Which is the better choice to choose whether timestamp or datetime.. I'm currently  working in mysql . for date and time field in database table which is the better one?? and the reason to choose it??
Would you recommend using a  or a  field, and why (using MySQL)?   I'm working with PHP on the server side.
$\frac{1}{A_1A_2}=\frac{1}{A_1A_3}+\frac{1}{A_1A_4}$.Then find the value of $n$ If $A_1A_2A_3.....A_n$ be a regular polygon and $\frac{1}{A_1A_2}=\frac{1}{A_1A_3}+\frac{1}{A_1A_4}$.Then find the value of $n$(number of vertices in the regular polygon).  I know that sides of a regular polygon are equal but i could not relate$A_1A_3$ and $A_1A_4$ with the side length.Can someone assist me in solving this problem? I was just watching a mega factory video and wondered why they use an AC motor which requires a power inverter instead of DC which may be powered directly from their DC battery? Introducing an inverter means more cost (weight, controller, etc).  Are there any reasons for that? What are the differences between an AC and DC motor that may have lead to this decision? Also does anyone know what kind of motor is used in other electric cars? Is there any way other than instanceof operator for object type comparison in java? Regexp that matches valid regexps Installing Nvidia drivers on Red Hat Is there a way to get trig functions without a calculator? In school, we just started learning about trigonometry, and I was wondering: is there a way to find the sine, cosine, tangent, cosecant, secant, and cotangent of a single angle without using a calculator?  Sometimes I don't feel right when I can't do things out myself and let a machine do it when I can't.  Or, if you could redirect me to a place that explains how to do it, please do so.  My dad said there isn't, but I just had to make sure.  Thanks. I'd love to see if there are trends over time, patterns of improving behaviour after being flagged, consistent reoffenders, most misused types of flag, etc.  I understand the who-said-what-about-who aspect would most likely cause this to be denied, but even anonymised data would be interesting to dig through. I get this error: dpkg: unrecoverable fatal error, aborting: files list file for package `fonts-tlwg-kinnari' contains empty filename If I were to attack with a 4/4 indestructible creature and it's blocked by a 4/2 creature with first strike, would my indestructible creature still attack during the second combat damage step, or would it just tap, not assigning any damage? Car accident, put in park or neutral? Multiple Sub Query using child parent relationship Consider in my basket, I have a package (Main Product-just a holder) which will have 2 standalone products (child) and again the standalone products will have child products (Grand Parent). All these products are from same object called Product Configuration.   We have a child relationship to itself(Parent Configuration) using a custom lookup field. The problem here is, I could only fetch details only up to 1 level (i.e.,package and child details) and I was not able to drill deeper to grand child products.  Query I used to get 1 level of relation ships is below:  SELECT id, name, Access_Type__c, Circuit_Bandwidth_Value__c, QuoteType__c,     Upstream_Speed_Value__c, IP_Address_Type__c, Care_Level__c, Base_Plan_Value__c, Site_Address__c,      cscfga__Quantity__c, Quantity_of_Ip_Address__c, cscfga__Contract_Term__c, Connection_Price__c,      Monthly_Rental_Conga__c, Total_Annual_Rental__c,      (         SELECT id, name,cscfga__Product_Family__c,Upstream_Speed_Value__c, cscfga__Quantity__c, Quantity_of_Ip_Address__c,              Connection_Price__c, Monthly_Rental_Conga__c,cscfga__Parent_Configuration__r.Circuit_Bandwidth_Value__c,Circuit_Bandwidth_Value__c          FROM cscfga__Related_Configurations__r         WHERE cscfga__Parent_Configuration__c &lt;&gt; ''          ORDER BY name     )  FROM cscfga__Product_Configuration__c  WHERE cscfga__Product_Basket__r.cscfga__Opportunity__c='{pv0}'      AND cscfga__Product_Basket__r.csordtelcoa__Synchronised_with_Opportunity__c=True     AND cscfga__Parent_Configuration__c = ''  ORDER BY name   Not sure how to write another sub query to get grand child details. When I tried the below query:  SELECT id, name, Access_Type__c, Circuit_Bandwidth_Value__c, QuoteType__c, Upstream_Speed_Value__c,      IP_Address_Type__c, Care_Level__c, Base_Plan_Value__c, Site_Address__c, cscfga__Quantity__c,      Quantity_of_Ip_Address__c, cscfga__Contract_Term__c, Connection_Price__c,      Monthly_Rental_Conga__c, Total_Annual_Rental__c,     (         SELECT id, name, cscfga__Product_Family__c, Upstream_Speed_Value__c, cscfga__Quantity__c,              Quantity_of_Ip_Address__c, Connection_Price__c, Monthly_Rental_Conga__c, cscfga__Parent_Configuration__r.Circuit_Bandwidth_Value__c, Circuit_Bandwidth_Value__c,         FROM cscfga__Related_Configurations__r         WHERE cscfga__Parent_Configuration__c &lt;&gt; ''          ORDER BY name     ),     (         SELECT id, name, cscfga__Product_Family__c          FROM cscfga__Related_Configurations__r         WHERE cscfga__Parent_Configuration__c &lt;&gt; ''          ORDER BY name     ) FROM cscfga__Product_Configuration__c  WHERE cscfga__Product_Basket__r.cscfga__Opportunity__c='0066E000002Xrr0'      AND cscfga__Product_Basket__r.csordtelcoa__Synchronised_with_Opportunity__c=True      AND cscfga__Parent_Configuration__c = ''  ORDER BY name   I got below error:     MALFORMED_QUERY:  from cscfga__Related_Configurations__r ^ ERROR at   Row:6:Column:6 Cannot follow the same aggregate relationship twice:   cscfga__Related_Configurations__r   Can someone please help here. Note: I am executing these queries in Workbench. connectedness of uniform topology So I need to find the Convergence Radius and Convergence Domain of the complex power series: $\sum\limits_{n=0}^\infty \frac{1}{2^{n}} z^{2^n}$  I've tried looking at the individual parts of the series and rewriting it somehow but couldn't find a way.  It can probably be solved, after a step or two, by the formula $R=\frac{1}{\displaystyle\limsup_{n\rightarrow \infty}\sqrt[n]{|a_n|}}$ .  Thanks. Print programs with its proper syntax Chrome and IE 11 are fine, I'm only able to reproduce this in Firefox. Using version 27.0.1 on Windows 7. Meta as well as all the other sites are affected.        I can still see the hover effect, but the image is gone. I see this in Firebug:        The image doesn't show up in the Network tab. I am able to see the image by visiting  which goes to   I've done Ctrl-F5, I've cleared the cache and I've tried Private Browsing. Possibly related to  ? Why is my crontab not working, and how can I troubleshoot it? This is a  about using cron &amp; crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted. What is code coverage and how do YOU measure it?  I was asked this question regarding our automating testing code coverage. It seems to be that, outside of automated tools, it is more art than science. Are there any real-world examples of how to use code coverage? I'm in 17.10. Whenever I touch the screen, whether to change windows/apps, scroll within a browser, or press a button, the stupid little keyboard pops up in the bottom left corner.  I have never left Screen Keyboard enabled in Universal Access, but if I toggle it on, that's the same keyboard popping up in the bottom left corner.    In this screenshot, I'm simply touching the screen in a full-screen youtube video. You can see the menu pop up on the right, under the point where I'm touching.  I don't have a before pic, but it was similar look/color keyboard, but it was smaller, maybe half as wide, and only in the bottom left section of the screen, as opposed to stretching across the entire width. This change from little left-hand keyboard to full-width keyboard happened after following @pomsky 's advice below.    This is a . You can mark yourself affected by it to hopefully increase its received attention. Should I sign, watermark or otherwise label a framed print? And if so how? I have an opportunity to show some of my work in a small local coffee shop.  Are there any guidelines/practices to signing, labeling or watermarking a photo which is to be on display?  Or should a photo be signed, labelled or marked at all? Is signing the back of the photo and showing my name on a separate card below the frame itself the "better" way to do this?   I noticed many people on the web put a very noticeable watermark with their logo, copyright and name right on the photo.  Personally, I find this distracting as it often ruins the photograph itself often turning what could be art to kitsch. Painters most often sign the painting itself but this to me is not distracting because it is done with the painter's own hand and it often "works" with the painting. During a sunny day the walls of my house warm up (no surprise). My question: how much of this warming up (if any) comes from visible light? I associate infrared with thermal energy. If my house was floating in space (to prevent any thermal exchange with its surroundings) and I installed a giant infrared (and UV) filter between it and the sun, would it still warm up (compared to its rest temperature in full darkness)?