With the ALL search condition, if the value of subquery result set is the empty set, the search condition evaluates to TRUE.
Otherwise, the search condition evaluates to TRUE, FALSE, or UNKNOWN, depending on the value of expression, and the result set returned by the subquery, as follows:
If the expression value is...
and the result set returned by the subquery contains at least one NULL, then...
or the result set returned by the subquery contains no NULLs, then...
NULL
UNKNOWN
UNKNOWN
not NULL
If there exists at least one value in the subquery result set for which the comparison with the expression value is FALSE,
then the search condition evaluates to FALSE. Otherwise, the search condition evaluates to UNKNOWN.
If there exists at least one value in the subquery result set for which the comparison with the expression value is FALSE,
then the search condition evaluates to FALSE. Otherwise, the search condition evaluates to TRUE.
Syntax