mysql - Update and select count at the same time taken too much time -

-

i have mysql statement:

update student_performance_cache spc set badges = (select count(ub.mb_no) user_badges ub ub.mb_no=spc.student_id)

i got problems query taken time when data become larger. how can improve mysql statement , make faster?


Comments

Post a Comment

Popular posts from this blog

python - argument must be rect style object - Pygame -

-
disclaimer: know other people on site have had error it's been in different contexts , fixes don't seem work here. hey stackoverflow, i've been making sideways space invaders game, ship follows mouse's y position stays on left, , clicking shoots bullet. enemies spawn randomly right , fly left, , objects removed once each side of screen. works fine, when tried implement collision detection see when shot hits enemy, error: typeerror: argument must rect style object. it points line "return hitbox.colliderect(target.rect)". try , work out causing made 'print' lines below see 'target.rect' (and whether proper rect object), , seemed same style shot's own rect, i'm lost why colliderect doesn't accept it. i've annotated pretty everything, sorry if it's insult intelligence should make things easier. class causes problems: class gameobject: def __init__(self, image, height, speed): self.speed = speed self.image...
Read more

webrtc - Which ICE candidate am I using and why? -

-
[questions in bold below] i have setup kurento media server 5.1.3 in datacenter behind firewall running os ubuntu 14.04. has 2 network cards: 222.222.222.222 (eth0 - private ip) 111.111.111.111 (eth1 - public ip) attached below sdp (setremotedescription) when browser connected kurento media server type: answer, sdp: v=0 o=- 5487318114793304426 0 in ip4 0.0.0.0 s=kurento media server c=in ip4 0.0.0.0 t=0 0 a=group:bundle audio video m=audio 59068 rtp/savpf 111 0 c=in ip4 111.111.111.111 a=rtpmap:111 opus/48000/2 a=rtpmap:0 pcmu/8000 a=sendrecv a=rtcp:59068 in ip4 111.111.111.111 a=rtcp-mux a=ssrc:669011897 cname:user39019747@host-6e83e4c2 a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time a=mid:audio b=as:20 a=ice-ufrag:ymdk a=ice-pwd:lylifk5ueqzpwm91ddj37e a=fingerprint:sha-256 ff:0f:81:8c:41:4e:b4:b6:c6:d8:36:f3:d6:5f:09:fd:5f:af:13:b3:9d:fc:12:66:ac:f3:56:d6:5b:0a:73:5d a=candidate:1 1 udp 2013266431 111.111.111.111 55239 typ host a=candidate:2 1 udp...
Read more

c# - Better 64-bit byte array hash -

-
i need hash algorithm produces 64-bit hash code ( long ) fewer collisions string.gethashcode() , fast (no expensive calls cryptographic functions). here's implementation of fnv still shows 3% of collisions after testing 2 million random strings. need number way lower. void main() { const string chars = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz!#@$%^&*()_+}{\":?><,./;'[]0123456789\\"; const int n = 2000000; var random = new random(); var hashes = new hashset<long>(); int collisions = 0; for(int = 0; < n; i++) { var len = random.next(chars.length); var str = new char[len]; (int j = 0; j < len; j++) { str[j] = chars[random.next(chars.length)]; } var s = new string(str); if(!hashes.add(get64bithash( s ))) collisions++; } console.writeline("collision percentage after " + n + " random strings: " + ((doubl...
Read more