SQLServerCentral.com / SQL Server 2008 / T-SQL (SS2K8) / Histogram chart in sql / Latest PostsInstantForum.NET v2.9.0SQLServerCentral.comhttp://www.sqlservercentral.com/Forums/notifications@sqlservercentral.comSun, 04 Oct 2015 03:21:48 GMT20RE: Histogram chart in sqlhttp://www.sqlservercentral.com/Forums/Topic1408210-392-1.aspxThanks Chris,Appreciate the feedback.Looks like i was close so thats always a bonus.Ive never used ntile before and it certainly looks interesting (although its not suitable for this requirement).Initially i think i will use your first suggestion and see how that goes.Thanks (and to dwain for the setup code - will come in handy)Thu, 17 Jan 2013 18:03:53 GMTmatakRE: Histogram chart in sqlhttp://www.sqlservercentral.com/Forums/Topic1408210-392-1.aspx[quote][b]matak (1/17/2013)[/b][hr]I decided to write my own for a business requirement and also after reading this great article from Dwain.[url]http://www.sqlservercentral.com/articles/Excel/91179/[/url]As everyone keeps saying if you don't understand the code then don't use it (I didn't understand enough of Dwains code to be comfortable in using it in prod).Recursive cte's are something Ive never required and really don't have the know how in them just yet.Ive borrowed (ok stolen - thanks Dwain!) Dwains initial setup code and removed all the items except those relating to float[/quote]You're welcome! Looks like ChrisM has got ya covered.Thu, 17 Jan 2013 17:39:56 GMTdwain.cRE: Histogram chart in sqlhttp://www.sqlservercentral.com/Forums/Topic1408210-392-1.aspxIt looks ok to me, apart from UNION picking up the 40th bin. When this is done, the query is quite efficient:[code="sql"];with cteHistogram (N, StartBin, EndBin, TotalCount)as( select N, @min+(@interval*(N-1)) StartBin, @min+(@interval*N) EndBin, coalesce(count(RandomFloat), 0) TotalCount from @MyTestTable cross join Tally where RandomFloat >= @min+(@interval*(N-1)) and ((RandomFloat < @min+(@interval*N) and n <= @bins-1) OR (RandomFloat <= @max and n = @bins)) group by N)select Tally.N, @min+(@interval*(Tally.N-1)) StartBin, case when Tally.N = @bins then @max else @min+(@interval*Tally.N) end EndBin, coalesce(TotalCount, 0) TotalCountfrom Tally left outer join cteHistogram on Tally.N = cteHistogram.Nwhere Tally.N <= @binsorder by Tally.N [/code]Note that min and max are the calculated range min and max values, rather than RandomFloat values. If you want RandomFloat values, try this:[code="sql"]--------------------------------------------------------------------------- calculate the range start and end for each bin;WITH Bins AS ( SELECT t.n, RangeStart = minval + (interval * (t.n-1)), RangeEnd = CASE WHEN t.n = @bins THEN maxval+1 ELSE minval + (interval * t.n) END FROM ( SELECT interval = (MAX(RandomFloat) - MIN(RandomFloat)) / @bins, minval = MIN(RandomFloat), maxval = MAX(RandomFloat) FROM @MyTestTable ) d CROSS JOIN Tally t WHERE t.n <= @bins)-- Summarise the bin contents. Min and max are actual bins.SELECT b.N, StartBin = MIN(RandomFloat), EndBin = MAX(RandomFloat), RangeStart = MIN(b.RangeStart), RangeEnd = MIN(b.RangeEnd), TotalCount = COUNT(*) FROM Bins bINNER JOIN @MyTestTable t ON t.RandomFloat >= b.RangeStart AND t.RandomFloat < b.RangeEndGROUP BY N [/code]Now, if your requirement was to split the population into 40 equal groups and summarise those groups, you could use NTILE, like this:[code="sql"]-- split the set into (@bins) roughly equal-sized populations SELECT N, StartBin = MIN(RandomFloat), EndBin = MAX(RandomFloat), TotalCount = COUNT(*)FROM ( SELECT RandomFloat, N = NTILE(@bins) OVER(ORDER BY (RandomFloat)) FROM @MyTestTable) dGROUP BY N[/code]Thu, 17 Jan 2013 03:42:05 GMTChrisM@WorkHistogram chart in sqlhttp://www.sqlservercentral.com/Forums/Topic1408210-392-1.aspxHi,Im hoping someone is able to check what Ive created for a histogram chart and can provide feedback, suggestions, improvements.(Im pretty sure there will be a few).I decided to write my own for a business requirement and also after reading this great article from Dwain.[url]http://www.sqlservercentral.com/articles/Excel/91179/[/url]As everyone keeps saying if you don't understand the code then don't use it (I didn't understand enough of Dwains code to be comfortable in using it in prod).Recursive cte's are something Ive never required and really don't have the know how in them just yet.Ive borrowed (ok stolen - thanks Dwain!) Dwains initial setup code and removed all the items except those relating to float[code="sql"]DECLARE @NumberOfRows INT ,@FStartValue FLOAT ,@FEndValue FLOAT ,@FRange FLOATSELECT @NumberOfRows = 10000-- -- Random FLOATs on the closed interval {275, 850} ,@FStartValue = 275 ,@FEndValue = 850 ,@FRange = @FEndValue - @FStartValueDECLARE @MyTestTable TABLE ( RandomFloat FLOAT)INSERT INTO @MyTestTableSELECT TOP (@NumberOfRows) RandomFloat = RAND(CHECKSUM(NEWID())) * @FRange + @FStartValue FROM sys.all_columns a1 CROSS JOIN sys.all_columns a2[/code]So here is my code - I needed the outer join to the Tally table so I could get a guaranteed unbroken (no gaps) list of bins.Im hoping the code is self explanatory but if needed (asked for) I will add in some comments.[code="sql"]declare @bins as int = 40declare @interval as floatdeclare @min as floatdeclare @max as floatselect @interval = (max(RandomFloat) - min(RandomFloat))/@bins, @min = min(RandomFloat), @max = max(RandomFloat)from @MyTestTable;with cteHistogram (N, StartBin, EndBin, TotalCount)as( select N, @min+(@interval*(N-1)) StartBin, @min+(@interval*N) EndBin, coalesce(count(RandomFloat), 0) TotalCount from @MyTestTable cross join Tally where RandomFloat >= @min+(@interval*(N-1)) and RandomFloat < @min+(@interval*N) and n <= @bins-1 group by N union all select N, @min+(@interval*(N-1)) StartBin, @min+(@interval*N) EndBin, coalesce(count(RandomFloat), 0) TotalCount from @MyTestTable cross join Tally where RandomFloat >= @min+(@interval*(N-1)) and RandomFloat <= @max and n = @bins group by N)select Tally.N, @min+(@interval*(Tally.N-1)) StartBin, case when Tally.N = @bins then @max else @min+(@interval*Tally.N) end EndBin, coalesce(TotalCount, 0) TotalCountfrom Tally left outer join cteHistogram on Tally.N = cteHistogram.Nwhere Tally.N <= @binsorder by Tally.N[/code]ps Im a beginner in Tally tables but have recently started using them quite a bit and absolutely love them.Im also assuming everyone has a Tally table called "Tally" or can make one easily enough.Thu, 17 Jan 2013 01:32:36 GMTmatak