IF NOT EXISTS(SELECT * FROM sys.columns WHERE object_id = OBJECT_ID(N'[dbo].[KUNDEN]')
AND name = 'payment_type')
ALTER TABLE KUNDEN ADD payment_type varchar(255)  NULL

IF NOT EXISTS(SELECT * FROM sys.columns WHERE object_id = OBJECT_ID(N'[dbo].[KUNDEN]')
AND name = 'payment_id')
ALTER TABLE KUNDEN ADD payment_id varchar(255)  NULL