By specifying a quantified predicate (quantified_predicate), you can compare a value or list of values to a set of values or value lists.
<quantified_predicate> ::=
<expression>
<comp_op> <quantifier> <expression_list>
| <expression> <comp_op>
<quantifier> <subquery>
| <expression_list> <equal_or_not> <quantifier> (<expression_list>,...)
| <expression_list> <equal_or_not> <quantifier> <subquery>
The following
comparison operators are available to compare values:
<comp_op> ::= < | > |
<> | != | = | <= | >=
| ~= | ~< |
~> (for computers with ASCII code)
Value lists can
only be compared using the following operators: <equal_or_not> ::= <> |=
| ~| ~= | ~< |
~> (for computers with ASCII code)
The quantified predicate can be qualified with ALL, SOME, or ANY.
<quantifier> ::= ALL | SOME | ANY
The subquery (subquery) must supply a result table that contains the same number of columns as the number of values specified by the expression or expression list on the left-hand side of the operator.
Each list of values specified to the right of the equal_or_notoperator expression_list must contain the same number of values as specified in the value list in front of the equal_or_notoperator.
· Let x be the result of the first expression and S the result of the subquery or sequence of values. S is a set of values s. The value x and the values in S must be comparable with each other.
·
If a value list
(expression_list) is specified on the left of the comparison
operator equal_or_not, then let x be the value list comprising the
results of the values x1, x2, ..., xn of this value list. Let S be the
result of the subquery consisting of a set of
value lists s or a sequence of value lists s. A value list s consists of the
results of the values s1, s2, ..., sn. A value xm must be comparable with all values sm.
x=s is true if xm=sm,
m=1,...,n
x<>s is true if there is at least one m for which xm<>sm
x <equal or not> s is undefined if there is no m for which xm <equal or not> sm is false and if
there is at least one m for which xm <equal_or_not> sm is undefined.
If one xm or one ym is
a NULL value, or if the result of the subquery is
empty, x <equal_or_not> y is undefined.
The entry '------' in the list below means that no statement can be made if only the result of the comparison with one s is known.
x <compare> <quantifier> S, whereby compare ::= comp_op | equal_or_not
|
quantifier ::= ALL |
quantifier ::= ANY | SOME |
S is empty |
True |
False |
x <compare> S is true for at least one s from S |
------ |
True |
x <compare> S is true for all s from S |
True |
True |
x <compare> S is not false for any value from S and is undefined for at least one value s |
Undefined |
|
S contains NULL values and x <compare> S is true for all other s |
Undefined |
True |
x <compare> S is false for at least one value s from S |
False |
------ |
x <compare> S is false for all s from S |
False |
False |
x <compare> S is not true for any value s from S and is undefined for at least one value s |
|
Undefined |
S contains NULL values and x <compare> S is false for all other s |
False |
Undefined |