Question

I have a User table, which is having Userid(primary key), Username, Password

There is a stored procedure which accepts list of users as XML. My requirement is to insert the users to User table, but before inserting I need to check whether the Username is already exists. If exists then a random number should be appended with username.

How do i check whether username already exists or not and randomise it, below is the sql which blindly inserts the username. Any help?

XML Structure:<ROOT><User UserId="0" Username="ajohn" Password="548788844" ></ROOT>

SQL:

INSERT INTO [User] (Username, Password) 
        SELECT tab.col.value('@Username','nVarchar(max)') AS Username,     tab.col.value('@Password','nVarchar(max)') AS Password,            
        FROM @pupilDetails.nodes('ROOT/User') tab(col)

Answer 1

Maybe this will help:

--Existing data
DECLARE @User TABLE
(
    UserId INT PRIMARY KEY CLUSTERED IDENTITY(1,1),
    Username nVarchar(MAX),
    Password nVarchar(MAX)
)
INSERT INTO @User(Username,Password)
SELECT 'bob_456254','1584526'
UNION ALL
SELECT 'ajohn_4525846','4561584'
--Something has to separate the username and the number I used "username"_"randomnumber"
--The xml
DECLARE @pupilDetails XML='<ROOT><User UserId="0" Username="ajohn" Password="548788844" ></User></ROOT>'

;WITH CTE AS
(
    SELECT
        tab.col.value('@Username','nVarchar(max)') AS Username,
        tab.col.value('@Password','nVarchar(max)') AS Password

    FROM
        @pupilDetails.nodes('ROOT/User') AS tab(col)
)
INSERT INTO @User
(
    Username,
    Password        
)
SELECT 
    CTE.Username+
    (
        CASE WHEN EXISTS
                (
                    SELECT
                        NULL
                    FROM
                        @User AS Users
                    WHERE
                        SUBSTRING(Users.Username,0,CHARINDEX('_',Users.Username))=CTE.Username
                )
            THEN '_'+CAST(ABS(CHECKSUM(NewId())) AS VARCHAR(MAX))
            ELSE ''
        END
    ) AS UserName,
    CTE.Password  
FROM 
    CTE

SELECT * FROM @User