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Nulls and Comparisons
Because a null is not a value, it cannot be compared to any other value (including another null value). For example, the following where clause evaluates to "false" if one or both of the columns is null:
where  columna  =  columnb
Similarly, the where clause
where  columna  <  10  or  columna  >=  10
is true for all numeric values of "columna", but false if "columna" is null.
Last modified date: 06/08/2023