Handling duplicate values in update query with UQ column - sql-server

Question

I am migrating user information from few source databases and generating Usernames in destination to those users that are compiled in two ways: 1. If user does not belong to 'usergroup' username is lastname+runningnumber(for duplicates) 2. if they belong to usergroup their username is usergroup+runningnumber. RunningNumber should not be 'universal' across all users, but instead limited to duplicates f.ex
User1,User2,User3,UserGroup1,UserGroup2,UserGroup3
It was suggested to me that this will be simpler to achieve outside of SSIS.
When running the query duplicate values might exists already in dest.db or they might be generated via query.
This is my current query (not working properly) and I need some help in approaching this issue:
SET XACT_ABORT OFF ;
BEGIN
DECLARE #Any_error int;
WITH Kep as (SELECT Id, CASE WHEN UserGroup IS NULL THEN CAST(LEFT(LOWER(REPLACE(LastName, ' ','')), 10) +'-'+
RIGHT(CAST(ROW_NUMBER() OVER(PARTITION BY LEFT(LOWER(REPLACE(LastName, ' ','')), 10) ORDER BY LastName) as nvarchar(50)),4) AS nvarchar(50)) ELSE CAST(LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10) +'-'+
RIGHT(+CAST(ROW_NUMBER() OVER(PARTITION BY LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10) ORDER BY UserGroup) as nvarchar(50)),4) AS nvarchar(50)) END AS rn
FROM Users)
UPDATE TOP(1000) Users
SET UserName = rn
SELECT #Any_error = ##ERROR
IF #Any_error = 2627 GOTO ErrorHandler
ErrorHandler:
DECLARE #RunningNumber INT
SET #RunningNumber = 1
Loop:
BEGIN
WHILE (#Any_error = 2627)
SET #RunningNumber = #RunningNumber+1;
WITH Kep as (SELECT Id, CASE WHEN UserGroup IS NULL THEN CAST(LEFT(LOWER(REPLACE(LastName, ' ','')), 10) +'-'+
RIGHT(+CAST(ROW_NUMBER() OVER(PARTITION BY LEFT(LOWER(REPLACE(LastName, ' ','')), 10) ORDER BY LastName)+#RunningNumber as nvarchar(50)),4) AS nvarchar(50)) ELSE CAST(LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10) +'-'+
RIGHT(+CAST(ROW_NUMBER() OVER(PARTITION BY LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10) ORDER BY UserGroup)+#RunningNumber as nvarchar(50)),4) AS nvarchar(50)) END AS rn
FROM Users)
UPDATE Users
SET UserName = rn
SELECT #Any_error = ##ERROR
IF (#Any_error = 2627) GOTO Loop;
END
END
Any advice / help is highly appreciated!
EDIT: Data..
Source
LastName UserGroup
Smith Sales
Smith Sales
Smith NULL
Smith NULL
Johnson Development
Johnson NULL
Destination
LastName UserGroup Username
Smith Sales sales-1
Smith Sales sales-2
Smith NULL smith-1
Smith NULL smith-2
Johnson Development development-1
Johnson NULL johnson-1

Answer 1

Yikes, your query looks scary. Try something like this:
My Versions of Your Tables
DECLARE #yourTable TABLE (LastName VARCHAR(15),UserGroup VARCHAR(15));
INSERT INTO #yourTable
VALUES ('Smith','Sales'),
('Smith','Sales'),
('Brown','Sales'), --added this row
('Smith',NULL),
('Smith',NULL),
('Johnson','Development'),
('Johnson',NULL);
DECLARE #destinationTable TABLE (LastName VARCHAR(15),UserGroup VARCHAR(15),UserName VARCHAR(15))
INSERT INTO #destinationTable
VALUES ('Smith',NULL,'Smith-1'),
('Stevens','Sales','Sales-1'),
('Stevens','Sales','Sales-2'),
('Lopez','Development','Development-1');
Actual Query
--INSERT INTO #destinationTable
SELECT LastName,
UserGroup,
COALESCE(UserGroup,LastName)
+ '-'
+ CAST(ROW_NUMBER() OVER (PARTITION BY COALESCE(UserGroup,LastName) ORDER BY (SELECT NULL)) + COALESCE(max_num,0) AS VARCHAR(10))
AS UserName
FROM #yourTable AS A
CROSS APPLY (
SELECT MAX(CAST(SUBSTRING(UserName,CHARINDEX('-',UserName) + 1,1000) AS INT)) --finds maximum number already used in destination table
FROM #destinationTable AS B
WHERE COALESCE(A.UserGroup,A.LastName) = COALESCE(B.UserGroup,B.LastName)
) CA(max_num)
Results:
LastName UserGroup UserName
--------------- --------------- --------------------------
Johnson Development Development-2
Johnson NULL Johnson-1
Smith Sales Sales-3
Smith Sales Sales-4
Brown Sales Sales-5
Smith NULL Smith-2
Smith NULL Smith-3

Answer 2

If you have a LastName same as a UserGroup this could produce duplicates
SELECT LastName,
UserGroup,
LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10)
+ '-'
+ CAST(ROW_NUMBER() OVER (PARTITION BY LEFT(LOWER(REPLACE(UserGroup, ' ','')), 10) ORDER BY (SELECT NULL)) AS VARCHAR(10))
AS UserName
FROM Users
WHERE UserGroup is not null
SELECT LastName,
UserGroup,
LEFT(LOWER(REPLACE(LastName, ' ','')), 10)
+ '-'
+ CAST(ROW_NUMBER() OVER (PARTITION BY LEFT(LOWER(REPLACE(LastName, ' ','')), 10) ORDER BY (SELECT NULL)) AS VARCHAR(10))
AS UserName
FROM Users
WHERE UserGroup is null