Learning about joins and I understand the difference in what inner joins and left joins do,  returns rows when there is a match in both tables, and left join returns all rows from the left table, even if there are no matches in the right table. I get that. however in this example i am following along with, how they make the join confuses me: select * from person join car on person.car_id = car.car_id;  gives me every person in the db that has a car_id value that isnt null. select * from person left join car on car.car_id = person.car_id;  gives me every person in the db, regardless including those with a null car_id value; what I dont get, are why these two statements are identical (apart from the left join) but these two values are inversed: inner join: car on person.car_id = car.car_id; left join: car on car.car_id = person.car_id; can someone offer me a clear explanation as to why these statements are swapped about in the inner and left joins?
Also how do LEFT JOIN, RIGHT JOIN and FULL JOIN fit in?
Most useful additions in KOMA-Script? (Background: I'm a beginner who will mostly use LaTeX for university articles and reports, but no math. Also, as I reside in Canada, the German typography conventions, which I understand KOMA-Script supports better than LaTeX, are less relevant).  I've read that the KOMA-Script package has a lot of improvements for the default document classes. Yet the 's length, about 250 pages, is somewhat daunting. I plan to read the chapters I'm interested in anyway but it'd be useful to have some pointers about low hanging fruits. I searched the site and  answers say KOMA-Script adds improvements but do not delve into details.  I'll ask this as a community wiki topic and, since the audience of this site is international, feel free to mention German typography if KOMA-Script is better there. How can we know that all of the results for entangled photons are not chosen when the pair is created? C++ STL Vector Iterator accessing members of an Object I think I've declared a Vector with an object correctly.  But, I don't know how to access it's members when looping with Iterator.  In my code, the line --->>  cout &lt;&lt; " " &lt;&lt; *Iter;  How do I print the contents of the members?  Like *Iter.m_PackLine ???  Not sure if I used the correct terminology, but appreciate the help!  Thanks  class CFileInfo {   public:       std::string m_PackLine;       std::string m_FileDateTime;       int m_NumDownloads; };  void main() {   CFileInfo packInfo;    vector&lt;CFileInfo, CFileInfo&amp;&gt; unsortedFiles;   vector&lt;CFileInfo, CFileInfo&amp;&gt;::iterator Iter;    packInfo.m_PackLine = "Sample Line 1";   packInfo.m_FileDateTime = "06/22/2008 04:34";   packInfo.m_NumDownloads = 0;   unsortedFiles.push_back(packInfo);    packInfo.m_PackLine = "Sample Line 2";   packInfo.m_FileDateTime = "12/05/2007 14:54";   packInfo.m_NumDownloads = 1;   unsortedFiles.push_back(packInfo);   for (Iter = unsortedFiles.begin(); Iter != unsortedFiles.end(); Iter++ )  {     cout &lt;&lt; " " &lt;&lt; *Iter; // !!! THIS IS WHERE I GET STUMPED     // How do I output values of the object members?   } }  // end main How to modify a text file? How can I have one keyboard input layout and multiples languages in Ubuntu 17.10? If I have English language I can't type "'e" and get an "é", as I can do in Portuguese and Spanish.  When I manage to do that on Settings -> Region &amp; Language, I'm able to change languages, but it also changes the keyboard layout.  Is there any way to change language (Portuguese or Spanish for example) and set the keyboard input layout (US International for example)? I'd like to get a list of packages installed manually by apt or aptitude and be able to find out whether a foobar package was installed manually or automatically. Is there any neat way of doing that from the command line? If derivative of function is less than or equal to 4, prove the existence of point $c$ so $f(c)=c^2$. I am struggling to construct a simple proof of the following.  Suppose $f(x)$ is differentiable for any real value $x$ and that $f'(x) \le 4$ for all real values of x. Prove there is at most one real value $c&gt;2$ such that $f(c) =c^2$.  I am completely lost on where to start on this proof and any help would be greatly appreciated! I recently installed Ubuntu 11.10 (new install). I would like to use the Adwaita theme with Unity, but it seems that it is not available in the theme selection dialog. I know I get it there after installing gnome-shell, but is there a way to use Adwaita theme for Unity without installing gnome-shell? At the start of the movie it says:      "A long time ago in a galaxy far, far away...."   Does this mean that the entire Star Wars saga takes place in a single galaxy? To my understanding a galaxy isn't very big compared to the universe itself. Star Wars has many different sentient races, and the way they are presented suggests that most planets are host to only one of them (some exceptions like naboo). This strongly leads me to believe there should actually be more galaxies in the Star Wars universe (hehe).   Another thing, I think it's safe to assume that even if the entire saga takes place in one single galaxy, their researchers can observe other galaxies (I think we started doing that in the 1600s, and they are a lot more technologically advanced than we were back then). When Obi-wan is looking for Kamino (the rain planet with the cloners) the librarian says something like "If it's not in our records, it doesn't exist", so she must be convinced that the entire universe has been explored.    If the entire universe has been documented, why wouldn't they go to those other galaxies? The technology seems to be advanced enough to hop to another galaxy. Is there any canon material that suggest that traveling between galaxies is done? If not, is there a canon explanation why they don't? how to make a full backup of ubuntu server for another computer? I have a Ubuntu 15.10 server, which currently has a bunch of software installed on. Now, I want to make a full backup of everything there (including profiles, configs, etc...) on this computer (virtually on Parallels Desktop) for another physical computer which I've recently installed Ubuntu 15.10 server on it.  So how can I transfer this system completely into that computer? I tried PinguyBuilder and Systemback, but they were not what I wanted.  Considering that if there is a way, which would need not or at least a Internet connection (specially on physical computer) would be awesome.  Any help?  P.S: I know there are many topics for backup things, but they are not exactly for a non-gui server, or maybe I couldn't find what is suitable for me. Why is "No new release found" when upgrading from a LTS to the next? What is the purpose of the Assemblies node in Web.Config? When creating a new ASP.NET AJAX Web Application in Visual Studio 2005, the default web.config contains the following section (inside the compilation node):  &lt;assemblies&gt;     &lt;add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/&gt; &lt;/assemblies&gt;   Whether or not the assemblies node exists doesn't seem to affect the AJAX functionality.  Update panels, etc work fine regardless of whether or not the reference to System.Web.Extensions is included in Web.Config.  What's the purpose of this section, and can it be safely removed? Automatically determine tags while writing a question Can we modify "Ask question" to automatically suggests tags based on your question content.   So instead that user needs to type "team-foundation-server" or "TFS" or "TeamFoundationServer" he will see list of tags auto-populated with ajax which he (or she) can then select and it will be associated with the question. So basically only thing we need is code which will cross-match question content with list of known tags while user is typing and display results in some nice ajax-enabled list/cloud/whatever UI control. This should be separate control for tags suggestions so user still has option to use standard tag list input to type-in tags.  In this case, instead of three (or more) tag variations we would have only one tag for Team-Foundation-Server. Uncertainty principle and multiple observers My understanding is that an observer can measure the precise location of a particle so long as the corresponding uncertainty in momentum measurement is not an issue and vice-versa.    Say there is such an observer, interested in the precise position of a particular particle.  Now, consider a second, independent observer, unbeknownst to the first, who is trying to measure the exact momentum of the same particle without caring about the position.  As a thought experiment, we assume that the two observers are somehow able to access the same particle at the same time in some way without being aware of each other.  Can both observers get their desired results? Linear transformation $T:\mathbb{R}^{n}\rightarrow\mathbb{R}^{n}$ such that $T^{2}=\lambda T.$ Let $T$ be a linear transformation $T:\mathbb{R}^{n}\rightarrow\mathbb{R}^{n}$ such that $T^{2}=\lambda T$ for some $\lambda\in\mathbb{R}.$ Then which of the following is/are true?  $1.\|T(x)\|=|\lambda|\|x\|$ for all $x\in\mathbb{R}^n.$  $2.$ If $\|T(x)\|=\|x\|$ for some non-zero $x\in\mathbb{R}^{n}$, then $\lambda=\pm 1.$  $3.T=\lambda I$ where $I$ is the identity transformation on $\mathbb{R}^{n}.$  $4.$ If $\|T(x)\|&gt;\|x\|$ for a nonzero vector $x\in\mathbb{R}^{n},$ then $T$ is singular.  According to me since $T^{2}=\lambda T$ we have $T$ satisfies the polynomial $x^{2}-\lambda x.$ So choices for its minimal polynomial are $x,x-\lambda,x(x-\lambda).$ So $3$rd option is clearly incorrect and $4$th option is not satisfied if $T=I$ and hence correct one. I am confused in first two options . Please help me. Thanks in advance. Notify users of a question they closed being edited or nominated for reopening Why is the Centroid of a Triangle Shared with Its Midpoint Triangle What is the minimal set of parts for a circut with this AVR microcontroller? My Arduino Uno has a ATMEGA328P-PU microcontroller, and bunch of other stuff on the board. I'd like to program the chip without the Arduino software, and only the minimum of other components.  I want to eventually create things without the cost of Arduino, and I want to learn about the other parts on the board and add them back as as needed.  I'm comfortable with C and gcc, so I can probably figure out the software part. But what, if anything, besides these two products below, do I need to have in the breadboard with the microcontroller? Okay, this should be super easy to do but I just can't find the way.  I have a background image with a solid colour layer on top of it, and I would like to add text on top of everything in such a way that the filling of the text is the image in the background. I have tried selecting the text shape and deleting that selection shape in the solid colour layer, but it just looks wrong.   Can anyone help me with this? Many thanks in advance. How to move a database from SQL Server 2012 to SQL Server 2005 What are my options if I need to move a database from SQL Server 2012(32bit) to SQL Server 2005(64bit)?  I know I cannot:   restore a backup of the database on SQL Server 2005 detach &amp; attach   I know I can:   use import data wizard, and I tried it on one database, but it only moves data, and even that was troublesome as I needed to do a lot of work creating temp tables to maintain identity columns, recreating all FKs, indexes etc.    Is there an easier option?