stuff is already filtered out. The byte[] (serialized DataTable), together with the userid and a hash of the users password is then uploaded to the webservice via SOAP. The application together with the webservice already work exactly like intended. The Problem The issue I am thinking about is now: What is if someone just sniffs the network traffic, 'steals' the users id and password hash to send his own SOAP message with modified data that corrupts my database? Options The approaches to solving that problem, I already thought of, are: Using ssl + certificates for establishing the connection: I dont really want to use ssl, I would prefer a simpler solution. After all, every information that is transfered to the webservice can be seen on the website later on. What I want to say is: there is no secret/financial/business-critical information, that has to be hidden. I think ssl would be sort of an overkill for that task. Encrypting the byte[]: I think that would be a performance killer, considering that the goal of the excercise was simply to authenticate the user. Hashing the users password together with the data: I kind of like the idea: Creating a checksum from the data, concatenating that checksum with the password-hash and hashing this whole thing again. That would assure the data was sent from this specific user, and the data wasnt modified. The actual question So, what do you think is the best approach in terms of meeting the following requirements? Rather simple solution (As it doesnt have to be super secure; no secret/business-critical information transfered) Easily implementable retrospectively (Dont want to write it all again :) ) Doesnt impact to much on performance What do you think of my prefered solution, the last one in the list above? Is there any alternative solution I didnt mention, that would fit better? You dont have to answer every question in detail. Just push me in the right direction. I very much appreciate every well-grounded opinion. Thanks in advance!

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• Techniques for querying a set of object in-memory in a Java application

  - by Edd Grant

  Hi All, We have a system which performs a 'coarse search' by invoking an interface on another system which returns a set of Java objects. Once we have received the search results I need to be able to further filter the resulting Java objects based on certain criteria describing the state of the attributes (e.g. from the initial objects return all objects where x.y z && a.b == c). The criteria used to filter the set of objects each time is partially user configurable, by this I mean that users will be able to select the values and ranges to match on but the attributes they can pick from will be a fixed set. The data sets are likely to contain <= 10,000 objects for each search. The search will be executed manually by the application user base probably no more than 2000 times a day (approx). It's probably worth mentioning that all the objects in the result set are known domain object classes which have Hibernate and JPA annotations describing their structure and relationship. Off the top of my head I can think of 3 ways of doing this: For each search persist the initial result set objects in our database, then use Hibernate to re-query them using the finer grained criteria. Use an in-memory Database (such as hsqldb?) to query and refine the initial result set. Write some custom code which iterates the initial result set and pulls out the desired records. Option 1 seems to involve a lot of toing and froing across a network to a physical Database (Oracle 10g) which might result in a lot of network and disk activity. It would also require the results from each search to be isolated from other result sets to ensure that different searches don't interfere with each other. Option 2 seems like a good idea in principle as it would allow me to do the finer query in memory and would not require the persistence of result data which would only be discarded after the search was complete. Gut feeling is that this could be pretty performant too but might result in larger memory overheads (which is fine as we can be pretty flexible on the amount of memory our JVM gets). Option 3 could be very performant but is something I would like to avoid as any code we write would require such careful testing that the time taken to acheive something flexible and robust enough would probably be prohibitive. I don't have time to prototype all 3 ideas so I am looking for comments people may have on the 3 options above, plus any further ideas I have not considered, to help me decide which idea might be most suitable. I'm currently leaning toward option 2 (in memory database) so would be keen to hear from people with experience of querying POJOs in memory too. Hopefully I have described the situation in enough detail but don't hesitate to ask if any further information is required to better understand the scenario. Cheers, Edd

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