Interior state of object                                             
Let’s define our column order_date as an object (this is it, in fact) which number of compared operators,
negating conditions and null test are used to test single values in one SQL statement. In our case we have
8 possible states of object “order_date”.

1) for down value: <= , NOT<=                                   (2 states)
            2) for up value:       =>, NOT=>                                   (2 states)
            3) between values: BETWEEN, NOT BETWEEN       (2 states)
            4) test on NULL value: IS NULL, IS NOT NULL       (2 states)
But, there is one more now invisible state of object; it is excluding of object. Add this state to active states of object.
            5) state of excluding of object.                                      (1 state)
We have 9 possible states for object mentioned above.

 Photo description and image                        
Our user was on vacation last summer, and from that vacation he had wonderful memories. Very often, in free time,
he has described to his colleagues the place where he had spent his summer days. Beautiful place with narrow,
stone paved streets. Old houses with small wooden windows, from which deepness, sometimes, nice kitchen smell
and restless laughing of children had reached out. One day, our user came with his summer photos.
Sometimes, they could tell more than words.
Therefore, let’s try to transform our cruel word of SQL sentences into something else to be closer to our user.
We want to show 9 states of object “order_date”. But, we will exclude state of test on null value.

     What we must have:
            1) entry of down value
            2) entry of up value

       We ought to have switches in order to know which value is active.
            1) the switch for down value activity
            2) the switch for up value activity