Sorry for my english I'm french :D,  Okay, i use pdo for my connexion with MySQL, but i have one error with PDO prepare statement.  I try to include my table name into the prepare request but i have an error :  Error : SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''NbClient' LIMIT 2) as sr' at line 1 Error Code : 42000   My code :   &lt;html&gt;     &lt;head&gt;     &lt;/head&gt;      &lt;body&gt;     &lt;?php      const HOST='localhost';     const DBNAME='GameWave';     const USER='';     const PASSWORD='';     const TABLE='NbClient';      echo GetNbClientByHour(2);       function GetNbClientByHour($nb_heure)     {                $hookConstTable = TABLE;           try         {             $pdo_options[PDO::ATTR_ERRMODE] = PDO::ERRMODE_EXCEPTION;             $connexion = new PDO('mysql:host='.HOST.';dbname='.DBNAME, USER, PASSWORD, $pdo_options);              $prepare=$connexion-&gt;prepare('select SUM(record) from (select v_tot as record from :tab LIMIT :nb_heure) as sr;');             $prepare-&gt;bindParam(':tab', $hookConstTable, PDO::PARAM_STR);             $prepare-&gt;bindParam(':nb_heure', $nb_heure, PDO::PARAM_INT);             $prepare-&gt;execute();              $resultat = $prepare-&gt;fetch();             $prepare-&gt;closeCursor();              return $resultat[0];         }                     catch(Exception $e)         {             echo 'Error : '.$e-&gt;getMessage().'&lt;br /&gt;';             echo 'Error Code : '.$e-&gt;getCode();         }     }     ?&gt;     &lt;/body&gt; &lt;/html&gt;   But if i try to write table name in request, its work ...  $prepare=$connexion-&gt;prepare('select SUM(record) from (select v_tot as record from NbClient LIMIT :nb_heure) as sr;'); $prepare-&gt;bindParam(':nb_heure', $nb_heure, PDO::PARAM_INT);   Could you help me please ?
Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh-&gt;prepare('SELECT * FROM :table WHERE 1'); if ($stmt-&gt;execute(array(':table' =&gt; 'users'))) {     var_dump($stmt-&gt;fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"
Question about how to interpret arbitrary elements I have a question about how to interpret arbitrary elements. When we say:  &quot;let $x$ be an arbitrary integer&quot;  &quot;let $x$ be any integer&quot;  &quot;let $x$ be an integer&quot;   at the beginning of proofs, are we saying:  &quot;let the symbol $x$ represent one of the integers, although it is not clear which specific integer the symbol $x$ represents&quot;.  If not, please let me know how I should think about the above statements. Thank you for your time.  Edit: I had a follow up question to the one I asked earlier. What do mathematicians mean by “arbitrary element” or “any element”. I can understand when mathematicians say “let $x$ be $4$” as this means “the symbol $x$ represents $4$”. Could someone please elaborate on why the specific terms “arbitrary” and “any” are used? When I run this command :  apt install libkf5*   I get the following error :  Unable to locate package libkf5*    I'm sure that the packages whose names start with libkf5 exist (tab-completion says so) . So the problem is not about the absence of those packages.(Note the asterisk at the end of that error message , the wildcard's not working at all) I use apt v.1.9. Thanks in advance. Proof verification: Set of partial limits of a sequence is closed Mysterious! Beamer itemize has no bullets after adding a few packages this is my first time using beamer.  I copied a template from the sharelatex page on Beamer  Which works, and \begin{itemize} shows bullets     But after adding a few more packages that I need, all the bullets are gone!    What is going on and how can I fix this?  \documentclass{beamer}  \usepackage[utf8]{inputenc}    \usepackage{amsmath}  \usepackage{amsthm}     %Theorem Environment  \usepackage{amssymb}  \usepackage{multirow}  \usepackage{cancel}  \usepackage{amsfonts}  \usepackage{graphicx}  \usepackage{subfigure}  \usepackage{upgreek}     \usepackage{mathtools}  \usepackage{thmtools}  \usepackage{enumitem}       %Information to be included in the title page: \title{Sample title} \author{Anonymous} \institute{ShareLaTeX} \date{2014}  \begin{document}    \frame{\titlepage}    \begin{frame}  \frametitle{Sample frame title}  \begin{itemize} \item  This is a text in first frame.  \item This is a text in first frame. \item This is a text in first frame.  \end{itemize}  \end{frame}  \end{document} Why does the inverse of the Hilbert matrix have integer entries? Python: list items are not changed in for loop I want to find all files which contain a specific string of text. The grep command works, but I don't know how to use it for every directory (I can only do it for my current directory). I tried reading man grep, but it didn't yield any help. Could not get lock /var/lib/apt/lists/lock when I try to apt-get update I'm getting the below error,  E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable) E: Unable to lock directory /var/lib/apt/lists/ What are the rules for splitting words at the end of a line? What are the rules in English language to split words at the end of a line?   Where exactly must the hyphen split the word? Before you disagree with me with a downvote, or just want to be funny, please hear me out. From the :  The upvote privilege comes first because that's what you should focus on: pushing great content to the top. Downvoting should be reserved for extreme cases. It's not meant as a substitute for communication and editing.  I have honestly never seen a downvote reserved for an extreme case. The process is usually 1) downvote post if it's bad and don't comment. (Not much of a process, is it?) As you stay on the site longer and longer, you develop a carelessness towards downvotes (as I have), but for new users, it's really discouraging.  question inspired me to [ask balpha to] make , which is a list of users with 1 rep who have the  badge. That's the closest I could get to new users who deleted their own posts after downvotes came in. Don't get me wrong, I know the argument about being nice to new users very well, but I still believe it to be an issue. And since , users are much more inclined to go the lazy route and downvote bad questions. No alternative measures (see below) are taken, for the most part. Personally, I leave a comment and don't downvote until the asker shows no interest in fixing their post. The only other measure taken to discourage downvotes (on answers) is the -1 rep punishment to the downvoter, which is absolutely meaningless and inconsequential anyways. How are we supposed to educate new users when we don't teach them what to do, don't direct them to the FAQ, and discourage them with downvotes right off the bat?  Instead of voting down: If the post is spammy or offensive — flag it. If the question is duplicate or off-topic — flag it for moderator attention. If something is wrong, please leave a comment or edit the post to correct it.  We claim to discourage downvoting, yet I see answers like  that encourage us to downvote first and ask questions later when a question is simply unclear or effortless. It's just an awful chain reaction. A new user comes to the site asking a question, but that doesn't work out too well, so they get downvotes, delete the question in shame, and don't get the help they deserve as a fellow writer of code and programmer. Strip away the quality of the site for a moment: the core functionality of this site, and the only reason I and a lot of other users are (still) on it, is to receive and give help to/from others. I enjoy making sure fellow programmers get the answer they need, because this site has helped me get mine when I needed them. Quality can still be maintained if content is fixed rather than downvoted more often. So can we stop discouraging new users from continuing to use this site and actually start to discourage downvoting? I think we need to encourage effort towards teaching and helping new users understand the system and why their post is bad rather than slapping them in the face with downvotes that they don't know how to interpret anyways. I'm leaving ways we can do this up to others. My first thought was to increase the punishment for downvoting answers and to no longer make question downvotes free, but those wouldn't be well-received, judging by the history of similar suggestions. . Wireless connection fails every few minutes I was reading the following article by Mathew Might.  I saw the following the paragraph  What doesn't matter GPA? I don't care if it's 2.0 or 4.0. I won't even look at it. The school you went to? I'll judge you the same whether you went to Nowhere State U or a top-ten school. Transcripts? Never seen one. GREs? Irrelevant. Where you work/worked? Unless it's a research lab, it's not important. I don't think these items have much predictive capacity as to whether or not someone can complete a Ph.D.  Is Mathew Might telling the truth? For me it's very hard believe that GPA, GRE scores and undergraduate school don't matter. I used to think that they play an extremely important role in grad school admission. What is an example of Gâteaux differentiable but not Fréchet differentiable at a point in a finite-dimensional space? Let $V,W$ be nonzero normed spaces over $\mathbb{K}$ such that $V$ is finite-dimensional.  Let $E$ open in $\mathbb{K}$ and $p\in E$.  Let $f:E\rightarrow W$ be Gâteaux-differentiable at $p$.  Is $f$ necessarily Fréchet-differentiable at $p$ in this case?  I think this is not true in general, but cannot find a counterexample. What would be a counterexample? Generalizing a sequence. Consider a sequence of the form:  $x[n]=-1,-1...,1,1,...,-1,-1...,1,1... \quad n&gt;0$  One can think of this as a square wave ($\pm1$) with a 50 % duty cycle (coming from EE).  For the simplest case of such a series i.e. $-1,+1,-1,+1,-1...$, a general equation is quite trivial ($x[n]=-1^n$).  Can we have e general equation for the other cases i.e. when there are multiple $-1$'s followed by $+1$'s ? Gravatar profile image not showing sometimes It seems that with some profiles the Gravatar image is broken. I am not sure if this is an issue with SE or Gravatar, or both, so posting here.  As an example,  shows an error on , which shows a HTTP 500 on Gravatar.  Profile image on SO:        Image on Gravatar:        Switching to the MSE profile of the user, the image is working (but has a different hash).  Is this a bug on the SE side? Can anything be done to make Gravatar fix this?    Update 2016-10-04:  It happened to me again two times today. The last user profile was . Calling the service two or three times fixes the issue. It is being surprisingly hard to achieve. I've tried so far:   Download file manager apps from Google Play. Unfortunately, "share" shares the files, not the file names. None of them had a option like copy file names Download backup apps. Unfortunately, none of them backup the file names of a folder.   Any idea to copy to the clipboard or share the file names of all the files of a folder? SEDE should pick up on changes to community metadata It appears that site meta data isn't updated in SEDE. As an example, Moderators.SE was  to  in December 2014. It is still listed in SEDE as Moderators.SE, as of July 2015.  To search for Community Building data, we need to search the "Moderators" community:    It is not listed as Community Building: Using Joint Distributions and conditional probabilities This exercise is particularly confusing me because I do not understand the distribution of 'X-Y' or how to calculate the probabilities Why is $1$ not considered a prime number?  Or, why is the definition of prime numbers given for integers greater than $1$? Unit testing code which has logic around the CreatedDate An example of the problem would be trying to test a trigger on a case which will fire on update, and look for time differences between when a case was created and now. Ideally in the unit tests I want to create a case with a CreatedDate in the past. The problem here is that CreatedDate is an audit field and not writeable[1]. Is there a standard work around to this problem?  [1] I know you can get audit fields turned on to be writeable temporarily when doing data migration. This is not a viable solution for every time you want to get your code coverage up for deployment.