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sql group on number range, not exact number

Posted on 2012-12-22
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Last Modified: 2012-12-23
I have a column with a decimal which is a percentage .76, .24, 1.

I want to group on this column, but in .1 pt range, meaning group 0-.09, .1-.19, .2-.29.
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Question by:jackjohnson44
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Accepted Solution

by:
Steve Wales earned 333 total points
ID: 38716189
I used this as an example:

use demo
go
create table tab1 (student char(20), score decimal(9,2))

insert into tab1 values ('Fred', .74)
insert into tab1 values ('Mary', .72)
insert into tab1 values ('Ann', .69)
insert into tab1 values ('George', .62)
insert into tab1 values ('Mark', .76)
insert into tab1 values ('Bob', .54)

select round(score, 1, 1), count(*)
from tab1
group by round(score, 1, 1)

                                        
--------------------------------------- -----------
0.50                                    1
0.60                                    2
0.70                                    3

(3 row(s) affected)

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Still tweaking on making it display the range you want as a literal
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Assisted Solution

by:Qlemo
Qlemo earned 167 total points
ID: 38716192
You can group by an expression, so adding
  convert(int, percent*10)/10.0
to your group by should do. But since it is usually required to see the group itself in the output, it's better to use an in-place table:
select a,b, percent_grp, count(*)
from (
  select a, b, convert(int, percent*10)/10.0 as percent_grp
  from tbl
) x
group by a, b, percent_grp

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Expert Comment

by:Qlemo
ID: 38716197
Output as range text can be managed with
    convert(varchar(4), percent_grp) + ' - ' + convert(varchar(4), percent_grp + 0.09)
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Assisted Solution

by:Steve Wales
Steve Wales earned 333 total points
ID: 38716203
Here, this would do it and show you the range in the output.

Inner select does the grouping (and so can use indexes since you're not putting functions in the group bys and what not which might invalidate them) and then the outer select does the formatting of that output

select convert(char(4), round(score, 1, 1))+'-'+convert(char(4), round(score, 1, 1)+0.09) as score_range, total
from
(
select round(score, 1, 1) as score, count(*) as total
from tab1
group by round(score, 1, 1)
) as x
order by score_range

score_range total
----------- -----------
0.50-0.59   1
0.60-0.69   2
0.70-0.79   3

(3 row(s) affected)

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Expert Comment

by:Qlemo
ID: 38716210
sjwales,

score is now truncated twice, which does not matter for the result, but is superfluous.
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Expert Comment

by:Steve Wales
ID: 38716269
Oops!  You're right:

Joys of copy and paste :)
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