How to add a dash between running numbers and comma between non-running numbers - tsql

Question

I would like to replace a set of running and non running numbers with commas and hyphens where appropriate.
Using STUFF & XML PATH I was able to accomplish some of what I want by getting something like 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 15, 19, 20, 21, 22, 24.
WITH CTE AS (
SELECT DISTINCT t1.ORDERNo, t1.Part, t2.LineNum
FROM [DBName].[DBA].Table1 t1
JOIN Table2 t2 ON t2.Part = t1.Part
WHERE t1.ORDERNo = 'AB12345')
SELECT c1.ORDERNo, c1.Part, STUFF((SELECT ', ' + CAST(LineNum AS VARCHAR(5))
FROM CTE c2
WHERE c2.ORDERNo= c1.ORDERNo
FOR XML PATH('')), 1, 2, '') AS [LineNums]
FROM CTE c1
GROUP BY c1.ORDERNo, c1.Part
Here is some sample output:
ORDERNo Part LineNums
ON5650 PT01-0181 5, 6, 7, 8, 12
ON5652 PT01-0181 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 15, 19, 20, 21, 22, 24
ON5654 PT01-0181 1, 4
ON5656 PT01-0181 1, 2, 4
ON5730 PT01-0181 1, 2
ON5253 PT16-3934 1, 2, 3, 4, 5
ON1723 PT02-0585 1, 2, 3, 6, 8, 9, 10
Would like to have:
OrderNo Part LineNums
ON5650 PT01-0181 5-8, 12
ON5652 PT01-0181 1-10, 13, 15, 19-22, 24
ON5654 PT01-0181 1, 4
ON5656 PT01-0181 1-2, 4
ON5730 PT01-0181 1-2
ON5253 PT16-3934 1-5
ON1723 PT02-0585 1-3, 6, 8-10

Answer 1

This is a classic gaps-and-islands problem.
(a good read on the subject is Itzik Ben-Gan's Gaps and islands from SQL Server MVP Deep Dives)
The idea is that you first need to identify the groups of consecutive numbers. Once you've done that, the rest is easy.
First, create and populate sample table (Please save us this step in your future questions):
DECLARE #T AS TABLE
(
N int
);
INSERT INTO #T VALUES
(1), (2), (3), (4),
(6),
(8),
(10), (11),
(13), (14), (15),
(17),
(19), (20), (21),
(25);
Then, use a common table expression to identify the groups.
With Grouped AS
(
SELECT N,
N - ROW_NUMBER() OVER(ORDER BY N) As Grp
FROM #T
)
The result if this cte is this:
N Grp
1 0
2 0
3 0
4 0
6 1
8 2
10 3
11 3
13 4
14 4
15 4
17 5
19 6
20 6
21 6
25 9
As you can see, while the numbers are consecutive, the grp value stays the same.
When a row has a number that isn't consecutive with the previous number, the grp value changes.
Then you select from that cte, using a case expression to either select a single number (if it's the only one in it's group) or the start and end of the group, separated by a dash:
SELECT STUFF(
(
SELECT ', ' +
CASE WHEN MIN(N) = MAX(N) THEN CAST(MIN(N) as varchar(11))
ELSE CAST(MIN(N) as varchar(11)) +'-' + CAST(MAX(N) as varchar(11))
END
FROM Grouped
GROUP BY grp
FOR XML PATH('')
), 1, 2, '') As GapsAndIslands
The result:
GapsAndIslands
1-4, 6, 8, 10-11, 13-15, 17, 19-21, 25

Answer 2

For fun I put together another way using Window Aggregates (e.g. SUM() OVER ...). I also use some newer T-SQL functionality such as CONCAT (2012+) and STRING_AGG (2017+). This using Zohar's sample data.
DECLARE #T AS TABLE(N INT PRIMARY KEY CLUSTERED);
INSERT INTO #T VALUES (1),(2),(3),(4),(6),(8),(10),(11),(13),(14),(15),(17),(19),(20),(21),(25);
WITH
a AS (
SELECT t.N,isNewGroup = SIGN(t.N-LAG(t.N,1,t.N-1) OVER (ORDER BY t.N)-1)
FROM #t AS t),
b AS (
SELECT a.N, GroupNbr = SUM(a.isNewGroup) OVER (ORDER BY a.N)
FROM a),
c AS (
SELECT b.GroupNbr,
txt = CONCAT(MIN(b.N), REPLICATE(CONCAT('-',MAX(b.N)), SIGN(MAX(b.N)-MIN(b.N))))
FROM b
GROUP BY b.GroupNbr)
SELECT STRING_AGG(c.txt,', ') WITHIN GROUP (ORDER BY c.GroupNbr) AS Islands
FROM c;
Returns:
Islands
1-4, 6 , 8, 10-11, 13-15, 17, 19-21, 25

Answer 3

And here an approach using a recursive CTE.
DECLARE #T AS TABLE(N INT PRIMARY KEY CLUSTERED);
INSERT INTO #T VALUES (1),(2),(3),(4),(6),(8),(10),(11),(13),(14),(15),(17),(19),(20),(21),(25);
WITH Numbered AS
(
SELECT N, ROW_NUMBER() OVER(ORDER BY N) AS RowIndex FROM #T
)
,recCTE AS
(
SELECT N
,RowIndex
,CAST(N AS VARCHAR(MAX)) AS OutputString
,(SELECT MAX(n2.RowIndex) FROM Numbered n2) AS MaxRowIndex
FROM Numbered WHERE RowIndex=1
UNION ALL
SELECT n.N
,n.RowIndex
,CASE WHEN A.TheEnd =1 THEN CONCAT(r.OutputString,CASE WHEN IsIsland=1 THEN '-' ELSE ',' END, n.N)
WHEN A.IsIsland=1 AND A.IsWithin=0 THEN CONCAT(r.OutputString,'-')
WHEN A.IsIsland=1 AND A.IsWithin=1 THEN r.OutputString
WHEN A.IsIsland=0 AND A.IsWithin=1 THEN CONCAT(r.OutputString,r.N,',',n.N)
ELSE CONCAT(r.OutputString,',',n.N)
END
,r.MaxRowIndex
FROM Numbered n
INNER JOIN recCTE r ON n.RowIndex=r.RowIndex+1
CROSS APPLY(SELECT CASE WHEN n.N-r.N=1 THEN 1 ELSE 0 END AS IsIsland
,CASE WHEN RIGHT(r.OutputString,1)='-' THEN 1 ELSE 0 END AS IsWithin
,CASE WHEN n.RowIndex=r.MaxRowIndex THEN 1 ELSE 0 END AS TheEnd) A
)
SELECT TOP 1 OutputString FROM recCTE ORDER BY RowIndex DESC;
The idea in short:
First we create a numbered set.
The recursive CTE will use the row's index to pick the next row, thus iterating through the set row-by-row
The APPLY determines three BIT values:
Is the distance to the previous value 1, then we are on the island, otherwise not
Is the last character of the growing output string a hyphen, then we are waiting for the end of an island, otherwise not.
...and if we've reached the end
The CASE deals with this four-field-matrix:
First we deal with the end to avoid a trailing hyphen at the end
Reaching an island we add a hyphen
Staying on the island we just continue
Reaching the end of an island we add the last number, a comma and start a new island
any other case will just add a comma and start a new island.
Hint: You can read island as group or section, while the commas mark the gaps.

Answer 4

Combining what I already had and using Zohar Peled's code I was finally able to figure out a solution:
WITH cteLineNums AS (
SELECT TOP 100 PERCENT t1.OrderNo, t1.Part, t2.LineNum
, (t2.line_number - ROW_NUMBER() OVER(PARTITION BY t1.OrderNo, t1.Part ORDER BY t1.OrderNo, t1.Part, t2.LineNum)) AS RowSeq
FROM [DBName].[DBA].Table1 t1
JOIN Table2 t2 ON t2.Part = t1.Part
WHERE t1.OrderNo = 'AB12345')
GROUP BY t1.OrderNo, t1.Part, t2.LineNum
ORDER BY t1.OrderNo, t1.Part, t2.LineNum)
SELECT OrderNo, Part
, STUFF((SELECT ', ' +
CASE WHEN MIN(line_number) = MAX(line_number) THEN CAST(MIN(line_number) AS VARCHAR(3))
WHEN MIN(line_number) = (MAX(line_number)-1) THEN CAST(MIN(line_number) AS VARCHAR(3)) + ', ' + CAST(MAX(line_number) AS VARCHAR(3))
ELSE CAST(MIN(line_number) AS VARCHAR(3)) + '-' + CAST(MAX(line_number) AS VARCHAR(3))
END
FROM cteLineNums c1
WHERE c1.OrderNo = c2.OrderNo
AND c1.Part = c2.Part
GROUP BY OrderNo, Part
ORDER BY OrderNo, Part
FOR XML PATH('')), 1, 2, '') AS [LineNums]
FROM cteLineNums c2
GROUP BY OrderNo, Part
I used the ROW_NUMBER() OVER PARTITION BY since I returned multiple records with different Order Numbers and Part Numbers. All this lead to me still having to do the self join in the second part in order to get the correct LineNums to show for each record.
The second WHEN in the CASE statement is due to the code defaulting to having something like 2, 5, 8-9, 14 displayed when it should be 2, 5, 8, 9, 14.