SQL: Records showing blank during the execution of a query

I am executing a query

Select * 
from Parking 
Where ParkingStartTime <> '08:00:00.0000000' 
  AND ParkingStartTime IS NULL

In return to the execution, the columns names a开发者_如何学Cre displayed but there records are not showing.

If I used OR Rather than AND it works. Any idea of why AND is not working?

Regards.

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This can never return any results. The 2 conditions are contradictory.

If ParkingStartTime IS NULL then ParkingStartTime <> '08:00:00.0000000' will evaluate to unknown.

True and Unknown evaluates to Unknown under the truth tables for 3 valued logic.

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If ParkingStartTime is null, it can't have a value. This means that any value that meets the first part of the query cannot meet the second part of the query.

You either need just

ParkingStartTime is null

or

ParkingStartTime <> '08:00:00.000000'

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ParkingStartTime cannot be both NULL (unknown) and also be equal to a particular value e.g. 08:00:00.0000000

The query does not return any values because your logic is incorrect.