SQL Server Loop thru rows to form Groups - sql

Question

I using SQL Server 2008 R2 / 2014. I wish to find a SQL query that can do the following:
Rules:
Each [Group] must have [Number] 1 to 6 to be complete group.
[Name] in each [Group] must be unique.
Each row only can use 1 time.
Table before sorting is...
Name Number Group
---- ------ -----
A 1
B 6
A 123
C 3
B 4
C 23
D 45
D 4
C 56
A 12
D 56
After sorting, result I want is below or similar....
Name Number Group
---- ------ -----
A 1 1
C 23 1
D 45 1
B 6 1
A 123 2
D 4 2
C 56 2
A 12 3
C 3 3
B 4 3
D 56 3
What I tried before is to find a subgroup that have [Number] consist of 1-6 with below concatenate method...
SELECT *
FROM [Table1] ST2
WHERE
SUBSTRING((SELECT ST1.[Number] AS [text()]
FROM [Table1] ST1
-- WHERE ST1.[Group] = ST2.[Group]
ORDER BY LEFT(ST1.[Number],1)
FOR XML PATH ('')), 1, 1000) = '123456'

Answer 1

Maybe you should check ROW_NUMBER function.
select Name
, Number
, ROW_NUMBER () OVER(PARTITION BY Name ORDER BY Number) as Group
from [Table1]
If you have more than 6 rows with same NAME value then it will return more groups. You can filter additional groups out since you are interested in only 6 groups with unique values of NAME column.

Answer 2

I'm not sure if this can be done more simply or not, but here's my go at it...
Advanced warning, this requires some means of splitting strings. Since you're not on 2016, I've included a function at the beginning of the script.
The bulk of the work is a recursive CTE that builds the Name and Number columns into comma delimited groups. We then reduce our working set to only the groups where the numbers would create 123456, split the groups and use ROW_NUMBER() OVER... to identify them, and then select based on the new data.
Demo: http://rextester.com/NEXG53500
CREATE FUNCTION [dbo].[SplitStrings]
(
#List NVARCHAR(MAX),
#Delimiter NVARCHAR(255)
)
RETURNS TABLE
WITH SCHEMABINDING
AS
RETURN
(
SELECT Item = y.i.value('(./text())[1]', 'nvarchar(4000)')
FROM
(
SELECT x = CONVERT(XML, '<i>'
+ REPLACE(#List, #Delimiter, '</i><i>')
+ '</i>').query('.')
) AS a CROSS APPLY x.nodes('i') AS y(i)
);
GO
CREATE TABLE #temp
(
name VARCHAR(MAX),
number INT
)
INSERT INTO #temp
VALUES
('a',1),
('b',6),
('a',123),
('c',3),
('b',4),
('c',23),
('d',45),
('d',4),
('c',56),
('a',12),
('d',56);
/*** Recursively build groups based on information from #temp ***/
WITH groupFinder AS
(
SELECT CAST(name AS VARCHAR(MAX)) AS [groupNames], CAST(number AS VARCHAR(max)) AS [groupNumbers] FROM #temp
UNION ALL
SELECT
cast(CONCAT(t.[Name],',',g.[groupNames]) as VARCHAR(MAX)),
CAST(CONCAT(CAST(t.[Number] AS VARCHAR(max)),',',CAST(g.[groupNumbers] AS VARCHAR(max))) AS VARCHAR(max))
FROM #temp t
JOIN groupFinder g
ON
g.groupNames NOT LIKE '%' + t.name+'%'
AND g.[groupNumbers] NOT LIKE '%' + CAST(t.number/100 AS VARCHAR(10)) +'%'
AND g.[groupNumbers] NOT LIKE '%' + CAST(t.number/10 AS VARCHAR(10)) +'%'
AND g.[groupNumbers] NOT LIKE '%' + CAST(t.number%10 AS VARCHAR(10)) +'%'
)
/*** only get groups where the numbers form 123456 ***/
, groupPruner AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY [groupNames]) AS [rn] FROM groupFinder WHERE REPLACE([groupNumbers],',','') = '123456'
)
/*** split the name group and give it identifiers ***/
, nameIdentifier AS
(
SELECT g.*, c1.[item] AS [Name], ROW_NUMBER() OVER (PARTITION BY [rn] ORDER BY (SELECT NULL)) AS [rn1]
FROM groupPruner g
CROSS APPLY splitstrings(g.groupnames,',') c1
)
/*** split the number group and give it identifiers ***/
, numberIdentifier AS
(
SELECT g.*, c1.[item] AS [Number], ROW_NUMBER() OVER (PARTITION BY [rn], [rn1] ORDER BY (SELECT NULL)) AS [rn2]
FROM nameIdentifier g
CROSS APPLY splitstrings(g.groupNumbers,',') c1
)
SELECT [Name], [Number], [rn] AS [Group]
--,groupnames, groupNumbers /*uncomment this line to see the groups that were built*/
FROM numberIdentifier
WHERE rn1 = rn2
ORDER BY rn, rn1
DROP TABLE #temp