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Can we compare Null with null?
The result of comparing anything to NULL , even itself, is always, always NULL . A comparison to NULL is never true or false. Since NULL can never be equal to any value, it can never be unequal, either. Sometimes people have difficulty understanding why a comparison to NULL can never be either true or false.
How do you compare variables with null?
To check for null variables, you can use a strict equality operator ( === ) to compare the variable with null . This is demonstrated below, where the boolean expression evaluates to true for only for null and evaluates to false for other falsy values.
Can we compare null to null in SQL?
In SQL null is not equal ( = ) to anything—not even to another null . According to the three-valued logic of SQL, the result of null = null is not true but unknown. With is [not] distinct from SQL also provides a comparison operator that treats two null values as the same.
What makes a variable null?
NULL is a special variable of type Undefined. Unlike a variable that is truly undefined, the value ! NULL can be assigned to other variables and used in comparisons.
How can I compare null values-Ask Tom?
Another ‘benefit’ of using DUMP to compare values is that if the datatype is different, the match fails, so you are compelled to do explicit datatype conversion. Realised that DUMP does return a NULL. I’ve just got my own function replaceing itthat does an NVL (DUMP (…),’NULL’).
How to compare values which are both null in T-SQL?
The idea is to use short circuit in predicates to make sure the equal operator (=) is used only with non-null values, otherwise null would propagate up in the expression tree. You could use SET ANSI_NULLS in order to specify the behavior of the Equals (=) and Not Equal To (<>) comparison operators when they are used with null values.
Can a null value be replaced by 0?
My solution (might be useful for someone looking here) is to do the comparison normal, with null values replaced not by 0, but the maximum value possible (e.g. Integer.MAX_VALUE). Returning 0 is not consistent, if you have values that are themselves 0. Here a correct example:
Why does Java comparator return 0 for NULL values?
However from time to time an address without coordinates is in the list causing a NullPointerException. My initial idea to fix this was to have the comparator return 0 as distance for addresses where at least one of the coordinates is null. I fear this might lead to corruption of the order the ‘valid’ elements in the list.