This question has probably been answered and I have found part of the solution  for Postgres.  I am running version 9.1 of Postgres and this is what I am trying to do. I have a table:   col1 |   col2    | col ------------------------   1   | 1 jan 12  | Joe   1   | 1 jan 12  | Bill   1   | 1 jan 12  | Sue   2   | 2 may 13  | Bob   2   | 2 may 13  | Mary   I want:   col1 |   col2    | col3 ------------------------   1   | 1 jan 12  | Joe, Bill, Sue   2   | 2 may 13  | Bob, Mary   I am sure the solution is simple, I just have not been able to come up with it despite searching. I am guessing that array_agg is probably part of my solution.
I am looking for a way to concatenate the strings of a field within a group by query. So for example, I have a table:  ID   COMPANY_ID   EMPLOYEE 1    1            Anna 2    1            Bill 3    2            Carol 4    2            Dave   and I wanted to group by company_id to get something like:  COMPANY_ID   EMPLOYEE 1            Anna, Bill 2            Carol, Dave   There is a built-in function in mySQL to do this
How to execute sudo commands with Expect & send commands in bash script? I've been looking for this feature in Blender, either upon the time of creation using Edge Cut and Slide or afterwards, in just editing the mesh. I'd like to know if it's possible to evenly slide two edges away from one another in Blender?  Here's a picture of what I'd like to be able to do:    Thanks upfront!! Fibonacci combinatorial identity: $F_{2n} = {n \choose 0} F_0 + {n\choose 1} F_1 + ... {n\choose n} F_n$ Can someone explain how to prove the following identity involving Fibonacci sequence  $F_n$  $F_{2n} = {n \choose 0} F_0 + {n\choose 1} F_1 + ... {n\choose n} F_n$ ? Getting javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher? Evaluate $\prod \frac {2k - 1} {2k}$ I came across to this: evaluate $$\prod_{k = 1}^{n} \frac {2k - 1} {2k}.$$  I brought it to a closed-form expression in asymptotics but I suspect my asymptotics is bad and I also want to see different solutions, hence the question.  My original solution: Write   $$\begin {eqnarray} \prod_{k = 1}^{n} \frac {2k - 1} {2k} &amp; = &amp; \exp \left (\sum_{k = 1}^{n} \log \left (1 - \frac {1} {2k}\right) \right) \nonumber \\ &amp; = &amp; \exp \left (- \sum_{k = 1}^{n} \sum_{m = 1}^{\infty} \frac {1} {(2k)^m m}\right). \end {eqnarray}$$  Let $$S = \sum_{m = 1}^{\infty} \frac {1} {(2k)^m m} \tag {1}.$$ Multiply both sides of $(1)$ by $2k$ to get $2k S &lt; S + 1$, and by $4k$ to get $4kS &gt; S + 2$. Hence, $$\frac {2} {4k - 1} &lt; S &lt; \frac {1} {2k - 1}.$$ Then, $$\frac {1} {2} \left( \log (4n - 1) - \log 3 \right) - 2 + O \left(\frac {1} {n^2}\right) &lt; \sum_{k = 1}^{n} \sum_{m = 1}^{\infty} \frac {1} {(2k)^m m} &lt; \frac {1} {2} \log (2n - 1) - 1 + O \left(\frac {1} {n^2}\right).$$ Hence, $$\sqrt {\frac {c} {2n - 1}} &lt; \prod_{k = 1}^{n} \frac {2k - 1} {2k} &lt; \sqrt {\frac {3 c^2} {4n - 1}},$$ where $c$ is a constant. Any better approach? Complete Statistic: Uniform distribution Take a random sample $X_1, X_2,\ldots X_n$ from the distribution $f(x;\theta)=1/\theta$ for $0\le x\le  \theta$.  I need to show that $Y=\max(X_1,X_2,...,X_n)$ is complete.  Now, I know I should multiply the sample distribution of $Y$ and multiply it with a function of $Y$, then integrate over the range of $\theta$ and equate them to zero. But how do I get the sampling distribution of $Y$? CSS two divs next to each other I want to put two &lt;div&gt;s next to each other. The right &lt;div&gt; is about 200px; and the left &lt;div&gt; must fill up the rest of the screen width? How can I do this? We are in the combat phase:   I declared my attackers  My opponent declared his blockers, stating which attackers he was blocking I cast an instant, which automatically kills his blocker. There is nothing blocking my attacker now   Now we're in the damage phase. I said that my attacker now does damage and  reduces my opponent's hit points. My opponent said that because my attacker was blocked no damage could be done. I pointed out that the blocker was destroyed before the damage phase, so therefore he wasn't blocking, but he wasn't having it. (My attacker does not have trample)  Is this covered by a specific section in the rules? If $G$ is isomorphic to $H$, then ${\rm Aut}(G)$ is isomorphic to ${\rm Aut}(H)$ If a group $G$ is isomorphic to $H$, prove that ${\rm Aut}(G)$ is isomorphic to ${\rm Aut}(H)$.   Can someone provide a step by step solution? Explaining along the way our strategy in proving this. Extended support for Ubuntu 12 Not sure if there is a better communication mechanism for asking this question. Ubuntu 12 is EOL April 2017. Do corporations have any option to extend support on 12?  Thanks How do I join several objects into one? It would be nice if backticked code in question titles were rendered the same way they are in question bodies. Since there are so many questions with code in them I feel it would be a big plus. .  This would look a lot nicer in listings and on the page itself if the code strings were rendered as such.  Similar ideas discussed . I have created several designs for a particular project and they are related, but I don't want to have to keep recreating any similar elements, such as shared materials or textures.  How can I use the existing data in a new Blender file? Lag compensation with networked 2D games I want to make a 2D game that is basically a physics driven sandbox / activity game. There is something I really do not understand though. From research, it seems like updates from the server should only be about every 100ms. I can see how this works for a player since they can just concurrently simulate physics and do lag compensation through interpolation.  What I do not understand is how this works for updates from other players. If clients only get notified of player positions every 100ms, I do not see how that works because a lot can happen in 100ms. The player could have changed direction twice or so in that time. I was wondering if anyone would have some insight on this issue.  Basically how does this work for shooting and stuff like that?  Thanks The add comment link and comment box overlaps bounty box Of course when you type:  sudo apt-get install whatever   It asks you:   Do you want to continue [Y/n]?    Is there any way I can just install it without it asking me if I want to continue? I don't really care about space, I have more then enough. Reading a file used by another process Method for determining irreducibles and factorising in $\mathbb Z[\sqrt{d}]$ I know that $\mathbb Z[\sqrt{7}]$ is a UFD, and I can write the equation $(2 + \sqrt{7})(3 - 2\sqrt{7}) = (5 - 2\sqrt{7})(18 + 7\sqrt{7}) $. So clearly these are not all irreducibles. How do I determine which of these aren't irreducible? How do I factor those into irreducibles?  It seems difficult when dealing with $\mathbb Z [\sqrt{d}] $ with $d$ positive, since the norm map isn't as nice (it's not always positive).  Thanks The generating function for the Fibonacci numbers How to split a very long equation (using AMSMATH package)?