sql - rails order by time with reversed 24 hour periods -

-

i have model stores events each have start time.

the start time handled rails time, stored in postgres datetime (i'm assuming) , rails ignores date , stores 2000-01-01...

the problem have ordering events start after midnight show afterwards , not before. how can sort them differently , split events in 24 hour period first morning 12 hour events show after second half of evening events. (if makes since)

any ideas?

c=event.last c.event_items.order(:time_start)

which order \"event_items\".time_start asc"

+-----+----------+-----------+-------------------------+---------+-------------------------+-------------------------+ | id  | event_id | artist_id | time_start              | area_id | created_at              | updated_at              | +-----+----------+-----------+-------------------------+---------+-------------------------+-------------------------+ | 155 | 63       | 111       | 2000-01-01 00:40:00 utc |         | 2013-08-24 21:21:57 utc | 2013-08-26 00:07:44 utc | | 153 | 63       | 133       | 2000-01-01 01:10:00 utc |         | 2013-08-24 21:21:57 utc | 2013-08-26 00:07:44 utc | | 152 | 63       | 128       | 2000-01-01 02:00:00 utc |         | 2013-08-24 21:21:57 utc | 2013-08-26 00:07:44 utc | | 151 | 63       | 148       | 2000-01-01 22:10:00 utc |         | 2013-08-24 21:21:57 utc | 2013-08-26 00:07:44 utc | | 194 | 63       | 124       | 2000-01-01 23:00:00 utc |         | 2013-08-26 00:07:44 utc | 2013-08-26 00:07:44 utc | | 154 | 63       | 98        | 2000-01-01 23:50:00 utc |         | 2013-08-24 21:21:57 utc | 2013-08-26 00:07:44 utc | +-----+----------+-----------+-------------------------+---------+-------------------------+-------------------------+

i dates before 12h (24h clock) come after 12h+...

eg in example order 22:10, 23:00, 23:50, 00:40, 01:10, 02:00

there date_part function in postgres think this

event.order("cast(date_part('hour', time_start) integer)/12 desc,              cast(date_part('hour', time_start) integer)%12 asc")

if want divide time in different modular try different divider.

update

i guess need elaborate bit.

basically extract hour part of time_start timestamp , convert (or cast) integer want work integer not time. if divide hour 12 give interval, have on link postgres doc above more details.

so first expression cast(date_part('hour', time_start) integer)/12 give either 0 or 1; 0 if hour before 12 , 1 12 onwards. want, put hours after 12 on top of hours after 12. sorted 23 > 12, 11 > 0 though, not want.

hence second cast(date_part('hour', time_start) integer)%12. give use 23 => 11, 22 => 10 ... 12 => 0 , 11 => 11 ... 0 => 0 etc. can sort them in ascending order.

by way, doesn't sort minutes may want add time_start asc third sort criteria. think add cast(date_part('hour', time_start) integer) select statement , name refer name on order by.

hope :)


Comments

Post a Comment

Popular posts from this blog

java - activate/deactivate sonar maven plugin by profile? -

-
i use sonar plugin executes if activated in maven profile. sonar runs on every compile. the problem build fail other team members not have sonar application installed locally. pom.xml checked in team members same copy including sonar configuration, don't want them modify purpose of disabling sonar (they might inadvertently check modified copy in). please advise how configure maven (.m2/settings.xml) and/or pom.xml sonar feature can enabled/disabled local profile. here sonar configuration in each project's pom.xml: <plugin> <groupid>org.codehaus.mojo</groupid> <artifactid>sonar-maven-plugin</artifactid> <version>1.0</version> <executions> <execution> <id>make-sonar</id> <phase>compile</phase> <goals> <goal>sonar</goal> </goals> </execution> </executions> ...
Read more

python - TypeError: can only concatenate tuple (not "float") to tuple -

-
i'm new python, question might easy, anyway, patience: as trying call newton-raphson method calculate implied volatility in black-scholes formula call/put option pricing, first thing is, newton method in scipy.optimize seems calculate function's zeros, in black-scholes formula, want function's value option price, not zero. (i'm new here programming, i'm not sure techniques.) should write function things like: def f(sigma, price): return bsformula(s0,k,r,t,q,sigma) - price then, while calling newton method, takes args=() 1 parameter in function, write this: value = newton(bsprice2, 0.5, args=price) but error message: file "bs.py", line 36, in bsimpvol value = newton(bsprice2, 0.5, args=float(price)) file "/usr/lib/python2.7/dist-packages/scipy/optimize/zeros.py", line 143, in newton q0 = func(*((p0,) + args)) typeerror: can concatenate tuple (not "float") tuple could tell me why that? how fix it? apprecia...
Read more

java - What is the difference between String. and String.this. ? -

-
this question has answer here: meaning of .this , .class in java 2 answers i'll straight point. im still learning bit of syntax , want know difference between code is code a: public class buttonz extends jbutton{ public buttonz(){ settext(new string(string.valueof(i))); } } please ignore fact i undeclared, not lost. code b: public class buttonz extends jbutton{ public buttonz(){ settext(new string(string.this.charat(i))); } } what don't yet understand difference in typing string.this , string. i under assumption when use dot operator on class accessing it's static methods(and/or variables if they're not hidden). i have studied little bit , have concluded when using string. accessing string static methods.. when using string.this. i'm accessing methods class buttonz extendi...
Read more