Equality conditions are search conditions with a comparison predicate. The following applies to equality conditions:
· The only operator is the relational operator =.
·
They
have one of the following forms:
<column_spec> =
<extended_value_spec>
<column_spec> = <subquery>
The equality condition must have one of these forms before the Optimizer can use it to determine a search strategy. If the equality condition has another form, the Optimizer attempts to change it.
Expressions with the following forms are changed to conditions without NOT, with the appropriate negated operator =:
...NOT (<column_spec> <> <extended_value_spec>)
...NOT (<column_spec> <> <subquery>)
The Optimizer then continues to process the modified condition.