jdbc - find minimum value by grouping the timestamp in sql -


how find minimum value following set or records in sql

date                       values -------------------------  ------  2013-07-20 18:05:38.599   257  2013-07-20 18:06:39.264   118  2013-07-20 18:07:39.51    142  2013-07-20 18:08:39.67    138  2013-07-20 18:09:40.279   123  2013-07-20 18:10:40.697   115  2013-07-20 18:11:41.158   124  2013-07-20 18:12:41.327   128  2013-07-20 18:13:41.797   533  2013-07-20 18:14:42.345   129  2013-07-20 18:15:42.694   124  2013-07-20 18:16:43.222   114  2013-07-20 18:17:43.715   119  2013-07-20 18:18:44.162   126

i need find minimum value every 3 min of timestamp. can please suggest query work this??

always specify dbms, , provide create table , insert statements in question.

create table test (   date timestamp,   value integer ); insert test values ('2013-07-20 18:05:38.599',   257), ('2013-07-20 18:06:39.264',   118), ('2013-07-20 18:07:39.51',    142), ('2013-07-20 18:08:39.67',    138), ('2013-07-20 18:09:40.279',   123), ('2013-07-20 18:10:40.697',   115), ('2013-07-20 18:11:41.158',   124), ('2013-07-20 18:12:41.327',   128), ('2013-07-20 18:13:41.797',   533), ('2013-07-20 18:14:42.345',   129), ('2013-07-20 18:15:42.694',   124), ('2013-07-20 18:16:43.222',   114), ('2013-07-20 18:17:43.715',   119), ('2013-07-20 18:18:44.162',   126);

use platform's date/time functions generate virtual table of "buckets", each 1 containing interval of 3 minutes. exactly how varies among sql platforms, because date/time functions vary lot among sql platforms. i'm using postgresql, i'm going use generate_series() function in common table expression. 

with buckets (   select n start_time, n + interval '3' minute end_time   generate_series(timestamp '2013-07-20 18:05:38.599',                         timestamp '2013-07-20 18:18:44.162',                         '3 minutes') n ) select min(test.value), start_time, end_time test inner join buckets on test.date >= start_time , test.date < end_time group start_time, end_time order start_time;  118  2013-07-20 18:05:38.599  2013-07-20 18:08:38.599 115  2013-07-20 18:08:38.599  2013-07-20 18:11:38.599 124  2013-07-20 18:11:38.599  2013-07-20 18:14:38.599 114  2013-07-20 18:14:38.599  2013-07-20 18:17:38.599 119  2013-07-20 18:17:38.599  2013-07-20 18:20:38.599

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