How to group names which are dependent on other columns - sql-server

Question

I have a table like below.
CREATE TABLE #Test
(
CustId INT ,
CustName VARCHAR(100) ,
CustHeading VARCHAR(100)
)
INSERT INTO #Test
SELECT '1','john carroll','Heading 1'
UNION ALL
SELECT '1','john carroll','Heading 2'
UNION ALL
SELECT '2','john c','Heading 1'
UNION ALL
SELECT '2','john c','Heading 2'
UNION ALL
SELECT '2','john c','Heading 3'
UNION ALL
SELECT '3','john lynch','Heading 1'
UNION ALL
SELECT '4','john carroll lynch','Heading 1'
UNION ALL
SELECT '4','john carroll lynch','Heading 4'
UNION ALL
SELECT '4','john carroll lynch','Heading 5'
UNION ALL
SELECT '5','john c lynch','Heading 1'
UNION ALL
SELECT '5','john c lynch','Heading 3'
UNION ALL
SELECT '6','john c l','Heading 11'
UNION ALL
SELECT '6','john c l','Heading 12'
UNION ALL
SELECT '7','john c ln','Heading 1'
UNION ALL
SELECT '7','john c ln','Heading 2'
UNION ALL
SELECT '2','john c','Heading 11'
UNION ALL
SELECT '2','john c','Heading 12'
In this, we need to group the customers who are having atleast two matching headings among them.
For example,custID :: 1,2 and 7 are having two matching CustHeading :: Header 1 and Header 2, so they are grouped.CustID :: 2 and 5 having two matching CustHeading :: Header 1 and Header 3,they also can be grouped. Please let me know how to achieve this
without using WHILE loop
Thanks in advance.

Answer 1

SELECT
DISTINCT
CASE WHEN c.num = 1 THEN a.CustId
ELSE a.[_CustId]
END ,
CASE WHEN c.num = 1 THEN a.CustName
ELSE a.[_CustName]
END ,
'M' + CAST(DENSE_RANK() OVER ( ORDER BY mx, mn ) AS VARCHAR(100)) AS gr_nbr
FROM
(
SELECT
a.CustId ,
a.CustName ,
c.CustId _CustId ,
c.CustName _CustName,
MAX(a.CustHeading) mx,
MIN(a.CustHeading) mn
FROM
#Test a
JOIN #Test c ON c.CustHeading = a.CustHeading
AND c.CustId > a.CustId
GROUP BY
a.CustId ,
a.CustName ,
c.CustId ,
c.CustName
HAVING
MAX(a.CustHeading) <> MIN(a.CustHeading)
) a
JOIN #Test b ON b.CustId = a.[_CustId]
CROSS JOIN (
SELECT
1 num
UNION ALL
SELECT
2 num
) AS c
ORDER BY
3 ,
1

Answer 2

Sorry my brain is not working today. I'm sure there is a simpler way to do this but I can think right now. This seems to work fine for me. Let me know if it needs any changes.
CREATE TABLE #Test
(
CustId INT ,
CustName VARCHAR(100) ,
CustHeading VARCHAR(100)
)
INSERT INTO #Test
SELECT '1','john carroll','Heading 1'
UNION ALL
SELECT '1','john carroll','Heading 2'
UNION ALL
SELECT '2','john c','Heading 1'
UNION ALL
SELECT '2','john c','Heading 2'
UNION ALL
SELECT '2','john c','Heading 3'
UNION ALL
SELECT '3','john lynch','Heading 1'
UNION ALL
SELECT '4','john carroll lynch','Heading 1'
UNION ALL
SELECT '4','john carroll lynch','Heading 4'
UNION ALL
SELECT '4','john carroll lynch','Heading 5'
UNION ALL
SELECT '5','john c lynch','Heading 1'
UNION ALL
SELECT '5','john c lynch','Heading 3'
UNION ALL
SELECT '6','john c l','Heading 11'
UNION ALL
SELECT '6','john c l','Heading 12'
UNION ALL
SELECT '7','john c ln','Heading 1'
UNION ALL
SELECT '7','john c ln','Heading 2'
UNION ALL
SELECT '2','john c','Heading 11'
UNION ALL
SELECT '2','john c','Heading 12';
WITH CTE_Heading
AS
(
SELECT DISTINCT custHeading
FROM #Test
),
CTE_Paired_Headings
AS
(
SELECT A.custHeading AS Head1,
B.CustHeading AS Head2
FROM CTE_Heading A
INNER JOIN CTE_Heading B
ON A.custHeading < B.custHeading
),
CTE_Matching_Cust
AS
(
SELECT A.Head1,
A.Head2,
B.CustId,
B.CustName
FROM CTE_Paired_Headings A
INNER JOIN #Test B
ON A.Head1 = B.CustHeading
OR A.Head2 = B.CustHeading
GROUP BY A.Head1,A.Head2,B.CustId,B.CustName
HAVING COUNT(*) >= 2
),
CTE_HeadingGroups
AS
(
SELECT 'M' + CAST(ROW_NUMBER() OVER (ORDER BY Head1,Head2) AS VARCHAR(5)) MatchingID,
Head1,
Head2
FROM CTE_Matching_Cust
GROUP BY Head1,Head2
HAVING COUNT(*) >= 2
)
SELECT B.CustId,
B.CustName,
A.MatchingID
FROM CTE_HeadingGroups A
INNER JOIN CTE_Matching_Cust B
ON A.Head1 = B.Head1
AND A.Head2 = B.Head2
ORDER BY 3,1
DROP TABLE #Test
Results:
CustId CustName MatchingID
-----------------------------------------------
1 john carroll M1
2 john c M1
7 john c ln M1
2 john c M2
5 john c lynch M2
2 john c M3
6 john c l M3