Converting two Text/Numerical data to Ranges - sql-server-2008-r2

Question

I'm attempting to convert data from two columns (one with text and one with numbers) to a range.
I've searched and unable to find something that works for this needed solution:
Table:
ColumnA Nvarchar(50)
ColumnB Int
Table Sample:
ColumnA ColumnB
AA 1
AA 2
AA 3
AA 4
AA 5
AB 1
AB 2
AB 3
AB 4
Desired Output:
AA:1-5, AB:1-4
Any help would be greatly appreciated

Answer 1

Note I am assuming the reason you're asking the question is that you can have broken ranges and you're not simply looking for the min/max ColumnB for each ColumnA.
If you ask me, this type of thing is probably best handled in code on either an intermediate layer or directly in your presentation layer. Sort the rows by (ColumnA, ColumnB) in your query, then you can get the desired results in a single pass as you read rows - by comparing the current values with the previous row, and outputting a row when either ColumnA changes or ColumnB is not adjacent.
However, if you're bent on doing this in SQL, you can use a recursive CTE. The basic premise would be to correlate each row with an adjacent row and hold on to the beginning value of ColumnB as you proceed. An adjacent row is defined as a row with the same value of ColumnA and the next value of ColumnB (i.e. the previous row + 1).
Something like the following ought to do:
;with cte as (
select a.ColumnA, a.ColumnB, a.ColumnB as rangeStart
from myTable a
where not exists ( --make sure we don't keep 'intermediate rows' as start rows
select 1
from myTable b
where b.ColumnA = a.ColumnA
and b.ColumnB = a.ColumnB - 1
)
union all
select a.ColumnA, b.ColumnB, a.rangeStart
from cte a
join myTable b on a.ColumnA = b.ColumnA
and b.ColumnB = a.ColumnB + 1 --correlate with 'next' row
)
select ColumnA, rangeStart, max(ColumnB) as rangeEnd
from cte
group by ColumnA, rangeStart
And given your sample data, indeed it does.
And for kicks, here is another Fiddle with data having gaps in ColumnB.

Answer 2

Note the group by clause for the continuous values by doing some math.
DECLARE #Data table (ColumnA Nvarchar(50), ColumnB Int)
INSERT #Data VALUES
('AA', 1),
('AA', 2),
('AA', 3),
--('AA', 4),
('AA', 5),
('AB', 1),
('AB', 2),
('AB', 3),
('AB', 4)
;WITH Ordered AS
(
SELECT
ROW_NUMBER() OVER (PARTITION BY ColumnA ORDER BY ColumnB) AS Seq,
*
FROM #Data
)
SELECT
ColumnA,
CASE
WHEN 1 = 0 THEN ''
-- if the ColumnA only has 1 row, the display is 1-1? or just 1?
--WHEN MIN(ColumnB) = MAX(ColumnB) THEN CONVERT(varchar(10), MIN(ColumnB))
ELSE CONVERT(varchar(10), MIN(ColumnB)) + '-' + CONVERT(varchar(10), MAX(ColumnB))
END AS Range
FROM Ordered
GROUP BY
ColumnA,
ColumnB - Seq -- The math
ORDER BY ColumnA, MIN(ColumnB)
SQL Fiddle