greatest-n-per-group

问题 I have a table with records for each zip code in the united states. For the purposes of displaying on a map, I need to select X random records per state. How would I go about doing this? 回答1: Use: WITH sample AS ( SELECT t.*, ROW_NUMBER() OVER (PARTITION BY t.state ORDER BY NEWID()) AS rank FROM ZIPCODES t) SELECT s.* FROM sample s WHERE s.rank <= 5 回答2: SELECT * FROM ZipCodes ORDER BY NEWID() 来源： https://stackoverflow.com/questions/3998573/sql-server-pull-x-random-records-per-state

问题 Ok i got this table +-----+-----------------------------+-------------+-------------+----------+---------+ | id | title | created | updated | category | content | +-----+-----------------------------+---------------------+---------------------+----+ | 423 | What If I Get Sick and Die? | 2008-12-30 | 2009-03-11 | angst | NULL | | 524 | Uncle Karl and the Gasoline | 2009-02-28 | NULL | humor | NULL | | 537 | Be Nice to Everybody | 2009-03-02 | NULL | advice | NULL | | 573 | Hello Statue | 2009

问题 I tried this query on MySQL server (5.1.41)... SELECT max(volume), dateofclose, symbol, volume, close, market FROM daily group by market I got this result: max(volume) dateofclose symbol volume close market 287031500 2010-07-20 AA.P 500 66.41 AMEX 242233000 2010-07-20 AACC 16200 3.98 NASDAQ 1073538000 2010-07-20 A 4361000 27.52 NYSE 2147483647 2010-07-20 AAAE.OB 400 0.01 OTCBB 437462400 2010-07-20 AAB.TO 31400 0.37 TSX 61106320 2010-07-20 AA.V 0 0.24 TSXV As you can see, the maximum volume is

问题 Am trying to find the min value from past 30 days, in my table there is one entry for every day, am using this query SELECT MIN(low), date, low FROM historical_data WHERE name = 'bitcoin' ORDER BY STR_TO_DATE(date,'%d-%m-%Y') DESC LIMIT 7 But this value not returing the correct value. The structure of my table is Table structure And table data which is store is like this Table data style Now what i need is to get the minimum low value. But my query not working it give me wrong value which

问题 Am trying to find the min value from past 30 days, in my table there is one entry for every day, am using this query SELECT MIN(low), date, low FROM historical_data WHERE name = 'bitcoin' ORDER BY STR_TO_DATE(date,'%d-%m-%Y') DESC LIMIT 7 But this value not returing the correct value. The structure of my table is Table structure And table data which is store is like this Table data style Now what i need is to get the minimum low value. But my query not working it give me wrong value which

问题 I checked other solutions to similar problems, but sqlite does not support row_number() and rank() functions or there are no examples which involve joining multiple tables, grouping them by multiple columns and returning only top N results for each group at the same time. Here's the code i run db = sqlite3.connect('mydb') cursor = db.cursor() cursor.execute( ''' CREATE TABLE orders( id INTEGER PRIMARY KEY, product_id INTEGER, client_id INTEGER ) ''' ) cursor.execute( ''' CREATE TABLE clients(

问题 There are a lot of SQL Top N questions on stackoverflow but I can't seem to find one that matches the situation I'm having. I would like to perform some grouping within a top n query. My data looks like this (obviously with fake values). MY_DATE IP_ADDRESS 1/1/09 999.999.999.999 1/1/09 999.999.999.999 1/1/09 999.999.999.998 ... a lot more rows The date range for the table covers several months and has many thousands of rows per month. What I would like to do is have a single query tell me

问题 I am trying to select top 2 records from a database table result that looks like this SubjectId | StudentId | Levelid | total ------------------------------------------ 1 | 1 | 1 | 89 1 | 2 | 1 | 77 1 | 3 | 1 | 61 2 | 4 | 1 | 60 2 | 5 | 1 | 55 2 | 6 | 1 | 45 i tried this query SELECT rv.subjectid, rv.total, rv.Studentid, rv.levelid FROM ResultView rv LEFT JOIN ResultView rv2 ON ( rv.subjectid = rv2.subjectid AND rv.total <= rv2.total ) GROUP BY rv.subjectid, rv.total, rv.Studentid HAVING

问题 I am trying to select top 2 records from a database table result that looks like this SubjectId | StudentId | Levelid | total ------------------------------------------ 1 | 1 | 1 | 89 1 | 2 | 1 | 77 1 | 3 | 1 | 61 2 | 4 | 1 | 60 2 | 5 | 1 | 55 2 | 6 | 1 | 45 i tried this query SELECT rv.subjectid, rv.total, rv.Studentid, rv.levelid FROM ResultView rv LEFT JOIN ResultView rv2 ON ( rv.subjectid = rv2.subjectid AND rv.total <= rv2.total ) GROUP BY rv.subjectid, rv.total, rv.Studentid HAVING

问题 I am trying to select top 2 records from a database table result that looks like this SubjectId | StudentId | Levelid | total ------------------------------------------ 1 | 1 | 1 | 89 1 | 2 | 1 | 77 1 | 3 | 1 | 61 2 | 4 | 1 | 60 2 | 5 | 1 | 55 2 | 6 | 1 | 45 i tried this query SELECT rv.subjectid, rv.total, rv.Studentid, rv.levelid FROM ResultView rv LEFT JOIN ResultView rv2 ON ( rv.subjectid = rv2.subjectid AND rv.total <= rv2.total ) GROUP BY rv.subjectid, rv.total, rv.Studentid HAVING