postgresql - How can I average this data every 15 minutes? -


i have table called historic:

create table historic (     id serial not null         constraint table_name_pkey             primary key,     film_name varchar,     category varchar,     time_utc timestamp ) ;  create unique index table_name_id_uindex     on historic (id) ;

i have table measurements data:

create table measurements (     id serial not null         constraint measurements_pkey             primary key,     historic_rowid integer not null         constraint measurements_historic_id_fk             references historic,     measurement double precision ) ;  create unique index measurements_id_uindex     on measurements (id) ;

as can see, table measurements contains foreign key historic_rowid historic table (on rowid).

i need choose category, sci-fi. want then, measurements select records matching sci-fi category , include time:

select h.film_name, h.category, m.measurement, h.time_utc historic h left join measurements m on m.historic_rowid == h.id h.category = 'sci-fi';

the result table following columns:

film_name, category, measurement, time_utc

now, want average data every 15 minutes. in other words, want "bin" data 15 minute intervals , each "bin", average.

my final result this:

film_name, category, measurement, time_window --------------------------------------------- film_a,    sci-fi,    0.234234,    0_to_15 film_b,    sci-fi,    0.692859,    15_to_30 film_c,    sci-fi,    0.875854,    30_to_45 film_d,    sci-fi,    0.583465,    45_to_60 film_e,    sci-fi,    0.265334,    60_to_75 film_f,    sci-fi,    0.152545,    75_to_90 ....

how can this? i'm rather rubbish sql , use help.

update

as requested, here sample data time_utc field:

2017-04-18 02:31:03 2017-04-18 02:31:12 2017-04-18 02:31:27 2017-04-18 02:31:38 2017-04-18 02:31:53 2017-04-18 02:32:08 2017-04-18 02:32:17 2017-04-18 02:32:22 2017-04-18 02:32:58 2017-04-18 02:33:07 2017-04-18 02:33:12 2017-04-18 02:33:22 2017-04-18 02:33:37 2017-04-18 02:33:47 2017-04-18 02:34:32 2017-04-18 02:34:43 2017-04-18 02:34:47 2017-04-18 02:34:58 2017-04-18 02:35:02 2017-04-18 02:35:12 2017-04-18 02:35:17 2017-04-18 02:35:22 2017-04-18 02:35:32 2017-04-18 02:35:37 2017-04-18 02:35:42 2017-04-18 02:35:52 

with m15 (select generate_series('2017-04-18 00:00:00','2017-04-18 00:00:00','15 minutes'::interval) g) select h.film_name, h.category, avg(m.measurement), g historic h left join measurements m on m.historic_rowid == h.id join m15 on m15.g > time_utc , m15.g + '15 minutes'::interval < time_utc h.category = 'sci-fi' group h.film_name, h.category, g

join need outer join if want include empty intervals of course. , need define minimum , maximum generate_series - doable select min(time_utc) , max(time_utc)


Comments

Post a Comment

Popular posts from this blog

python - Operations inside variables -

this question has answer here: evaluating mathematical expression in string 12 answers i want make python script finds maximum possible output using 2 operations. problem says there syntax error @ 2nd last line, in b in there. how can fix it? x = 0 = int(input("1st number:")) c = int(input("2nd number:" )) e = int(input("3rd number:" )) in range(4): if == 0: b = "+" elif == 1: b = "-" elif == 2: b = "/" else: b = "*" j in range(4): if j == 0: d = "+" elif j == 1: d = "-" elif j == 2: d = "/" else: d = "*" k = b c d e print(k) if you're after variables e on single line, couldn...
Read more

Generic Map Parameter java -

i having lot of methods of type: public static list<eduusers> getdetails(class c, map<string, integer> params) { list<eduusers> details = null; session session = hibernateutil.getsessionfactory().opensession(); transaction tx = null; try { tx = session.begintransaction(); criteria cr = session.createcriteria(c); (map.entry<string, integer> entry : params.entryset()) { cr.add(restrictions.eq(entry.getkey(), entry.getvalue())); } details = cr.list(); tx.commit(); } catch (exception asd) { log.debug(asd.getmessage()); if (tx != null) { tx.commit(); } } { session.close(); } return details; } i trying have generic method them , have written far: public static <t> list<t> getdetails(class<t> c, class<t> b) { l...
Read more

arrays - What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it? -

what arrayindexoutofboundsexception mean , how rid of it? here code sample triggers exception: string[] name = {"tom", "dick", "harry"}; for(int = 0; i<=name.length; i++) { system.out.print(name[i] +'\n'); } your first port of call should documentation explains reasonably clearly: thrown indicate array has been accessed illegal index. index either negative or greater or equal size of array. so example: int[] array = new int[5]; int boom = array[10]; // throws exception as how avoid it... um, don't that. careful array indexes. one problem people run thinking arrays 1-indexed, e.g. int[] array = new int[5]; // ... populate array here ... (int index = 1; index <= array.length; index++) { system.out.println(array[index]); } that miss out first element (index 0) , throw exception when index 5. valid indexes here 0-4 inclusive. correct, idiomatic for statement here be: for (int index = 0; index <...
Read more