Creating a loop to suggest username+number - SQL Server - sql

Question

I've been trying to create a procedure to implement in user creation. The procedure is meant to see if the username is already taken, in which case it has to print an alternative username. The alternate needs to be constructed from the username+lowest number that is not already taken.
For example, if I tried "Ofek" and both "Ofek" and "Ofek1" are taken, I should receive "Ofek2".
So far this is what I have:
ALTER PROCEDURE [dbo].[SuggestUsername]
#username varchar(10)
AS
BEGIN
DECLARE #name varchar(10)
IF #username IN (SELECT User_Name FROM Players WHERE User_Name = #username)
WHILE (#name IN (SELECT User_Name FROM Players WHERE User_Name = #username))
SET #name = (CONCAT(#username, +1))
PRINT (CONCAT('Username already taken. Please choose a different one, or use: ', #name))
END
For some reason, #name comes up as empty whenever I tried running it. Is there a better way to do it? if not, what's wrong with my current code?
Thanks in advance!
edit
I've decided to give up this idea and try to implement it differently (with a count of how many times #username already appears as the additional number). Thanks for all who tried to help.

Answer 1

Since you mention that this is just "for a class" in your comment and I have time to spend because of COVID, here is a trick.
CREATE VIEW MyView
AS
SELECT ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) N
FROM (VALUES (0), (0), (0), (0), (0), (0), (0), (0), (0)) T(A) CROSS JOIN
(VALUES (0), (0), (0), (0), (0), (0), (0), (0), (0)) TT(B) CROSS JOIN
(VALUES (0), (0), (0), (0), (0), (0), (0), (0), (0)) TTT(C) CROSS JOIN
(VALUES (0), (0), (0), (0), (0), (0), (0), (0), (0)) TTTT(D);
-- 6561 number
CREATE TABLE Users
(
UserName VARCHAR(10) UNIQUE
);
INSERT Users VALUES
('Ofek'), ('Ofek1');
CREATE PROCEDURE MyProc
#UserName VARCHAR(10)
AS
BEGIN
WITH CTE(N, UN) AS
(
SELECT 0, #UserName
UNION ALL
SELECT N, CONCAT(#UserName, N)
FROM MyView
)
INSERT Users(UserName)
SELECT TOP 1 UN
FROM CTE
WHERE NOT EXISTS(SELECT 1 FROM Users WHERE UserName = UN)
ORDER BY N;
END
EXEC MyProc 'Ofek';
SELECT * FROM Users;
You can see how it's working on a db<>fiddle
I won't recommend this as a real solution or a way to work with on a real database, instead you can add a UNIQUE constraint or using EXISTS() to notify the user if the name is already taken without suggesting.