The
word NULL is a reserved word in any
SQL. As you know NULL represents
nothing, more accurately missing data or empty cell values. A comparison with NULL always returns NULL. To find out NULL values we can either have a condition with a
logical operator with two NOT operators or we can use COALESE function.
Usage
of NOT operator
It is a
wondering truth that sometimes in life, we do NOT want something. And to
satisfy this need in SQL, there is a NOT
operator provided. Just prefix this before any comparison operator and you will
get what you do NOT want. Here is the syntax.
SELECT {*|<col1>},
<col2>, <col3>…
FROM <TABLE
name>
WHERE <COLUMN
name> NOT
<OPERATOR> <another COLUMN
name OR
constant VALUE>
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