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Use .htaccess to limit access to file downloads

- by jimiyash

I have downloads for static files like product.exe. I want to limit access to these files with a .htaccess file so that only certain users can download it. I think this can be handled with mod_rewrite and I found this snippet online that blocks bad sites using the referrer. RewriteEngine on # Options +FollowSymlinks RewriteCond %{HTTP_REFERER} http://example.com/downloads/confirm/3811 [NC,OR] RewriteRule .* - [F] Source: http://www.javascriptkit.com/howto/htaccess14.shtml Instead of blocking based on referrer, I want to allow based on referrer. That way, the referrer can be a URL that cannot be accessed without first logging in. I am thinking about going this route and using the http referrer to give permission to the file. I know it may not be the best way to do it, and I guess the referrer can be spoofed, but it does not have to be THAT secure. I am also open to other ideas you may have to for limitting access. Please

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Codeigniter setting multiple where conditions, how to unset one

- by Dustin

I've got a script that is a notify_url from paypal that is supposed to update multiple tables in my database using the following code: //update first table $this-db-where('someid', $somid); $this-db-update('table', $data); ///update second table $this-db-where('somesecondid', $somesecondid) $this-db-update('anothertable', $data2); Then I get the following error: Unknown column 'somesecondid' in 'where clause' UPDATE anothertable SET avail = 0 WHERE someid = '13' AND somesecondid = '199' So codeigniter is combining those where clauses into a single query. Is there a way to unset the first one so it only has "UPDATE anothertable SET avail=0 WHERE somesecondid = 199" ? Thanks!

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LIMIT amount of rows fetched by JOIN

- by user892134

How do i LIMIT the child rows fetched to only 5? Here is the SQLfiddle http://sqlfiddle.com/#!2/bd96a/2. Right now it fetches all rows with parentid='4' and parentid='14'. It should only fetch 5 of each parentid. Assuming i have hundreds of rows, it should only fetch a max of 5 for each parentid. "SELECT child.* FROM mytable as parent LEFT JOIN mytable as child on child.parentid=parent.id WHERE parent.pageid IN ( 1, 2) AND parent.submittype='1' ORDER BY child.id ASC"; How do i solve this?

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Limit text area value and cut the rest

- by streetparade

I have a textarea which users can enter some tags. I need to limit this tags to 20 tags. Tags could be enterer this way maytag1,mytag2,mytag3 What i wrote is this function function limitTags() { var tags = $("input[type=text][name=tags]").val() var tag = $.trim(tags); var selected = new Array(); /** * replace the last ',' */ if(tag.substring(tag.length - 1) == ",") { *///tag = tag.replace(tag.length - 1, ''); } var enteredTags = tag.split(","); if( enteredTags.length > 20 ) { //$("input[type=text][name=tags]").val(enteredTags.join(",", enteredTags)); alert("Only 20 Tags allowed"); } } The alert works just fine but, after the alert box is gone. i can continiue entering tags till the alert box appears. What i need is cut the text after the messagebox which was entered also the last "," I hope i could ask my question clear. Thanks

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Using Session to limit form submission by time

- by user1733850

I have spent over 2 hours scouring the net trying to figure this out. I am trying to stop multiple form submission any faster than 60 seconds. Here is what I am using. session_start(); if (!isset($_SESSION['last_submit'])) $_SESSION['last_submit'] = time(); if (time()-$_SESSION['last_submit'] < 60) die('Post limit exceeded. Please wait at least 60 seconds'); else $_SESION['last_submit'] = time(); I found this bit here on the site but haven't been able to figure anything else out as far as getting it to work. I have this bit of code on my page at the beginning that does the DB query with the previous pages POST results. Do I need to set $last_submit to a certain value? Any help is appreciated.

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Limit output of all Linux commands

- by daniel

I'm looking for a way to limit the amount of output produced by all command line programs in Linux, and preferably tell me when it is limited. I'm working over a server which has a lag on the display. Occasionally I will accidentally run a command which outputs a large amount of text to the terminal, such as cat on a large file or ls on a directory with many files. I then have to wait a while for all the output to be printed to the terminal. So is there a way to automatically pipe all output into a command like head or wc to prevent too much output having to be printed to terminal?

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Using javascript to limit survey choices to three unique values

- by leanne

I'm required to use a limited survey application, and have to adapt the provided code to meet more advanced functionality. I need to create a weighted ranking question, so users can select their top three choices and the data will go into the survey application and be accessible in the survey reports. The application only supports 2 types of questions (text fill & multiple choice) but I can alter the code, as long as it still sends the form data back to the survey application. The code is set up so it will show a drop-down menu of 0-3 for each option. Now I want to limit the user's choices so they can only select one "1" "2" or "3", three choices total. Ideally, if the user already had "2" selected for one option and they tried to select it for another option, it would set the first "2" as "0" or blank. Is this possible to do with javascript? If so, does anyone know of a site that might show code like this, or provide similar enough examples that I could adapt it? Current code here: <html> <head><title>Survey</title></head>  <link href="---" rel="stylesheet" type="text/css"> <body bgcolor="#3c76a3">  <table border="0" align="center" cellpadding="0" cellspacing="0" style="background-attachment: scroll; background-color: #3c76a3; background-repeat: no-repeat; background-position: left top;" bgcolor="#3c76a3" topmargin="0" marginwidth="0" marginheight="0" width="100%" height="100%"> <tr> <td> <table border="0" align="center" cellpadding="0" cellspacing="0" id="survey"> <tr> <td><p> </p>  <form name="survey" action="---" method="POST"> <FONT face="Verdana, Arial, Helvetica, sans-serif"> <b>survey</b><hr>  <input type=hidden name="Buy R.J. a DeLorean_multiple_answers" value="one"> <font size=2><select name="Buy R.J. a DeLorean" SIZE=1> <option value=""> <option value="0">0 <option value="1">1 <option value="2">2 <option value="3">3 </select></font> <input type="hidden" name="Buy R.J. a DeLorean_help" value=""> <b><font size=2>Buy R.J. a DeLorean</font></b> <hr size=1>  <input type=hidden name="Fill Lisa's office with marshmallows._multiple_answers" value="one"> <font size=2><select name="Fill Lisa's office with marshmallows." SIZE=1> <option value=""> <option value="0">0 <option value="1">1 <option value="2">2 <option value="3">3 </select></font> <input type="hidden" name="Fill Lisa's office with marshmallows._help" value=""> <b><font size=2>Fill Lisa's office with marshmallows.</font></b> <hr size=1>  <input type=hidden name="Install a beer fridge in everyone's filing cabinets._multiple_answers" value="one"> <font size=2><select name="Install a beer fridge in everyone's filing cabinets." SIZE=1> <option value=""> <option value="0">0 <option value="1">1 <option value="2">2 <option value="3">3 </select></font> <input type="hidden" name="Install a beer fridge in everyone's filing cabinets._help" value=""> <b><font size=2>Install a beer fridge in everyone's filing cabinets.</font></b> <hr size=1>  <input type=hidden name="Buy a company Cessna_multiple_answers" value="one"> <font size=2><select name="Buy a company Cessna" SIZE=1> <option value=""> <option value="0">0 <option value="1">1 <option value="2">2 <option value="3">3 </select></font> <input type="hidden" name="Buy a company Cessna_help" value=""> <b><font size=2>Buy a company Cessna</font></b><br> <hr size=1>  <input type=hidden name="Replace Conf2's chairs with miniature ponies._multiple_answers" value="one"> <font size=2><select name="Replace Conf2's chairs with miniature ponies." SIZE=1> <option value=""> <option value="0">0 <option value="1">1 <option value="2">2 <option value="3">3 </select></font> <input type="hidden" name="Replace Conf2's chairs with miniature ponies._help" value=""> <b><font size=2>Replace Conf2's chairs with miniature ponies.</font></b> <hr size=1> <input type="hidden" name="question_names" value="{Buy R.J. a DeLorean} {Fill Lisa's office with marshmallows.} {Install a beer fridge in everyone's filing cabinets.} {Buy a company Cessna} {Replace Conf2's chairs with miniature ponies.}"> <p align="right"><input type="image" BORDER=0 title="Save Changes" alt="Save Changes" src="---" name="button_save_changes"> <input type="hidden" name="showconfirm" value="T"> <input type="hidden" name="showresults" value="F"> <input type="hidden" name="preventdupesmemberid" value="T"> <input type="hidden" name="preventdupesip" value="F"> <input type="hidden" name="numberquestions" value="F"> <input type="hidden" name="destinationurl" value=""> <input type="hidden" name="original_survey_id" value="62"> </form>  </td> </tr> </table> </td> </tr> </table>  </body> </html>

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AT&T U-verse 2Wire Router - Increase session table limit?

- by caleban

AT&T U-verse VDSL "fiber to the node" 24Mbit down / 3Mbit up 2Wire Router Model 3800HGV-B Software Version 6.1.9.24-enh.tm The 2Wire router appears to have a limit of 1024 TCP and UDP sessions. This limit appears to apply to all sessions regardless of any static IP, firewall off, DMZ plus, secondary router configurations. I've tried using the 2Wire router alone and also configuring the 2Wire static IP addressing, firewall off, DMZ plus, etc. setup along with my own pfSense router/firewall. Either way it appears I exceed the 1024 session limit and sessions start being reset. Running out of sessions isn't being caused by torrents or p2p etc. We're a business and our legitimate uses are exceeding this session limit. AT&T tells me it's not possible to bridge the router or increase or avoid the session table limit. I'm curious if anyone has found a way around either of these issues.

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Duration of Excessive GC Time in "java.lang.OutOfMemoryError: GC overhead limit exceeded"

- by jilles de wit

Occasionally, somewhere between once every 2 days to once every 2 weeks, my application crashes in a seemingly random location in the code with: java.lang.OutOfMemoryError: GC overhead limit exceeded. If I google this error I come to this SO question and that lead me to this piece of sun documentation which expains: The parallel collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small. If necessary, this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line. Which tells me that my application is apparently spending 98% of the total time in garbage collection to recover only 2% of the heap. But 98% of what time? 98% of the entire two weeks the application has been running? 98% of the last millisecond? I'm trying to determine a best approach to actually solving this issue rather than just using -XX:-UseGCOverheadLimit but I feel a need to better understand the issue I'm solving.

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sql query - how to apply limit within group by

- by Raj

hey guys assuming i have a table named t1 with following fields: ROWID, CID, PID, Score, SortKey it has the following data: 1, C1, P1, 10, 1 2, C1, P2, 20, 2 3, C1, P3, 30, 3 4, C2, P4, 20, 3 5, C2, P5, 30, 2 6, C3, P6, 10, 1 7, C3, P7, 20, 2 what query do i write so that it applies group by on CID, but instead of returning me 1 single result per group, it returns me a max of 2 results per group. also where condition is score = 20 and i want the results ordered by CID and SortKey. If I had to run my query on above data, i would expect the following result: RESULTS FOR C1 - note: ROWID 1 is not considered as its score < 20 C1, P2, 20, 2 C1, P3, 30, 3 RESULTS FOR C2 - note: ROWID 5 appears before ROWID 4 as ROWID 5 has lesser value SortKey C2, P5, 30, 2 C2, P4, 20, 3 RESULTS FOR C3 - note: ROWID 6 does not appear as its score is less than 20 so only 1 record returned here C3, P7, 20, 2 IN SHORT, I WANT A LIMIT WITHIN A GROUP BY. I want the simplest solution and want to avoid temp tables. sub queries are fine. also note i am using sqlite for this

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Subclassing NSArrayController in order to limit size of arrangedObjects

- by Simone Manganelli

I'm trying to limit the number of objects in an array controller, but I still want to be able to access the full array, if necessary. A simple solution I came up with was to subclass NSArrayController, and define a new method named "limitedArrangedObjects", that returns a limited number of objects from the real set of arranged objects. (I've seen http://stackoverflow.com/questions/694493/limiting-the-number-of-objects-in-nsarraycontroller , but that doesn't address my problem.) I want this property to be observable via bindings, so I set a dependency to arrangedObjects on it. Problem is, when arrangedObjects is updated, limitedArrangedObjects seems not to be observing the value change in arrangedObjects. I've hooked up an NSCollectionView to limitedArrangedObjects, and zero objects are being displayed. (If I bind it to arrangedObjects instead, all the objects show up as expected.) What's the problem? Here's the relevant code: @property (readonly) NSArray *limitedArrangedObjects; - (NSArray *)limitedArrangedObjects; { NSArray *arrangedObjects = [super arrangedObjects]; NSUInteger upperLimit = 10000; NSUInteger count = [arrangedObjects count]; if (count > upperLimit) count = upperLimit; arrayToReturn = [arrangedObjects subarrayWithRange:NSMakeRange(0, count)]; return arrayToReturn; } + (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key; { NSSet *keyPaths = [super keyPathsForValuesAffectingValueForKey:key]; if ([key isEqualToString:@"limitedArrangedObjects"]) { NSSet *affectingKeys = [NSSet setWithObjects:@"arrangedObjects",nil]; keyPaths = [keyPaths setByAddingObjectsFromSet:affectingKeys]; } return keyPaths; }

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Truncate portions of a string to limit the whole string's length in Ruby

- by Horace Loeb

Suppose you want to generate dynamic page titles that look like this: "It was all a dream, I used to read word up magazine" from "Juicy" by The Notorious B.I.G I.e., "LYRICS" from "SONG_NAME" by ARTIST However, your title can only be 69 characters total and this template will sometimes generate titles that are longer. One strategy for solving this problem is to truncate the entire string to 69 characters. However, a better approach is to truncate the less important parts of the string first. I.e., your algorithm might look something like this: Truncate the lyrics until the entire string is <= 69 characters If you still need to truncate, truncate the artist name until the entire string is <= 69 characters If you still need to truncate, truncate the song name until the entire string is <= 69 characters If all else fails, truncate the entire string to 69 characters Ideally the algorithm would also limit the amount each part of the string could be truncated. E.g., step 1 would really be "Truncate the lyrics to a minimum of 10 characters until the entire string is <= 69 characters" Since this is such a common situation, I was wondering if someone has a library or code snippet that can take care of it.

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How to Avoid PHP Object Nesting/Creation Limit?

- by Will Shaver

I've got a handmade ORM in PHP that seems to be bumping up against an object limit and causing php to crash. Here's a simple script that will cause crashes: <? class Bob { protected $parent; public function Bob($parent) { $this->parent = $parent; } public function __toString() { if($this->parent) return (string) "x " . $this->parent; return "top"; } } $bobs = array(); for($i = 1; $i < 40000; $i++) { $bobs[] = new Bob($bobs[$1 -1]); } ?> Even running this from the command line will cause issues. Some boxes take more than 40,000 objects. I've tried it on Linux/Appache (fail) but my app runs on IIS/FastCGI. On FastCGI this causes the famous "The FastCGI process exited unexpectedly" error. Obviously 20k objects is a bit high, but it crashes with far fewer objects if they have data and nested complexity. Fast CGI isn't the issue - I've tried running it from the command line. I've tried setting the memory to something really high - 6,000MB and to something really low - 24MB. If I set it low enough I'll get the "allocated memory size xxx bytes exhausted" error. I'm thinking that it has to do with the number of functions that are called - some kind of nesting prevention. I didn't think that my ORM's nesting was that complicated but perhaps it is. I've got some pretty clear cases where if I load just ONE more object it dies, but loads in under 3 seconds if it works.

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Rate Limit Calls To Api Using Cache

- by namtax

Hi I am using coldfusion to call the last.fm api, using a cfc bundle sourced from here I am concerned about going over the request limit, which is 5 requests per originating IP address per second, averaged over a 5 minute period. The cfc bundle has a central component which calls all the other components, which are split up into sections like "artist", "track" etc...This central component "lastFmApi.cfc." is initiated in my application, and persisted for the lifespan of the application // Application.cfc example <cffunction name="onApplicationStart"> <cfset var apiKey = '[your api key here]' /> <cfset var apiSecret = '[your api secret here]' /> <cfset application.lastFm = CreateObject('component', 'org.FrankFusion.lastFm.lastFmApi').init(apiKey, apiSecret) /> </cffunction> Now if I want to call the api through a handler/controller, for example my artist handler...I can do this <cffunction name="artistPage" cache="5 mins"> <cfset qAlbums = application.lastFm.user.getArtist(url.artistName) /> </cffunction> I am a bit confused towards caching, but am caching each call to the api in this handler for 5 mins, but does this make any difference, because each time someone hits a new artist page wont this still count as a fresh hit against the api? Wondering how best to tackle this Thanks

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Copy recordset data into multiple sheets to avoid problem of maximum rows limit in Excel VBA

- by Sam

I am developing reporting application in Excel/vba 2003. VBA code sends search query to database and gets the data through recordset. It will then be copied to one of excel sheet. The rertrieved data looks like as shown below. ProductID--|---DateProcessed--|----State----- 1................|.. 1/1/2010..............|.....Picked Up 1................|.. 1/1/2010..............|.....Forward To Approver 1................|.. 1/2/2010..............|.....Approver Picked Up 1................|.. 1/3/2010..............|.....Approval Completed 2................|.. 1/1/2010..............|.....Picked Up 3................|.. 1/2/2010..............|.....Picked Up 3................|.. 1/2/2010..............|.....Forward To Approver The problem is data retrieved from search query is so huge that it goes above the excel row limit (65536 rows in excel 2003). So I want to split this data into two excel sheets. While spliting the data I want to ensure that the data for same product shoud remain in one sheet. For example, if the last record in the above result set is 65537th record then I also want to move all records for product 3 into new sheet. So sheet1 will contain records for product id 1 and 2 with total records = 65534. Sheet 2 will cotain records for product id 3 - with total records = 2. How can I acheive this in vba? If it is not possible, is there any alternative solution ? Thanks in Advance !

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Limit CPU usage of a process

- by jb

I have a service running which periodically checks a folder for a file and then processes it. (Reads it, extracts the data, stores it in sql) So I ran it on a test box and it took a little longer thaan expected. The file had 1.6 million rows, and it was still running after 6 hours (then I went home). The problem is the box it is running on is now absolutely crippled - remote desktop was timing out so I cant even get on it to stop the process, or attach a debugger to see how far through etc. It's solidly using 90%+ CPU, and all other running services or apps are suffering. The code is (from memory, may not compile): List<ItemDTO> items = new List<ItemDTO>(); using (StreamReader sr = fileInfo.OpenText()) { while (!sr.EndOfFile) { string line = sr.ReadLine() try { string s = line.Substring(0,8); double y = Double.Parse(line.Substring(8,7)); //If the item isnt already in the collection, add it. if (items.Find(delegate(ItemDTO i) { return (i.Item == s); }) == null) items.Add(new ItemDTO(s,y)); } catch { /*Crash*/ } } return items; } - So I am working on improving the code (any tips appreciated). But it still could be a slow affair, which is fine, I've no problems with it taking a long time as long as its not killing my server. So what I want from you fine people is: 1) Is my code hideously un-optimized? 2) Can I limit the amount of CPU my code block may use? Cheers all

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How to limit TCP writes to particular size and then block untlil the data is read

- by ustulation

{Qt 4.7.0 , VS 2010} I have a Server written in Qt and a 3rd party client executable. Qt based server uses QTcpServer and QTcpSocket facilities (non-blocking). Going through the articles on TCP I understand the following: the original implementation of TCP mentioned the negotiable window size to be a 16-bit value, thus maximum being 65535 bytes. But implementations often used the RFC window-scale-extension that allows the sliding window size to be scalable by bit-shifting to yield a maximum of 1 gigabyte. This is implementation defined. This could have resulted in majorly different window sizes on receiver and sender end as the server uses Qt facilities without hardcoding any window size limit. Client 1st asks for all information it can based on the previous messages from the server before handling the new (accumulating) incoming messages. So at some point Server receives a lot of messages each asking for data of several MB's. This the server processes and puts it into the sender buffer. Client however is unable to handle the messages at the same pace and it seems that client’s receiver buffer is far smaller (65535 bytes maybe) than sender’s transmit window size. The messages thus get accumulated at sender’s end until the sender’s buffer is full too after which the TCP writes on sender would block. This however does not happen as sender buffer is much larger. Hence this manifests as increase in memory consumption on the sender’s end. To prevent this from happening, I used Qt’s socket’s waitForBytesWritten() with timeout set to -1 for infinite waiting period. This as I see from the behaviour blocks the thread writing TCP data until the data has actually been sensed by the receiver’s window (which will happen when earlier messages have been processed by the client at application level). This has caused memory consumption at Server end to be almost negligible. is there a better alternative to this (in Qt) if i want to restrict the memory consumption at server end to say x MB's? Also please point out if any of my understandings is incorrect.

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python recursive iteration exceeding limit for tree implementation

- by user3698027

I'm implementing a tree dynamically in python. I have defined a class like this... class nodeobject(): def __init__(self,presentnode=None,parent=None): self.currentNode = presentnode self.parentNode = parent self.childs = [] I have a function which gets possible childs for every node from a pool def findchildren(node, childs): # No need to write the whole function on how it gets childs Now I have a recursive function that starts with the head node (no parent) and moves down the chain recursively for every node (base case being the last node having no children) def tree(dad,children): for child in children: childobject = nodeobject(child,dad) dad.childs.append(childobject) newchilds = findchildren(child, children) if len(newchilds) == 0: lastchild = nodeobject(newchilds,childobject) childobject.childs.append(lastchild) loopchild = copy.deepcopy(lastchild) while loopchild.parentNode != None: print "last child" else: tree(childobject,newchilds) The tree formation works for certain number of inputs only. Once the pool gets bigger, it results into "MAXIMUM RECURSION DEPTH EXCEEDED" I have tried setting the recursion limit with set.recursionlimit() and it doesn't work. THe program crashes. I want to implement a stack for recursion, can someone please help, I have gone no where even after trying for a long time ?? Also, is there any other way to fix this other than stack ?

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Nested IF statements in Excel [Over the 7 allowed limit]

- by Alks

hey guys, i am trying to create a spreadsheet which automagically gives a grade to a student based on their marks they got. I've apparently hit excels nested IF statement limit which is 7. here's my if statement: =IF(O5>0.895,"A+",IF(O5>0.845,"A",IF(O5>0.795,"A-",IF(O5>0.745,"B+",IF(O5>0.695,"B",IF(O5>0.645,"B-",IF(O5>0.595,"C+",IF(O5>0.545,"C","D")))))))) I was reading online that I could create a VBA script and assign it that, but I dont know anything about VBA....so if someone could help me write a VBA for this, would be awesome. Its still mising the C- grade and anything lower should be awarded a D mark. This is the grading scheme I am trying to create...: A+ 89.500 - 100.000 Pass with Distinction A 84.500 - 89.490 Pass with Distinction A- 79.500 - 84.490 Pass with Distinction B+ 74.500 - 79.490 Pass with Merit B 69.500 - 74.490 Pass with Merit B- 64.500 - 69.490 Pass with Merit C+ 59.500 - 64.490 Pass C 54.500 - 59.490 Pass C- 49.500 - 54.490 Pass D 0.000 - 49.490 Specified Fail I wouldn't mind going down the VBA route, however my understanding of VB language is absolutely minimal (don't like it)...if this gets too tedious, I was thinking to create a small php/mysql application instead. Cheers :)

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JPQL / SQL: How to select * from a table with group by on a single column?

- by DavidD

I would like to select every column of a table, but want to have distinct values on a single attribute of my rows (City in the example). I don't want extra columns like counts or anything, just a limited number of results, and it seems like it is not possible to directly LIMIT results in a JPQL query. Original table: ID | Name | City --------------------------- 1 | John | NY 2 | Maria | LA 3 | John | LA 4 | Albert | NY Wanted result, if I do the distinct on the City: ID | Name | City --------------------------- 1 | John | NY 2 | Maria | LA What is the best way to do that? Thank you for your help.

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PHP - Plesk - Cron - Allowed memory size exhausted?

- by John

ini_set('max_execution_time',0); ini_set('memory_limit','1000M'); These are the first two lines at the very top of my script. I was under the impression if I ran something via cron memory limits didn't apply, but I was wrong. Safe mode is off and when I test to see if these values are being set they are but I keep getting the good ol' "PHP Fatal: Memory exhausted" error. Any ideas what I may be doing wrong? And whats the "more elegant way" of writing "infinite" for the "memory limit" value is it -1 or something?

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Beginner SQL section: avoiding repeated expression

- by polygenelubricants

I'm entirely new at SQL, but let's say that on the StackExchange Data Explorer, I just want to list the top 15 users by reputation, and I wrote something like this: SELECT TOP 15 DisplayName, Id, Reputation, Reputation/1000 As RepInK FROM Users WHERE RepInK > 10 ORDER BY Reputation DESC Currently this gives an Error: Invalid column name 'RepInK', which makes sense, I think, because RepInK is not a column in Users. I can easily fix this by saying WHERE Reputation/1000 > 10, essentially repeating the formula. So the questions are: Can I actually use the RepInK "column" in the WHERE clause? Do I perhaps need to create a virtual table/view with this column, and then do a SELECT/WHERE query on it? Can I name an expression, e.g. Reputation/1000, so I only have to repeat the names in a few places instead of the formula? What do you call this? A substitution macro? A function? A stored procedure? Is there an SQL quicksheet, glossary of terms, language specification, anything I can use to quickly pick up the syntax and semantics of the language? I understand that there are different "flavors"?

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How can I implement a download rate limited in Java?

- by JohnWithoutArms

Hello, I'm going to implement a (simple) downloader application in Java as a personal exercise. It is going to run several jobs in different threads, in a way that I will be downloading a few files at the same time at all times during execution. I want to be able to define a download rate limit that is shared between all the download jobs, but I don't know how to do it even for a single download task. How should I go about doing this? What are the solutions I should try implementing? Thanks.

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MySQL: Return grouped fields where the group is not empty, effeciently

- by Ryan Badour

In one statement I'm trying to group rows of one table by joining to another table. I want to only get grouped rows where their grouped result is not empty. Ex. Items and Categories SELECT Category.id FROM Item, Category WHERE Category.id = Item.categoryId GROUP BY Category.id HAVING COUNT(Item.id) > 0 The above query gives me the results that I want but this is slow, since it has to count all the rows grouped by Category.id. What's a more effecient way? I was trying to do a Group By LIMIT to only retrieve one row per group. But my attempts failed horribly. Any idea how I can do this? Thanks

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MySQL: Return grouped fields where the group is not empty, efficiently

- by Ryan Badour

In one statement I'm trying to group rows of one table by joining to another table. I want to only get grouped rows where their grouped result is not empty. Ex. Items and Categories SELECT Category.id FROM Item, Category WHERE Category.id = Item.categoryId GROUP BY Category.id HAVING COUNT(Item.id) > 0 The above query gives me the results that I want but this is slow, since it has to count all the rows grouped by Category.id. What's a more effecient way? I was trying to do a Group By LIMIT to only retrieve one row per group. But my attempts failed horribly. Any idea how I can do this? Thanks

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