Database

• Use proper security definitions on the server file system. No-one but admins should be let to operate with the files. Sql Server users don't need access to files
  See: http://msdn.microsoft.com/en-us/magazine/cc982153.aspx[^]
• Use either Sql Server or Windows authenticated logins along with proper database roles to limit the statements
  See: http://msdn.microsoft.com/en-us/library/ms189121.aspx[^]
  and http://msdn.microsoft.com/en-us/library/ms187965.aspx[^]
• Use different logins for admins
• If needed, encrypt the files
  See: http://msdn.microsoft.com/en-us/library/bb934049.aspx[^]

Product
-------
- Id
- name
- category
- IsService
- nr
- value

Sell_item
---------
- Id
- product (former item_id), foreign key to Product
- quantity
- price
- value

Article 
-------
Id
Name
Category

Services
-------- 
id
name
nr
value

Sell_action
--------- 
sell_Id
other possible fields describing a single selling action

ArticlesSold
--------- 
sell_Id
article_id
amount
price

ServicesSold
--------- 
sell_Id
service_id
amount
price

create table [table] (
  id raw(32) default sys_guid(),
  ...,
  constraint pk_id primary key (id)
);

id_memberships AUTOINCREMENT PRIMARY KEY

CREATE TABLE [SAC_MEMBERSHIPS]
(
    [id_memberships] GUID NOT NULL PRIMARY KEY,
    ...