what is the error in the following mysql statement
How can I prevent SQL injection in PHP?
I would like to automate some services using cron jobs.  When I try to edit the crontab file at /etc/crontab, I am not able to save it as it says that it is read only.   What can I do? Prove the inequality and limitation Suppose $\{a_k\}$ ,$\{b_k\}$ and $\{\xi_k\}$ are non negative, and for all $k\ge 0$ , we have $$a_{k+1}^2\le(a_k+b_k)^2-\xi_k^2$$   Prove   1.$$\sum_{i=1}^{k}\xi_i^2\le(a_1+\sum_{i=0}^kb_i)^2$$   2. If $\{b_k\}$ also satisfy $\sum_{k=0}^{\infty}b_k^2\lt+\infty $, then $$\lim_{k\to\infty}\frac{1}{k}\sum_{i=1}^k\xi_i^2=0$$   After doing this transformation:$$\xi_k^2\le(a_k+b_k)^2-a_{k+1}^2$$ $\Rightarrow$ $$\sum_{i=1}^{k}\xi_k^2\le(a_1+b_1-a_2)(a_1+b_1+a_2)+(a_2+b_2-a_3)(a_2+b_2+a_3)+\cdots(a_k+b_k-a_{k+1})(a_k+b_k+a_{k+1})$$ then I can't move forward any more. How are unmarketable market orders (other side of the order book is empty) matched with incoming orders? Crossthread operation not valid... - VB.NET Rings, ideals and units-proof Let $R$ be a ring and let $J$ be an ideal of $R$. Assume $J$ contains   a unit of $R$. Prove $J=R$, rigorously.   Again I feel here as if the statement is intuitive so I am not able to make it rigorous. If you could show all steps in the proof that would be nice. Connect two computers with SSH in a home LAN I have two ubuntu computer shared the same wifi and desire to reach another from one's terminal.  First create an user on the second computer named "Second" and hostname "Algorithms"    Then tried to reach it from the other with SSH,  but get error report as   $ ssh second@Algorithms   ssh: Could not resolve hostname algorithms: nodename nor servname provided, or not known   The solution I tried is based on   What's the problem with my experiment? Incoming light reacts with the several types of cone cells in the eye. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision. Each individual cone contains pigments composed of opsin apoprotein, which is covalently linked to either 11-cis-hydroretinal or more rarely 11-cis-dehydroretina.  The opsins (photopigments) present in the L and M cones are encoded on the X chromosome.  A very small percentage of women may have an extra type of color receptor because they have different alleles for the gene for the L opsin on each X chromosome. X chromosome inactivation means that only one opsin is expressed in each cone cell, and some women may therefore show a degree of tetrachromatic color vision. Tetrachromacy is also demonstrated among several species of birds, fish, amphibians, reptiles and insects.  Humans cannot see ultraviolet light directly because the lens of the eye blocks most light in the wavelength range of 300–400 nm.  So, besides above mentioned exceptions, is it possible due to mutations or genetic engineering to see UV or infrared. What kind of mutations should be made or are the changes to be made in the opsines to big to create 'alien' eyes? One form of Jensen's inequality is     If $X$ is a random variable and $g$ is a convex function, then   $\mathbb{E}(g(X))\geq g(\mathbb{E}(X))$.   Just out of curiosity, when do we have equality? If and only if $g$ is constant? Why can Naruto still use Rasenshuriken? When Naruto first used Rasenshuriken against Kakuzu the effect was massive. He destroyed   two of Kakuzu's hearts, but there were a huge after effect to him. If I'm not mistaken, Tsunade advised Kakashi to ask Naruto never to use the technique again due to the huge risk. So why is Naruto still able to use the technique and have no side effects after that battle? I may have missed out on something. I have this below code where i am trying to first search an account name and on hit button it displays the result set.  On the button click i am also loading an child component which is displaying the id of the record.  I need the child component should get displayed once i click on the record.  How can i achieve this -   Parent Component -   &lt;aura:component controller="SimpleAccountController"&gt;     &lt;aura:attribute name="account" type="account[]"/&gt;     &lt;ui:outputText aura:id="outName" value="" class="text"/&gt;     &lt;ui:inputText aura:id="name" label="Enter Name:" placeholder="Your Name" /&gt;     &lt;ui:button aura:id="button" buttonTitle="Click to see what you put into the field" class="button" label="Click me" press="{!c.getInput}"/&gt;     &lt;aura:iteration var="acc" items="{!v.account}"&gt;             &lt;a onclick="{!c.accountselected}" data-recId="{!acc.Id}"&gt;         &lt;p&gt;{!acc.Name} : {!acc.Type} : {!acc.Industry} : {!acc.Rating}&lt;/p&gt;             &lt;/a&gt;         &lt;c:HelloWorkdChildCmp selectedaccount="{!acc.Id}" /&gt;     &lt;/aura:iteration&gt; &lt;/aura:component&gt;   COntroller -   ({     getInput : function(cmp, evt) {         var myName = cmp.find("name").get("v.value");         var myText = cmp.find("outName");         var greet = "Hi, " + myName;         myText.set("v.value", greet);         var action = cmp.get("c.seaAcc");         action.setParams({ "s" : myName });         action.setCallback(this, function(response) {             var state = response.getState();             if (state === "SUCCESS") {                 cmp.set("v.account", response.getReturnValue());                 //alert("From server: " + response.getReturnValue());             }         });         $A.enqueueAction(action);     },      accountselected : function(cmp, evt) {        console.log(evt.currentTarget.getAttribute("data-recId")) ;     }  })   Child component -   &lt;aura:component &gt;     &lt;aura:attribute name="selectedaccount" type="String"/&gt;     &lt;div&gt;Id: {!v.selectedaccount}&lt;/div&gt; &lt;/aura:component&gt; I'm looking to find out if there's any easy way to calculate the number of ways to tile a $3 \times 2n$ rectangle with dominoes. I was able to do it with the two codependent recurrences  f(0) = g(0) = 1 f(n) = f(n-1) + 2g(n-1) g(n) = f(n) + g(n-1)   where $f(n)$ is the actual answer and $g(n)$ is a helper function that represents the number of ways to tile a $3 \times 2n$ rectangle with two extra squares on the end (the same as a $3 \times 2n+1$ rectangle missing one square).  By combining these and doing some algebra, I was able to reduce this to  f(n) = 4f(n-1) - f(n-2)   which shows up as sequence , confirming that this is the correct recurrence.  The number of ways to tile a $2 \times n$ rectangle is the Fibonacci numbers because every rectangle ends with either a verticle domino or two horizontal ones, which gives the exact recurrence that Fibonacci numbers do. My question is, is there a similar simple explanation for this recurrence for tiling a $3 \times 2n$ rectangle? I recently obtained a Seagate Expansion 3TB external harddrive. I'm trying to copy over all of my stuff to prepare for reformatting and installing a new OS. A handful of my mp3s did not transfer when I was doing my music folder. I checked them after the fact and the ORIGINAL files became corrupted somehow. I am certain of at least a few that were not corrupted in anyway before doing this. Every now and then during my transfer I got  There was an error copying the file into /media/***/Seagate Expansion Drive. Error splicing file: Input/output error   Each of these files that I check after are corrupted at some point in the duration and will not play. Why did this happen and what can I do to fix it? How to add desktop shortcut for URL, ignoring web app manifest? Goal:  Have a desktop shortcut that opens  , ignoring the contained web app manifest that otherwise "overrides" the saved shortcut to  and with "display": "standalone".  I had this working previously on an older Android phone before a replacement / upgrade.  Prior to the upgrade, I was able to long-press and open individual articles in new tabs - as well as copy link shortcuts to specific articles, as well as all of the other features and functionality that Chrome has to offer.  Here is just a partial selection of references of other users complaining about the same:       Using  provides a temporary successful work-around.  However, I can't find a successful way to add a link for this to my home screen.  The "Add to Home screen" option within Chrome instead saves a link to  - and in such a way that it opens as a web application instead of a web page within Chrome:       On a desktop operating system, this would be a non-issue.  (Create shortcut, enter desired URL, done.)  Attempt 1: Provide my own Manifest  So I created my own manifest - editing  to change the start_url attribute to https://news.google.com/news/i#0, and the display attribute from standalone to browser.  I then created my own HTML page that simply contained the below - then self-hosted both on a local web server:  &lt;html&gt;         &lt;head&gt;                 &lt;Title&gt;Google News&lt;/Title&gt;                 &lt;link rel="manifest" href="/news/manifest.json"/&gt;         &lt;/head&gt;         &lt;body&gt;                 Test         &lt;/body&gt; &lt;/html&gt;   However, this doesn't work:  Despite the shortcut being saved with the desired name and icon, it links back to my self-hosted HTML page, and not the indicated start_url.  Unfortunately, it appears that cross-domain URLs are not allowed per the manifest intent - as per  and  .  Attempt 1b: MITM website  Within the confines of my own local network, I figured I could try to  (MITM) the website to temporarily provide a desired manfiest to use for addition to the home screen.  Unfortunately, the website uses  here, which appropriately blocks the attempt.  Regardless - this is way too much work for what should be a simple effort.  Attempt 2: Widget Bookmark  Unfortunately, it looks like the 1x1 bookmark widget was removed in Chrome 48, as per  .  The suggested work-around is to use the "Add to Home screen" feature within Chrome.  Goto 10 / see beginning.  Attempt 3: Use the default-provided "Internet" browser  Unfortunately, using "Add shortcut on Home screen" in the default-provided "Internet" browser produces the same result as Chrome.  Consideration 4: Use a custom app / widget  Could probably write and install a custom application or widget that could be added to the home screen to meet the goal.  Or don't re-invent the wheel, and use an existing one.  Some possibilities:   "More Shortcuts":  "Shortcut Customizer":    Conclusion  How can someone create a desktop shortcut to an arbitrary URL, ignoring a provided web app manifest? How to Install Ubuntu on separate hard drive in a dual boot? I have already installed Windows 7 on C: drive. Now I want to install Ubuntu on E: drive which is a free partition. How do I proceed? I am trying to update to install PHP 5.5, 5.6 or 7.0 in Ubuntu 12.04/14.04/16.04 LTS, and I can only get PHP 5.3.10 for Ubuntu 12.04, PHP 5.5.9 for Ubuntu 14.04 or PHP 7.0.4 for Ubuntu 16.04 using official repositories (using apt-get).  I'm not really sure how to do a manual update – as I need:   to play around with the new(est) PHP features to install older PHP version due support in the software How can the behavior of InterpolationOrder->0 be controlled? NB: Nvidia has released an official fix; please see ,  and/or .  Upon waking up Ubuntu 16.04 from Suspend, the following graphical glitches appear around all windows, context menus, and similar:      This is currently known to affect the following NVIDIA cards running the proprietary drivers:  NVIDIA GeForce 610M, driver version 375.39, 340.102 NVIDIA GT 630M, driver version 375.39 NVIDIA GTX 650, driver version 375.39 NVIDIA GT 740M, driver version 378.13 NVIDIA GTX 745, unknown driver version NVIDIA GTX 850M, driver version 375.39, 378.13 NVIDIA GT 940M, driver version 375.39 NVIDIA GTX 950M, unknown driver version NVIDIA GTX 960M, driver version 378.13 NVIDIA GTX 970, driver version 375.39 NVIDIA GTX 970M, driver version 375.39 NVIDIA GTX 980 TI, unknown driver version NVIDIA GTX 1060, driver version 375.26, 375.39, 378.09 NVIDIA GTX 1070, driver version 378.09  The above above list has been sourced from reports from other users here on AU,  thread, and  thread. NB: This is be no means an exclusive list. It probably effects nearly all Nvidia cards.  Furthermore, this issue has been replicated on a clean install where the only change was a software update and the installation of the latest NVIDIA drivers.  What is going on, and how can it be resolved? I have the following diagram:  \documentclass{article} \usepackage{amsmath,amsfonts,graphicx} \usepackage{algpseudocode} \usepackage{tikz, nth} \usetikzlibrary{arrows.meta,decorations,decorations.pathreplacing,calc,bending,positioning, chains}  \begin{document} \begin{tikzpicture}[scale=0.6]         \draw[thick,]  (0,8) -- (0,0) node[left] {0};         \draw[thick,]  (0,0) -- (8,0) node[right] {8};         \draw[thick,]  (8,8) -- (8,0) node[left] {};         \draw[thick,]  (8,8) -- (0,8) node[left] {8};          \draw[thick,]  (4,0) -- (4,8) node[left] {};          \fill (1, 4) circle[radius=2.5pt] node[below]{$A$};         \fill (2, 6) circle[radius=2.5pt] node[below]{$B$};         \fill (3, 2) circle[radius=2.5pt] node[below]{$C$};         \fill (4, 8) circle[radius=2.5pt] node[below]{$D$};         \fill (7, 3) circle[radius=2.5pt] node[below]{$E$};         \fill (6, 1) circle[radius=2.5pt] node[below]{$F$};         \fill (5, 7) circle[radius=2.5pt] node[below]{$G$};         \fill (3, 8) circle[radius=2.5pt] node[below]{$H$}; \end{tikzpicture} \end{document}   How can I position the caption of the node $D$ both below and left, so that the line doesn't obscure the caption? Arrays, linked lists and other data structures in cmd.exe (batch) script I am learning Linux and I was trying the gzip command. I tried it on a folder which has a hierarchy like  Personal/Folder1/file1.amr Personal/Folder2/file2.amr Personal/Folder3/file3.amr Personal/Folder4/file4.amr   I ran     "gzip -r Personal" and now its like  Personal/Folder1/file1.amr.gz Personal/Folder2/file2.amr.gz Personal/Folder3/file3.amr.gz Personal/Folder4/file4.amr.gz   How do I go back?