php - Using count(*) vs num_rows -

-

to number of rows in result set there 2 ways:

  1. is use query count

    $query="select count(*) count some_table type='t1'";

    and retrieving value of count.

  2. is getting count via num_rows(), in php.

so 1 better performance wise?

if goal count rows, use count(*). num_rows ordinarily (in experience) used confirm more 0 rows returned , continue on in case. take mysql longer read out many selected rows compared aggregation on count if query takes same amount of time.


Comments

Post a Comment

Popular posts from this blog

codeigniter - Fatal error: Call to undefined function lang() in CI Merchant using CardSave -

-
i have setup checkout using ci merchant , payment gateway provider cardsave. works using test account , test card details when trying live transaction on production account following error: fatal error: call undefined function lang() in xxx\application\libraries\merchant\merchant_cardsave.php on line 160 line 160 looks like: $this->post_redirect($acs_url, $data, lang('merchant_3dauth_redirect')); i've integrated other merchants using ci merchant , haven't come across error before , haven't been able find in google either. has come across , resolved before?
Read more

python - Received unregistered task using Celery with Django -

-
i have celery setup django project , can't seem task run properly. i'm using django 1.4.3, celery 3.0.1, django-celery 3.0.17 , python 2.7 on ubuntu 13.04. i have verified rabbitmq-server running: sudo service rabbitmq-server status status of node rabbit@fenster ... [{pid,1667}, {running_applications,[{rabbit,"rabbitmq","3.0.2"}, {os_mon,"cpo cxc 138 46","2.2.9"}, {mnesia,"mnesia cxc 138 12","4.7"}, {sasl,"sasl cxc 138 11","2.2.1"}, {stdlib,"erts cxc 138 10","1.18.1"}, {kernel,"erts cxc 138 10","2.15.1"}]}, {os,{unix,linux}}, {erlang_version,"erlang r15b01 (erts-5.9.1) [source] [64-bit] [smp:8:8] [async-threads:30] [kernel-poll:true]\n"}, {memory,[{total,28112760}, {connection_procs,93432}, {que...
Read more

c# - Delving into the world of XML (Windows Phone) Error I dont understand (The ' ' character, hexadecimal value 0x20, cannot be included in a name.) -

-
so starting learn how use xml data within app , decided use free data cannot life of me working code far. (i have done few apps static data before hey apps designed use web right? :p) public partial class mainpage : phoneapplicationpage { list<xmlitem> xmlitems = new list<xmlitem>(); // constructor public mainpage() { initializecomponent(); loadxmlitems("http://hatrafficinfo.dft.gov.uk/feeds/datex/england/currentroadworks/content.xml"); test(); } public void test() { foreach (xmlitem item in xmlitems) { testing.text = item.title; } } public void loadxmlitems(string xmlurl) { webclient client = new webclient(); client.openreadcompleted += (sender, e) => { if (e.error != null) return; stream str = e.result; xdocument xdoc = xdocument.load(str); ***xmlitems = (from ite...
Read more