How to get distinct value

CREATE TABLE yourtable
	([ID] int, [User] varchar(10), [Department] varchar(8))
;
	
INSERT INTO yourtable
	([ID], [User], [Department])
VALUES
	(1, 'User1', 'Admin'),
	(2, 'User1', 'Accounts'),
	(3, '1User2', 'Finance'),
	(4, 'User3', 'Sales'),
	(5, '123User3', 'Finance')
;

select distinct REPLACE(REPLACE(REPLACE(t.[user], '1', ''), '2', ''), '3', '')
from yourtable t;

internal static class Program
{
    private static void Main()
    {
        var list = new List<string>() {
            "Kumar",
            "Kumar1",
            "Kumar2",
            "123Kumar",
            "2Kumar1",
            "Muruga1",
            "Muruga2",
            "123Muruga",
            "1Muruga3"
        };

        foreach (var result in list.Select(x => GetLongestMatch(x, list.Except(new List<string> { x }))).Distinct())
            Console.WriteLine($"{result.Key} was found {result.Value} time{(result.Value > 1 ? "s" : "")}");

        Console.WriteLine("-- done --");
        Console.ReadKey();
    }

    private static KeyValuePair<string, int> GetLongestMatch(string item, IEnumerable<string> list)
    {
        var results = new Dictionary<string, int>();
        foreach (string subStr in GetAllSubstrings(item).OrderByDescending(s => s.Length))
            results.Add(subStr, list.Count(s => s.Contains(subStr)) + 1);

        return results.OrderByDescending(x => x.Value).FirstOrDefault();
    }

    public static IEnumerable<string> GetAllSubstrings(string word)
        => from ndx1 in Enumerable.Range(0, word.Length)
            from ndx2 in Enumerable.Range(0, word.Length - ndx1 + 1)
            where ndx2 >= 2
            select word.Substring(ndx1, ndx2);
}

Kumar was found 5 times
Muruga was found 4 times
-- done --