Get an random String from MySQL with Java I'm actually have the Problem that I don't know how to get a random  nickname from my Table called "nicks" where the column called "nicknames".  Here is an example what I've.  private String getNames() {     String names= "";     try {         ResultSet rs = Core.getSQL().getResultSet("SELECT * FROM nicks");          names = rs.getString("nicknames");     } catch (Exception e) {         e.printStackTrace();     }     return names;   } }   Can someone pls tell me why I only get the String "" and how I can get just one random entry out of my database?  Hope that someone can help me.
How to request a random row in SQL? How can I request a random row (or as close to truly random as is possible) in pure SQL?
As far as I know, ping needs to create a  (which needs either root access or cap_net_raw capabilities). From my understanding the trend these last years has been to remove  binaries and replaced them with . However when I look at the ping binary on my Fedora 32, it doesn't look to have any: $ ls -la $(which ping) -rwxr-xr-x. 1 root root 82960 May 18 10:26 /usr/bin/ping $ sudo getcap -v $(which ping) /usr/bin/ping $     Does ping need to open raw socket on fedora? Or is there another way to give it the permission to open a raw socket? Vortex in liquid collects particles in center At xmas, I had a cup of tea with some debris at the bottom from the leaves.  With less than an inch of tea left, I'd shake the cup to get a little vortex going, then stop shaking and watch it spin.  At first, the particles were dispersed fairly evenly throughout the liquid, but as time went on (and the vortex slowed, although I don't know if it's relevant) the particles would collect in the middle, until, by the time the liquid appeared to almost no longer be turning, all the little bits were collected in this nice neat pile in the center.  What's the physical explanation of the accumulation of particles in the middle?  My guess is that it's something to do with a larger radius costing the particles more work through friction... How do I calculate the determinant of the following $n\times n$ matrices  $$\begin {bmatrix} 0 &amp; 1 &amp; \ldots &amp; 1 \\ 1 &amp; 0 &amp; \ldots &amp; 1 \\ \vdots &amp; \vdots &amp; \ddots &amp; \vdots \\ 1 &amp; 1 &amp; ... &amp; 0 \end {bmatrix}$$  and the same matrix but one of columns replaced only with $1$s?  In the  above matrix all off-diagonal elements are $1$ and diagonal elements are $0$. Creating a link using an 18 character ID I have an 18 character SFDC ID. I was under the impression that I should be able to create a link to that record using the following pattern: https://&lt;org server&gt;.salesforce.com/&lt;id&gt;  For example: https://na12.salesforce.com/00TU000000Nf5NP  That link works fine for me. However, when I try to link to the same object using the 18 character, case insensitive ID (ex. https://na12.salesforce.com/00tu000000nf5npmaz), I get the following error:     Insufficient Privileges      You do not have the level of access necessary to perform the operation   you requested. Please contact the owner of the record or your   administrator if access is necessary.   What exactly is the problem? If all I have is the 18 character ID, how can I create a link back to the correct SalesForce record? Creating Workflow -> Error Lagrangian of Schrodinger field The usual Schrodinger Lagrangian is $$ \tag 1 i(\psi^{*}\partial_{t}\psi ) + \frac{1}{2m} \psi^{*}(\nabla^2)\psi, $$ which gives the correct equations of motion, with conjugate momentum for $\psi^{*}$ vanishing. This Lagrangian density is not real but differs from a real Lagrangian density  $$ \tag 2 \frac{i}{2}(\psi^{*}\partial_{t}\psi -\psi \partial_{t}\psi^{*} ) + \frac{1}{2m} \psi^{*}(\nabla^2)\psi $$ by a total derivative.  My trouble is that these two lagrangian densities lead to different conjugate momenta and hence when setting equal time commutation relations, I am getting different results (a factor of 2 is causing the problem). I can rescale the fields but then my Hamiltonian also changes. Then applying Heisenberg equation of motion, I don't get the operator Schrodinger equation.   Is it possible to work with the real Lagrangian density and somehow get the correct commutation relations? I would have expected two Lagrangians differing by total derivative terms to give identical commutation relations (since canonical transformations preserve them). But perhaps I am making some very simple error. Unless all conjugate momenta are equivalent for two Lagrangians differing by total derivatives, how does one choose the correct one?   I guess the same thing happens for other first order systems like Dirac Lagrangian also. Quantum Hall effect for dummies In the past few days I've become increasingly intrigued by the QHE, mainly thanks to very interesting questions and answers that have appeared here. Unfortunately, I am as of yet very confused by all the (seemingly disparate) stuff I learned.  First, here are some random points that I've been able to gather   I(nteger)QHE occurs due to the presence of Landau levels IQHE is an embodiment of topological order and the states are characterized by the Chern number that tells us about topologically inequivalent Hamiltonians defined on the Brillouin zone IQHE requires negligible electron-electron interations and so is dependent on the presence of impurities that shield from Coulomb force F(ractional)QHE occurs because of formation of anyons. In this case Coulomb interaction can't be neglected but it turns out an effective non-interacting description emerges with particles obeying parastatistics and having fractional charge FQHE has again something to do with topology, TQFT, Chern-Simons theory, braiding groups and lots of other stuff FQHE has something to do with hierarchy states   So, here are the questions        Most importantly, do these points make sense? Please correct any mistakes I made and/or fill in other important observations   How do explanations 1. and 2. of IQHE come together? Landau quantization only talks about electron states while topological picture doesn't mention them at all (they should be replaced by global topological states that are stable w.r.t. perturbations)   How do explanations 4., 5. and 6. relate together   Is there any accessible introductory literature into these matters?   Do IQHE and FQHE have anything (besides last three letters) in common so that e.g. IQHE can be treated as a special case? My understanding (based on 3.) is that this is not the case but several points hint into opposite direction. That's also why I ask about both QHE in a single question Who should own files shared by a group and where should they go Can we have a moderator only "flag for community team/developer attention" link on posts? How do I remove this wall plate with no visible screws? I'm amazed how complicated this wall plate is to remove. It is made of plastic and accommodates a phone jack and a coaxial cable. Please see the images that accompany this question. I've searched it thoroughly and there are no tabs anywhere on the face or edges to press in. There are no screws. I've pulled on it pretty hard, hoping that it would pop off, but if I pulled any harder it surely would break. Of course, I had the coaxial off while I tried to remove the plate. The brand name on the phone jack part is &quot;KRONE&quot;. Has anyone seen a wall plate like this? If so, how do you remove it? I have to say, I'm absolutely blown away by how ridiculously difficult this is. Any help would be appreciated. Is there a formal proof for $(-1) \times (-1) = 1$? It's a fundamental formula not only in arithmetic but also in the whole of math. Is there a proof for it or is it just assumed? There are many lengths in LaTeX. For instance, \enskip, \enspace, \quad, \parskip, \smallskip, ...  Some of them are mostly used for vertical spacing, some others are mostly used for horizontal spacing, and perhaps some of them are used in both cases. I wonder whether there is a list that indicates the meaning and intended use of each length in LaTeX.  By "intended use" I mean not only whether the length is vertical or horizontal, but in which circumstances it is a good practice to use that specific length. Kinetic energy conservation in collision.  In any type of collision type of collision if we take the system to comprised of both bodies then the net external force is zero. So the work done by external force is also zero. By the relation $W=K_f-K_i$ as $W$ is zero hence kinetic energy is conserved. But this not the case.   Can you tell me what is the flaw in my argument? Some people say that the argument has neglected the fact that some kinetic energy is transformed into heat. But heat is created due to the interactions between bodies during collision which is thus an internal force and thus shouldn't affect kinetic energy. Troubleshooting for biber Where is composition tab in QGIS Composer to change page size? I am trying to change the page size in the QGIS 3.0 Composer but I am not able to see the Composition tab.  I have right clicked an empty space in the toolbar but did not see anything about composition.  I am using Windows 7.  I tried looking at the QGIS docs but they are still in testing. What does the Visual Studio "Any CPU" target mean? What is the proper usage of "not only... but also"? I'm trying to figure out how to use "not only... but also" properly. Basically, my goal is to combine two clauses by using "not only".  For negations, I've figured out two styles that both sound correct:   He knew that if he fractures his finger, not only would he not be able to compete in the water polo tournament, he would not be able to take the SAT on Monday, either. He knew that if he fractures his finger, neither would he be able to compete in the water polo tournament, nor would he be able to take the SAT on Monday.   However, I don't know how to form a sentence that does not include a negation while using "not only". Here are a few possibilities that I've considered:   Thanks to his remarkable performance on the SAT, not only was he accepted into Harvard, but he was also given a full scholarship. Thanks to his remarkable performance on the SAT, not only was he accepted into Harvard, but he was given a full scholarship. Thanks to his remarkable performance on the SAT, not only was he accepted into Harvard, he was given a full scholarship. Thanks to his remarkable performance on the SAT, not only was he accepted into Harvard, he was also given a full scholarship.   In those four possibilities, I'm varying the usage of "but" and "also" in the last clause.  What is the proper usage of "not only"? Solutions to $a+b+c=12$, $a, b, c \in \mathbb{N}_0$ Let $a, b, c \in \mathbb{N}_0$. If $a+b+c=12$, how many solutions $(a,b,c)$ satisfy the equation?   Is the answer:      $729$ Proving that $n$-cycle has order $n$ Do I cast the result of malloc? In , someone suggested in a  that I should not cast the result of malloc. i.e., I should do this: int *sieve = malloc(sizeof(int) * length);  rather than: int *sieve = (int *) malloc(sizeof(int) * length);  Why would this be the case?