Database

Session 1                                       Session 2
---------------------------------------------   -----------------------------------------------------
Select record A, field named SomeValue is 1

                                                Select record A, field named SomeValue is 1

Begin transaction

Update record A, 
   field named SomeValue is set to 2, 
   an eXclusive lock is taken

                                                Select record A, record is locked, session 2 waits

Some other modifications

                                                Session 2 still waits

Commit the transaction, lock is freed

                                                Session 2 now gets the answer, 
                                                   field named SomeValue is 2 
                                                   (the value session 1 updated)

Mycroft Holmes wrote:

If your users have SA rights using windows authentication then you cannot stop them.

dilkonika wrote:

What should i do in this case ?

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

• 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)
);