sql - How to select different percentages of data based in a column value? -

-

i need query table have "gender" column, so:

 | id | gender | name    | ------------------------- | 1  | m      | michael | ------------------------- | 2  | f      | hanna   | ------------------------- | 3  | m      | louie   | -------------------------

and need extract first n results have, example 80% males , 20% females. so, if needed 1000 results want retrieve 800 males , 200 females.

  1. is possible in single query? how?

  2. if don't have enough records (imagine have 700 males on example above) possible select 700 / 300 automatically?

basically, want many 'm' can, not more percentage , enough 'f' have total 1000 rows:

with cte_m (     select * table1 gender = 'm' limit (1000 * 0.8) ), cte (     select *, 0 ord cte_m     union     select *, 1 ord table1 gender = 'f'     order ord     limit 1000 ) select id, gender, name cte

sql fiddle demo


Comments

Post a Comment

Popular posts from this blog

java - JavaFX 2 slider labelFormatter not being used -

-
i have following code not label slider "foo50", etc... 1 expect setlabelformatter call, instead seems have no effect (the slider labelled 50, 100, etc , println's dont run). there missing? not implemented in default 2.2 skin? using oracle java 7 package javafxbugtest; import javafx.application.application; import javafx.scene.*; import javafx.scene.control.*; import javafx.stage.*; import javafx.util.stringconverter; public class javafxbugtest extends application { @override public void start(final stage primarystage) { slider cp = new slider(); cp.setlabelformatter(new stringconverter<double>() { @override public string tostring(double t) { system.out.println("nope?"); return "foo" + t.tostring(); } @override public double fromstring(string string) { system.out.println("he
Read more

Detect support for Shoutcast ICY MP3 without navigator.userAgent in Firefox? -

-
the current version of mozilla firefox 23.0.1, version not support play mp3 shoutcast streams tcp port different 80 (most common 8000 shoutcast 1.9.8). i use flash when mp3 support not available in html5 audio, way detect is: try{ var = document.createelement('audio'); r = !!(a.canplaytype && !!a.canplaytype("audio/mpeg; codecs=mp3").replace(/^no$/,'')) }catch(e){ r = false; } the support mp3 shoutcast streams in firefox added in version 24 . a.canplaytype("audio/mpeg; codecs=mp3") = in chrome , firefox, chrome support, firefox not support, due current code detect not work firefox. the current version of jquery support ie 6 1.10.2, version not has .browser i think "stylized" way testing features , not querying browsers / versions, notwithstanding here see hard not violate "principle". what "stylized" way of detect mp3 icy support without navigator.useragent in firefox? ther
Read more

web - SVG not rendering properly in Firefox -

-
i have problem svg renderring in firefox. whilst works in safari, chrome or in ie, doesn't work in firefox. inspecting element seems layers there, background visible if it's z-index higher z-index of others. rendered in firefox: svg logo in firefox link original source file: svg file thanks help. ps: used sketch 3 export svg. if helps somehow. you're experiencing bug 995813 . i fixed bug time ago change still making way through release process example display correctly firefox 31 onwards released on 22 july 2014. in meantime if move fill="white" <mask> element child <use> element work around firefox bug.
Read more