This example replaces null with an empty string in SomeTable.SomeColum
UPDATE SomeTable SET SomeColumn = '' WHERE SomeColumn IS NULL
The important thing to note here is that the check to find the value that is NULL is based on “IS NULL” (it is not possible to use the equals sign to check for NULL)
Here is how to do a select where a column have NULL as the stored value.
SELECT * FROM SomeTable WHERE SomeColumn IS NULL
Equals sign does not work for null, trying to use the equals operator generates the result Unknown (it is not true nor false)
IF i = NULL THEN
SELECT 'Result is True'
ELSEIF NOT(i = NULL) THEN
SELECT 'Result is False'
SELECT 'Result is Unknown';
--This will end with Result is Unknown
This is based on the fact that null was introduced to represent “missing information and inapplicable information” in the database model and based on that statement using equals null was not implemented.