I want to select "Apple" then output "John" and "Michelle". I try to run the code but it is not working. Please help.  select @start := title as 'title', id, parent from mytable join  (select @start := 0) temp where parent = @start and title = "Apple";   Link :
Assume you have a flat table that stores an ordered tree hierarchy:  Id   Name         ParentId   Order  1   'Node 1'            0      10  2   'Node 1.1'          1      10  3   'Node 2'            0      20  4   'Node 1.1.1'        2      10  5   'Node 2.1'          3      10  6   'Node 1.2'          1      20   Here's a diagram, where we have [id] Name.  Root node 0 is fictional.                          [0] ROOT                           /    \                [1] Node 1          [3] Node 2               /       \                   \     [2] Node 1.1     [6] Node 1.2      [5] Node 2.1           /            [4] Node 1.1.1   What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly indented tree?   Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly.   Pseudo code or plain English is okay, this is purely a conceptional question.  Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS?    EDITS AND ADDITIONS  To answer one commenter's ('s) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted.  The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay.  The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though.  Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable.  I have posted my own solution so you guys can pull it to pieces.
Comparison between bootstrap percentiles confidence interval and BCa confidence interval? I have generated a nonparametric percentiles bootstrap confidence interval ($32.27143, 51.08571$), and a BCA confidence interval ($33.26, 53.49$) with an initial sample size of $n=7$.  Evidently, the BCA interval is larger than the percentiles interval. Shouldn't the BCA interval be better than the percentiles interval (and by "better" I mean "smaller")? I noticed also that when the sample size is larger, for example $n=40$, BCa confidence interval decreases. There are no compact minimal surfaces How can I get two Xbox 360's to be in "open nat" mode behind the same router? I have two Xbox 360's, one WiFi and the other wired through the same Linksys E3000 router with DD-WRT (v24-sp2 (04/13/11) std-usb-nas firmware).   Mine (the wired one, though hers has been wired in the past and it didn't appear to help) always seems to be open (green), and hers is either moderate or closed (oj/red)  Even with the original router firmware I've never been able to get both consoles into "open nat" mode, and it makes playing certain games together almost impossible for me and my wife  because we can't seem to get into the same game.   I have uPnP enabled and the DMZ disabled, and some minor port forwarding to allow for a Minecraft server (Ports 25565 and 25566 for a testing copy of the server), but other than that the settings are mainly at their default, on the xbox's and the router.   Are there any settings I can configure to allow this to work properly? nameref (hyperref) evaluating counter instead of section name What's the proper way to reference a section with a counter in the title? The TOC generates correctly, but the cross references aren't so lucky.  MWE:  \documentclass[letterpaper, 12pt, twoside]{exam}  \usepackage{hyperref}  \newcounter{KSRLessonNumberCounter} \setcounter{KSRLessonNumberCounter}{1} \newcommand{\KSRSection}[2][\value{KSRLessonNumberCounter}]{         \setcounter{KSRLessonNumberCounter}{#1}         \section*{Lesson \arabic{KSRLessonNumberCounter}: #2}         \addcontentsline{toc}{section}{Lesson \arabic{KSRLessonNumberCounter}: {#2}}         \stepcounter{KSRLessonNumberCounter} } \newcommand{\KSRSubsection}[1]{         \subsection*{#1}         \addcontentsline{toc}{subsection}{#1} } \newcommand{\KSRLessonNumber}{ }  \begin{document}  \KSRSection{Sample}  This is the first lesson. The second lesson is \nameref{sec:blah}.  \KSRSection{Blah} \label{sec:blah}  This is the second section  \KSRSection{Lorem Ipsum}  Dollars are Set in \nameref{sec:blah}.  \end{document} individual tick label style with pgfplots given the following code, I want to modify the tick labels in such a way, that for negative values of x, the labels are located above the x-axis. How can I realize this?  \documentclass{report} \usepackage{pgf} \usepackage{pgfplots} \pgfplotsset{compat=newest} \pgfplotsset{plot coordinates/math parser=false} \begin{document} \begin{tikzpicture} \begin{axis}[% axis x line=middle, axis y line=middle, width=10cm, height=10cm, scale only axis, xmin=-5, xmax=5, xtick={-4, -2, 0,  2,  4}, xticklabels={$-4\pi$, $-2\pi$, $0$, $2\pi$, $4\pi$}, extra x ticks={-4, -2}, ymin=-1.4, ymax=1.4, ytick={-1,  0,  1}] \end{axis} \end{tikzpicture}% \end{document} I'd like to know if there is a way to run  program/shell script without typing full path:  /opt/idea/bin/idea.sh I am looking for an adjective/noun for someone who is able to speak/ makes speeches very well and uses words effectively to influence/impress people. How do I insert a backslash inside a mathematical statement? I'm trying to write a set subtraction operation in an AMS formatted template.  In the end, what I want should look like A\B.  But I'm doing this in math-mode $A\B$ and this gives me errors.  I've also tried using the \diagdown symbol, but it doesn't work either.  Is there another way to do this? Compare classifiers based on AUROC or accuracy? I have a binary classification problem and I experiment different classifiers on it: I want to compare the classifiers. which one is a better measure AUC or accuracy? And why?  Raondom Forest: AUC: 0.828  Accuracy: 79.6667 %            SVM: AUC: 0.542  Accuracy: 85.6667 % How to check if a macro value is empty or will not create text with plain TeX conditionals? I have a macro which holds some text value, e.g. \macro{some text}. If it is empty, I would like for nothing to appear in the document, but it has some content of any kind which would produce text displayed in the document, I would like a message to appear, "Text: some text".   \macro{} would be considered empty. \def\somedata{}, \macro{\somedata} would be considered empty. \macro{0} would be considered not empty.   I have tried making a TeX conditional which can check if the value is not empty, but nothing I tried works, e.g.:  \ifx #1 {} \else     Text: #1 \fi  \ifx#1{} \else     Text: #1 \fi  \ifx #1 \nil \else     Text: #1 \fi  \ifx#1!="" \else     Text: #1 \fi   What is the correct syntax for creating a conditional in plain TeX with checks if a value is not empty? How about a difficulty rating for questions? It might be useful to add a drop down field "Difficulty" for questions. With a very limited set of options, say:   Beginner Advanced Expert   This way, users could easily judge if they can answer a specific question (depending on their experience in the topic) and how much time it will probably take.  Beginners usually know they are new so they can easily select Beginner. Those with some experience just select Advanced and those working on a topic for years may chose Expert. I think it's not very difficult to judge halfway correctly.  And the difficulty rating does not have to be very precise anyway, it's more a rough estimate by the asking person.  As an addition, rep gained on this topic can be multiplied with a difficulty factor. This would solve the problem of lots of rep for often-viewed and easy to answer questions and few rep for less-viewed, difficult questions.  Update  Thank you so far for the answers. I clearly underestimated the fact that some users are going to always chose Expert difficulty.  Maybe readers voting on the difficulty would be a workaround. Of course, we cannot use the rep factor then, for the same reason.  This kind of voting would obviously introduce a whole new set of issues, since we could vote on both content and difficulty (I'm almost positive this kind of proposal existed before?). The problem statement is: for $a,b$ coprime, prove that there exists positive integers $x,y$ such that $ax-by=1$.  The question is form Arthur Egnels' problem solving text, and from the chapter on the pigeonhole principle.    My question: His proof begins by generating a list $a,\ldots,a(b-1)$, where he then points out that each element in this list(which proceeds sequentially) doesn't have remainder $0\pmod{b}$.  He then shows that we arrive at a contradiction if we assume that we also don't get remainder $1$ in this list $\bmod b$.  To show the contradiction in this last statement, he first states that we would have positive integers $p,q $ where $ 0&lt;p&lt;q&lt;b$ so that $pa\equiv qa \pmod{b}$.  He then goes on to point out that since we $a$ and $b$ are coprime, we then have that $b| q-p$.  I understand the last part here, but don't see why we get $pa\equiv qa \pmod{b}$.  Thanks in advance Forecast total for a year given monthly time series I have a monthly time series (for 2009-2012 non-stationary, with seasonality). I can use ARIMA (or ETS) to obtain point and interval forecasts for each month of 2013, but I am interested in forecasting the total for the whole year, including prediction intervals. Is there an easy way in R to obtain interval forecasts for the total for 2013? Akhil showed that the  is the same as the continuum, using as a step the observation that continuous functions that agree at rational points must agree everywhere, since the rationals are dense in the reals.  This isn't an obvious step, so why is it true? Why is the comma splice an error? It's always drilled into us that we shouldn't use comma splices. They're bad, to be avoided and poor form.  But why? What makes the comma a faulty choice in something like this:     I never liked school, it was boring and repetitive most of the time.   It could be replaced with a semicolon, dash, period or colon and be "correct." Yet to a fair amount of people, the comma seems fine. If it weren't, it wouldn't be found so often in online forums, text messages, emails and so on.  What makes the comma between two sentences an error? Determine which app is drawing on top of other apps? Microscopic interpretation of pressure in liquids When closing a question as a duplicate there is a text box which says: "search, or enter a question link or numeric id". You can copy and paste a question link into here, but this fails if the URL starts with https:// instead of http://, with the message "Your search returned no matches; please try a different search". What is $P(X > 0 \mid X + Y > 0)$ given that $X, Y$ are i.i.d standard normal? Formula Assistance I am creating a formula variable in a Flow but keep getting this error. Crop net Acres is a Number field. IF(     ISBLANK( [Opportunity].Crop_Net_Acres__c),     0,      ( [Opportunity].Crop_Net_Acres__c) )  Error Message:  netAcresFormula (Formula) - The formula expression is invalid: Syntax error. Missing '='  Any thoughts here?