SQL - group by - merge a column's values into one row?
Simulating group_concat MySQL function in Microsoft SQL Server 2005?
How do I free up disk space? My Ubuntu cloud server has left only 900MB of disk space.   I'll just empty the directory /tmp and wondering if there is any other location to clean up. What's the best way to communicate between view controllers? I understand that the word “precious” in the following quote of Maureen Dowd’s article “Heart of Darkness” (NYT, March 20) literally means “2. valuable or important and not to be wasted” as defined in OALD:     Congressman Jones read an e-mail from a former boss of General   Allen’s, giving the congressman this unvarnished assessment:   “Attempting to find a true military and political answer to the   problems in Afghanistan would take decades. Would drain our nation of   precious resources, with the most precious being our sons and daughters. Simply put, the United States cannot solve the Afghan   problem, no matter how brave and determined our troops are.   But I didn’t know “precious” has another meaning as defined in OALD: 5. (disapproving, people and their behavior) very formal, exaggerated and not natural, and Readers English Dictionary: 2.(colloquial) terrible, almost worthless, until I was told by my respected forum mate a few days ago.   Being encouraged by his suggestion for me to “ask another question if I’m not sure of what he means by describing his input as “precious” is actually rather “precious” phrasing, I would like to ask:   What is an example of “precious” being used as “disapproving” or sarcastic way (as neither OALD nor CALD provides examples)? Is there an easy way to discern the instance “precious” being used as “disapproving” from the case being used in the sense of genuine “great value” as used in the above quote other than judging from the context? Possible Duplicate:    It's time once again to support your favorite open source project through our Free Vote-Based Advertising for Open Source Projects. We are clearing the leader boards to start the first half of 2011 anew. Here is your chance to create a . Create a graphical ad for an open source programming project and post it as an answer to this question (in the right format), and it will feed live remnant ads on Stack Overflow. Ad Requirements It must be an advertisement soliciting the participation and contribution of programmers writing actual source code. This is not intended as a general purpose ad for consumer products which just happen to be open source. It's for finding programmers who will help contribute code or other programmery things (documentation, code review, bug fixes, etc.). Your ad should be an original creation which has not previously appeared on Stack Overflow. Please do not resubmit entries that have appeared as ads on Stack Overflow in previous periods. In order to work, the answers you post to this question must conform to the following rules. Answer Template  [![Tagline to show on mouseover][1]][2]        [1]: http://image-url   [2]: http://clickthrough-url   Please do not add anything else to the body of the post. If you want to add any commentary, keep it in the comments. Image requirements  The image that you create must be 220 pixels by 250 pixels Can be hosted anywhere (tinypic, twitpic, your blog); we will mirror the image locally when we serve it. Must be GIF or PNG No animated GIFs Absolute limit on file size of 150 KB  The output, which ultimately will be served in an ad slot on Stack Overflow, can be previewed by clicking through to this URL:  Score Threshold There is a minimum score threshold an answer must meet (currently 6) before it will be served up by that URL and shown on Stack Overflow. You can see all the ads that currently make the threshold and meet our criteria on this page:  You can also view the ads that meet the threshold using 's C programming, why does this large array declaration produce a segmentation fault? Let $\mathbb S = \varnothing$.      Then from the definition: $ \bigcap \mathbb S = \left\{{x: \forall X \in \mathbb S: x \in X}\right\}$      Consider any $x \in \mathbb U$.      Then as $\mathbb S = \varnothing$, it follows that: $\forall X \in \mathbb S: x \in X$ from the definition of vacuous truth.      It follows directly that: $\bigcap \mathbb S = \left\{{x: x \in \mathbb U}\right\}$      That is: $\bigcap \mathbb S = \mathbb U$. ()   Proofwiki uses the above "proof" to "prove" that intersection of the empty set is the whole universe.   My question is, is the use of vacuous truth really allowed in axiomatic set theory, like ZFC? I don't see how the use of vacuous truth is justified.   The next problem I can think of is that we cannot really "define" the elements of empty set (to my knowledge, there is no element in empty set) so how can we then prove as the above proof did? This seems to contradict the use of vacuous truth.  And of course, there is issue of using the whole universe as a set, and I don't think this is allowed.... (Maybe proof above is using a different axiomatic set theory, as I am using ZF-minded thoughts...) Is there any general way to obtain the review ID or review summary for a certain review job without the 10 k tools? Accessing the full review history is a privilege for 10 k users but, statistics for individual reviews can be viewed by everybody ( ).  These review summaries can be somewhat useful for different aspects, such as understanding what happened to a review item that you initiated, e.g., if your close vote remained the only one on a question, you can only guess by the elapsed time whether nobody else has reviewed it or whether the review is finished with everybody disagreeing. Or you can see who performed a disputed review decision and discuss it.  My question now is: Is there any way to acess these review summaries or obtain the review ID – which would allow to find these summaries – for a particular review task?  I am aware that the above information, in particular the reviewer identity, can be abused and it may therefore be undesirable that everybody can find this information. But then, at least on small sites, it’s quite possible to obtain the review ID from guessing. Also, I can access the review summary for every review that I participated in or even skipped from my review history and the review summary for every successful edit from the edit history. How to enable virtualization on booting? (Ubuntu 13.10) I always thought with "any" I should use the plural, but on the internet I can find both:   It can be found in any book. It can be found in any books Do you have any books? It can be said in any language.  This can be understood by anyone.  It has been used in any form.   So, what's correct?  Is there any rule? I am a software engineer but try to keep up with maths as I really enjoyed the subject at school. I just saw a great TED talk:   The talk states that the current largest known prime is $2^{57885161}-1$  This got me thinking - how does one actually prove whether a number this large is prime or not?  Is it just done by brute force via a computer algorithm or are there any well known mathematical techniques for doing so?  I would be really grateful for any pointers as I am eager to learn about these techniques (if they exist). Smooth option sometimes produces incorrect arrow tips in PGFplots It seems that the smooth option applied to lines sometimes effects the arrow tips and produces incorrect results.  No problem with vertical lines, but any other seems to have a problem. Is this a known bug, or is there a reason why the smooth should not be applied to straight lines?  Updated: to show problem does NOT occur with TikZ, and problem also occurs with curves if smooth option is applied.  \documentclass{article} \usepackage{pgfplots} \begin{document}  \tikzstyle{MyStyle}      =[-&gt;, black, ultra thick,       ] \tikzstyle{MyStyleSmooth}=[-&gt;, black, ultra thick, smooth]  \begin{tikzpicture} \begin{axis}     % 'smooth' option seems to have no effect on lines '1' and '2'     \addplot [MyStyle      , green ] coordinates{(0,0) (0,1)} node [above] {1};     \addplot [MyStyleSmooth, blue  ] coordinates{(1,0) (1,1)} node [below] {2};     %     % But, can't seem to have the 'smooth' on lines, '4', '5' and '6'     \addplot [MyStyle      , orange] coordinates{(2,0)   (3,0)   } node [right] {3};     \addplot [MyStyleSmooth, red   ] coordinates{(4,0)   (2,0.5) } node [below] {4};     \addplot [MyStyleSmooth, red   ] coordinates{(2,1)   (3,1)   } node [left ] {5};     \addplot [MyStyleSmooth, red   ] coordinates{(3,0.8) (2,0.8) } node [right] {6};      % Similar problem with curves: "non-smooth" is ok, "smooth" is not     \addplot[MyStyle,       mark=none, domain=0:1,samples=50, blue] (x,x*x+1);     \addplot[MyStyleSmooth, mark=none, domain=0:1,samples=50, red ] (x,x*x+2);  \end{axis} \end{tikzpicture}  \begin{tikzpicture} % These are all fine     \draw [MyStyle      , green ] (0,0)   -- (0,1)    node [above] {1};     \draw [MyStyleSmooth, blue  ] (1,0)   -- (1,1)    node [above] {2};     %     \draw [MyStyle      , orange] (2,0)   -- (3,0)    node [right] {3};     \draw [MyStyleSmooth, red   ] (4,0)   -- (2,0.5)  node [below] {4};     \draw [MyStyleSmooth, red   ] (2,1)   -- (3,1)    node [right] {5};     \draw [MyStyleSmooth, red   ] (3,0.8) -- (2,0.8)  node [left ] {6}; \end{tikzpicture} \end{document} ST_Length (GEOM, true) for calculating distances in Geographic Reference System Calculate the sum of the infinite series $\sum_{n=0}^{\infty} \frac{n}{4^n}$ A previous problem had us solving $\sum_{n=0}^{\infty} \frac{1}{4^n}$ which I calculated to be $\frac{4}{3}$ using a bit of mathematical manipulation.   Wonderful. Thank you for all the prompt responses.  Could anyone suggest an alternate technique that does not involve differentiation? If $H \leq G$ and $[G:H]! \leq |G|$ then $G$ is not simple I would like to find a way to construct uncountably many non-isomorphic linear (total) orderings of natural numbers (as stated in the title).  I've already constructed two non-isomorphic total orderings. They are $$ 1 &lt; 2 &lt; 3 &lt;\ldots\\ 1 &gt; 2 &gt; 3 &gt;\ldots $$ where "$&lt;$" and "$&gt;$" are  strict total ordering relations.  Thanks in advance for your help. Why is the edit button disabled? I edited some questions before, but now I get an error message when clicking the edit button. I thought there was a problem with the specific question, but I cannot click it on any question.  What's going on? What is the best way to repeatedly execute a function every x seconds? What's the easiest way to set up a LAMP stack? I set up a new VPS instance of Ubuntu and am wondering what the easiest way is to get up and running with a basic LAMP stack (i.e. which packages are required, which configuration options need to be tweaked, if any, etc.). How to create script with auto-complete? I searched all over this site and the web for a good and simple example of autocomplete using jQuery and ASP.NET. I wanted to expose the data used by autocomplete with a webservice (and will probably do that next). In the meantime, I got this working, but it seems a little hacky...  In my page I have a text box:  &lt;input id="txtSearch" type="text" /&gt;   I am using jQuery autocomplete, set up per their example:  &lt;link rel="stylesheet" href="js/jquery.autocomplete.css" type="text/css" /&gt; &lt;script type="text/javascript" src="js/jquery.bgiframe.js"&gt;&lt;/script&gt; &lt;script type="text/javascript" src="js/jquery.dimensions.pack.js"&gt;&lt;/script&gt; &lt;script type="text/javascript" src="js/jquery.autocomplete.js"&gt;&lt;/script&gt;   Here is where it starts to get hacky... I call a page instead of a webservice:    &lt;script type="text/javascript"&gt;     $(document).ready(function(){         $("#txtSearch").autocomplete('autocompletetagdata.aspx');     });         &lt;/script&gt;   In the page I stripped out ALL of the html and just have this (otherwise, various HTML bits show up in the autocomplete dropdown):  &lt;%@ Page Language="C#" AutoEventWireup="true" CodeFile="autocompletetagdata.aspx.cs" Inherits="autocompletetagdata" %&gt;   And in my autocompletetagdata.aspx, I am using SubSonic to query, format and return data from the database (one data item per line):  protected void Page_Load(object sender, EventArgs e) {     // Note the query strings passed by jquery autocomplete:     //QueryString: {q=a&amp;limit=150&amp;timestamp=1227198175320}      LookupTagCollection tags = Select.AllColumnsFrom&lt;LookupTag&gt;()         .Top(Request.QueryString["limit"])         .Where(LookupTag.Columns.TagDescription).Like(Request.QueryString["q"] + "%")         .OrderAsc(LookupTag.Columns.TagDescription)         .ExecuteAsCollection&lt;LookupTagCollection&gt;();      StringBuilder sb = new StringBuilder();      foreach (LookupTag tag in tags)     {         sb.Append(tag.TagDescription).Append("\n");     }      Response.Write(sb.ToString()); }   If you don't do a LIKE query, then it returns everything that contains a match for the character(s) you type -- e.g., typing "a" will include "Ask" and "Answer" as well as "March" and "Mega." I just wanted it to do a starts with match.  Anyway, it works and it's pretty easy to set up, but is there a better way?