How to run join query on multiple tables ?
Multiple tables join in SQL for this scenario
Why Doesn't a Bootable USB Boot This question is asked often in Ask Ubuntu, sometimes with few hints about the situation.   Please provide a list of possible reasons to help troubleshoot the problem. This is a Q&amp;A that I recently have figured out, so I have posted the answer below.  After installing Windows 10, every time I get a kernel update or I run the update-grub2 it always shows Windows 7 or Windows Recovery Environment instead of Windows 10.  How do I fix this permanently? Is it "re-offend" or "reoffend"? I want to know whether there is a hyphen in the word re-offend, or if it is spelt reoffend. I looked in Oxford English dictionary and the word "reoffend" appears, but then I checked Merriam-Webster and the word is not in there.  So is reoffend a word or is it re-offend?  I'm in Australia where we observe UK English if that matters. How to calculate the exact probability that the second player wins? Consider a game that uses a generator which produces independent random integers between 1 and 100 inclusive. The game starts with a sum S = 0. The first player adds random numbers from the generator to S until S > 100 and records her last random number 'x'. The second player, continues adding random numbers from the generator to S until S > 200 and records her last random number 'y'. The player with the highest number wins, i.e. if y > x the second player wins. Is this game fair? Write a program to simulate 100,000 games. What is the probability estimate, based on your simulations, that the second player wins? Give your answer rounded to 3 places behind the decimal. For extra credit, calculate the exact probability (without sampling).     import random  CONST_TIMES = 100000 CONST_SMALL = 100 CONST_LARGE = 200  def playGame():     s = 0     while s &lt;= CONST_SMALL:          x = random.randint(1, CONST_SMALL)         s = s + x;     while s &lt;= CONST_LARGE:         y = random.randint(1, CONST_SMALL)         s = s + y     if x &lt; y:         return 's'     elif x == y:         return 'm'     else:         return 'f'  fst = sec = 0 for i in range(CONST_TIMES):     winner = playGame()     if winner == 'f':         fst = fst + 1     elif winner == 's':         sec = sec + 1 secWinPro = round(float(sec) / CONST_TIMES, 3)  print secWinPro   The simulation probability is about 0.524. I want to know how to calculate the exact probability. Recent fluid-mechanical experiments by the groups of Couder in Paris and Bush at MIT, mimic a surprisingly wide range of quantum effects. The essential ingredient of these fluid-mechanical systems is a background or pilot-wave that guides the droplets.  Now, surprisingly, a simple analysis of a Bell-type experiment shows that, in the presence of a background field, one of the premises of the Bell inequality, namely measurement independence (MI), is violated. See the paper  (available ). Therefore such classical droplet experiments could violate a Bell inequality. More importantly, if this analysis is correct, background-based hidden-variable theories are admissible, even if they are local (in the sense of ‘involving only (sub)luminal interactions’) and even if they are compatible with free will.   My question: to me the analysis seems fully sound, but maybe there is still an unphysical hypothesis that slipped in ? How to define a recurrence relation in Maple without the command proc? When you discard cards at the beginning of the game, where do they go? The appearance is that they get shuffled back into the deck. However, after discarding key cards and not receiving them the whole game, I am now wondering if they get put in the bottom of the deck. Where do they go after being discarded? Help with a proof. Countable sets. What is the meaning of “runneth” in ? How to limit current of an AC signal For my project, I'm trying to work with the principle of electrovibration. This principle is about simulating textures using low current electricity on an insulated conductive surface ().  In order to do this, I will be experimenting with generated AC signals of 80 to 160 Vpp at 60Hz to 400Hz. I will do this by using an DC - AC converter, usually used for EL lamp applications.  My only concern is how to limit the current coming from the converter. Are the techniques for limiting AC current the same as DC, by using a simple resistor? Or is it, as I expect, more complex?  I need to limit the current to 0.5mA, for safety reasons. My overall upgrade went well, but I am left with a critically lingering issue of mysql-server not being able to install itself, and nothing I am trying gets it to work.  This is the error I see when trying to install/reinstall it:  Setting up mysql-server-5.7 (5.7.11-0ubuntu6) ... Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details. invoke-rc.d: initscript mysql, action "start" failed. dpkg: error processing package mysql-server-5.7 (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of mysql-server:  mysql-server depends on mysql-server-5.7; however:   Package mysql-server-5.7 is not configured yet.  dpkg: error processing package mysql-server (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                    Processing triggers for systemd (229-4ubuntu4) ... Processing triggers for ureadahead (0.100.0-19) ... Errors were encountered while processing:  mysql-server-5.7  mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1)   I've tried completely removing it, though doing so attempts to install MariaDB because of dependencies (?). Any suggestions on what I can do to fix this would be most welcome.  EDIT: Looks like I'm not the only one: Where in the registry does Windows store with which program to open certain file types? After installing Adobe PDF reader, it opens files with the .PDF file extension. Ones' default web browser opens .html files and notepad opens .txt files, etc.  Where exactly in the registry are these filetype - program associations stored in the registry?   In other words, how does Windows know with which software/program it must open a certain file(type)? Similar to my old question about  are there any limits to the animal forms an Animagus can be?     We know that the animal form can be much smaller than human (cat, rat, beetle) so I don't think size is a factor.   I'm not aware of any Animagus who transforms into a magical creature (e.g. unicorn or phoenix) so maybe those aren't possible.   Ultimately, what I'd like to know is whether there could be a T-Rex Animagus... (prompted by ) Exact relationship between electric field and intensity I often see $I(t)\propto |E(t)|^2$. What is the exact form ? Which constants are missing to make this an equality and why are they so often omitted ? More Generating Functions problems Why energy curves spacetime? This  explains how energy curves spacetime. But I would like to know why energy curves spacetime, is there something like particle interaction that produce this result? How to simplify the summation kk! without using induction? $$\sum_{k=1}^nk(k!)$$  I know the answer is (n+1)!-1..I can solve this question using principle of mathematical induction...but I would like to know if there is any other alternative approach I may have missed it with the 3D, but I could have sworn I saw what I suspect was a lady Dwarf or two running from the Erebor in the beginning of the Hobbit, but they didn't seem bearded.    If dwarf women aren't bearded, then was Aragorn just kidding in the Two Towers (movie) when he intimated that they all had beards?    It's also stated by Tolkien in appendix A to The Lord of the Rings that female dwarves appear identical to males and we can assume they are also born with beards, just like their male counterparts. How to forward specific log file outside of /var/log with rsyslog to remote server? How can I forward message from a specific log file like /www/myapp/log/test.log with rsyslog client to remote rsyslog server? This log file is outside of the directory /var/log. Number Theory: Complete set of residues modulo $n$ I have this problem assigned for homework and I'm struggling with the proof of it:  If $a_1,a_2,\dotsc,a_n$ is a complete set of residues modulo $n$ and $\gcd(a,n)=1$, prove that $aa_1,aa_2,\dotsc,aa_n$ is also a complete set of residues modulo $n$.  (Hint: It suffices to show that the numbers in question are incongruent modulo $n$.)  I'm in elementary number theory so I'm not allowed to use an high-level theorems to prove this, I pretty much have to use the basics of modulo.  Thanks!