Equality conditions are search conditions with a comparison predicate, to which the following rules apply:
· The only operator is the relational operator =.
·
Equality
conditions have one of the following forms:
<column_spec> = <extended_value_spec>
<column_spec> = <subquery>
The Optimizer can use only equality conditions that satisfy these prerequisites to determine an optimal search strategy.
Conditions in the format ...NOT (<column_spec> <> <extended_value_spec>) or ...NOT (<column_spec> <> <subquery>) are, where possible, converted into an expression without NOT, with a correspondingly negated operator =. The system then continues processing the condition in this converted format.