Booleans and Boolean Operators

Booleans and Boolean Operators¶

Unlike SQL, JSON has three Boolean states: TRUE, FALSE, and JSON UNKNOWN. JSON UNKNOWN is generally a result of an error (for example, invalid data type comparison).

Note

You cannot simply test for a true or false condition, which is the natural inclination for Boolean. For example, to compare @.age for all rows against the number 18, you cannot simply test for ‘@.age <= 18’ and ‘@.age > 18’; you must account for rows where ‘(@.age > 18)’ is unknown.

TRUE and FALSE Boolean conditions are tested using ==. Unlike SQL, Booleans cannot be tested “standalone.”

Example: Assume `@.skilled` is a Boolean value.

`? (@.skilled == TRUE)` is a valid statement.

`? (@.skilled)` is an invalid statement.

UNKNOWN Boolean conditions are testing using the IS UNKNOWN operator.

Examples

: `? (@.skilled IS UNKNOWN)`is a valid statement.

`? (@.skilled == unknown)` is an invalid statement.

&&, ||, and ! are the AND, OR, and NOT operators and work against Boolean operands.

If the initial tested operand is enough to return a result, the other operand does not need to be evaluated. (For example, if operand 1 is FALSE and the operator is &&, then operand 2 can be ignored.)

&& truth table:

	TRUE	FALSE	UNKNOWN
TRUE	TRUE	FALSE	UNKNOWN
FALSE	FALSE	FALSE	FALSE
UNKNOWN	UNKNOWN	FALSE	UNKNOWN

Note

Operators can be checked in any order, so FALSE &&``error may still return an error.

|| truth table:

	TRUE	FALSE	UNKNOWN
TRUE	TRUE	TRUE	TRUE
FALSE	TRUE	FALSE	UNKNOWN
UNKNOWN	TRUE	UNKNOWN	UNKNOWN

! truth table:

!TRUE is FALSE

!FALSE is TRUE

!UNKNOWN is UNKNOWN