A predicate specifies a condition that is
true, false, or unknown about a given value, row, or group.
The following rules apply to all types of predicates:
- All values specified in a predicate must be compatible.
- An expression used in a basic, quantified, IN, or BETWEEN predicate
must not result in a character string with a length attribute greater
than 4000, a graphic string with a length attribute greater than 2000,
or a LOB string of any size.
- The value of a host variable can be null (that is, the variable
may have a negative indicator variable).
- The code page conversion of operands of predicates involving two
or more operands, with the exception of LIKE, is done according to
the rules for string conversions.
- Use of a structured type value is limited to the NULL predicate
and the TYPE predicate.
- In a Unicode database, all predicates that accept a character
or graphic string will accept any string type for which conversion
is supported.
A fullselect is a form of the SELECT statement that, when
used in a predicate, is also called a subquery.
Row-value-expression
The
operand of several predicates (basic, quantified, and IN) can be expressed
as a row value expression:
row-value-expression
.-,----------.
V |
|--(----expression-+--)-----------------------------------------|
A row value expression returns a single row that
consists of one or more fields. The field values can be specified
as a list of expressions. The number of fields that are returned by
the row value expression is equal to the number of expressions that
are specified in the list.
DB2 Version 9.7 for Linux, UNIX, and Windows