Declare @UserName VARCHAR(50),
@Msg VARCHAR(100)
IF NOT EXISTS(Select UserName From table Where UserName = @UserName)
BEGIN
INSER INTO  table values(username,Password)
END
ELSE
BEGIN
SET @Msg = 'UserName already available'
Return
END

CREATE PROCEDURE sp_NewUser            
(            
@UserId char(10),            
@Password char(10),          
@Privilege numeric(18,0),  
@MessageCode INT OUTPUT         
)            
AS            
BEGIN    
IF EXISTS(SELECT * FROM tbl_Login where UserId=@UserId)            
begin            
 SET @MessageCode = -1            
 return            
end  
INSERT INTO [tbl_Login]([UserId], [Password], [Privilege])          
VALUES(@UserId, @Password,@Privilege)          
if @@ERROR<>0            
 BEGIN            
SET @MessageCode =1      
END          
ELSE    
SET @MessageCode =0           
SET NOCOUNT OFF            
END