Null Value:
It
is an unknown, undefined, insufficient, missing and junk values
It
is neither empty nor zero
Even
system doesn’t know what exactly the null value is Null
is not applicable in a row concept
It
will be displayed as a blank space on the screen
A special operator ‘IS NULL’ is used to handle
the null values
A
reserved word ‘NULL’ is used to assign null values
Every
null is unique
Null
values are taken higher values than number and character in order by clause
All
the arithmetic operators with null values will result in null values
Decode
function will treats the null values equal
Concatenation
operator will ignore the null values
Codes
without any space will also be treated as null value
Oracle
database allocates one byte for null value when it fall between column values
A concept of null is not applicable to row or
record
Truth Table:
AND
O R
|
T
|
F
|
NULL
|
T
|
T
T
|
F
T
|
N
T
|
F
|
F
T
|
F
F
|
F
N
|
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