postgresql - Select limited set of fields from inner query with preserved order -


i've got sql query involves one-to-many relationships order by clause:

select    s0_.id,   s0_.created_at,   s5_.sort_order    surveys_submits s0_   inner join surveys_answers s3_ on s0_.id = s3_.submit_id   inner join surveys_questions s4_ on s3_.question_id = s4_.id    inner join surveys_questions_references s5_ on s4_.id = s5_.question_id  order    s0_.created_at desc,    s5_.sort_order asc

this query returns following results:

id  | created_at          | sort_order ----+---------------------+----------- 218 | 2014-03-18 12:21:09 | 1 218 | 2014-03-18 12:21:09 | 2 218 | 2014-03-18 12:21:09 | 3 218 | 2014-03-18 12:21:09 | 4 218 | 2014-03-18 12:21:09 | 5 217 | 2014-03-18 12:20:57 | 1 217 | 2014-03-18 12:20:57 | 2 217 | 2014-03-18 12:20:57 | 3               ...  214 | 2014-03-18 12:18:01 | 4 214 | 2014-03-18 12:18:01 | 5 213 | 2014-03-18 12:17:48 | 1 213 | 2014-03-18 12:17:48 | 2 213 | 2014-03-18 12:17:48 | 3 213 | 2014-03-18 12:17:48 | 4 213 | 2014-03-18 12:17:48 | 5

now, need modify query in way return first 25 distinct ids begining preserved order.

i've tried this:

select distinct id (    select ... order ... ) inner_query order created_at desc, sort_order asc limit 25 offset 0;

but doesn't work:

error:  select distinct, order expressions must appear in select list line 16:       created_at desc,                 ^ ********** error **********

...and can't add created_at , sort_order columns select clause cause result in duplicated ids, first query.

select * (     select distinct on (s0_.id)         s0_.id,         s0_.created_at,         s5_.sort_order              surveys_submits s0_         inner join surveys_answers s3_ on s0_.id = s3_.submit_id         inner join surveys_questions s4_ on s3_.question_id = s4_.id          inner join surveys_questions_references s5_ on s4_.id = s5_.question_id      order         s0_.id,         s0_.created_at desc,          s5_.sort_order asc ) s order     created_at desc,     sort_order asc limit 25

from manual

select distinct on ( expression [, ...] ) keeps first row of each set of rows given expressions evaluate equal. distinct on expressions interpreted using same rules order (see above). note "first row" of each set unpredictable unless order used ensure desired row appears first.


Comments

Post a Comment

Popular posts from this blog

basic authentication with http post params android -

i doing basic authentication passing username , password , using basicnamevaluepair sending post params response service. my method: public stringbuilder callservicehttppost(string username, string password, string type) { // create new httpclient , post header httpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(webservice + type); httpresponse response = null; stringbuilder total = new stringbuilder(); try { url url = new url(webservice + type); /*string base64encodedcredentials = base64.encodetostring((username + ":" + password).getbytes(), base64.url_safe | base64.no_wrap);*/ string base64encodedcredentials = "basic " + base64.encodetostring( (username + ":" + password).getbytes(), base64.no_wrap); httppost.setheader("auth...
Read more

vb.net - Virtual Keyboard commands -

i wondering difference between virtual these keyboard commands is: keyeventf_extendedkey , keyeventf_keyup is. everywhere have looked gives me description based off integers , not want know each of them does. you've tagged question vb.net, these have nothing @ vb.net. they're constants defined in windows header files, use win32 api functions. as far difference, can't tell looking @ values. individual values not particularly important, that's why named identifiers used. what's important used , documentation functions tells mean. the first one, keyeventf_extendedkey , used keybdinput structure (which used along e.g. sendinput function) pass information synthesized keyboard input. if flag used, means scan code should interpreted extended key. technically, means scan code preceded prefix byte value 224 (&he0 in hexadecimal notation). the second one, keyeventf_keyup , 1 of flags available use structure. means key being released (going up)...
Read more

How to get multiresult with multicondition in Sql Server -

i need solve this. hopefully can giving me advices. for sample, i've got data : proclib.march 1 first 10 rows flight date depart orig dest miles boarded capacity ----------------------------------------------------------------- 114 01mar94 7:10 lga lax 2475 172 210 202 01mar94 10:43 lga ord 740 151 210 219 01mar94 9:31 lga lon 3442 198 250 622 01mar94 12:19 lga fra 3857 207 250 132 01mar94 15:35 lga yyz 366 115 178 271 01mar94 13:17 lga par 3635 138 250 302 01mar94 20:22 lga 229 105 180 114 02mar94 7:10 lga lax 2475 119 210 202 02mar94 10:43 lga ord 740 120 210 219 02mar94 9:31 lga lon 344...
Read more