Atomics can be compared with the usual six comparison operators (equality, non-equality, lower-than, greater-than, lower-or-equal, greater-or-equal), and with the same two-letter symbols as in MongoDB.
Comparison is only possible between two compatible types, otherwise, an error is raised.
Example 8.8. Equality comparison.
1 + 1 eq 2,
1 lt 2
Results:
true
true
null can be compared for equality or inequality to anything - it is only equal to itself so that false is returned when comparing if for equality with any non-null atomic. True is returned when comparing it with non-equality with any non-null atomic.
Example 8.9. Equality and non-equality comparison with null.
1 eq null,
"foo" ne null,
null eq null
Results:
false
true
true
For ordering operators (lt, le, gt, ge), null is considered the smallest possible value (like in JavaScript).
Example 8.10. Ordering comparison with null.
Comparisons and logic operators are fundamental for a query language and for the implementation of a query processor as they impact query optimization greatly. The current comparison semantics for them is carefully chosen to have the right characteristics as to enable optimization.
