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SQL Development
Optimizing Query Performance : Understanding optimization : Optimizer phases : Predicate expressions
Predicate expressions
When the predicates of an SQL statement use the OR logical operator to combine expressions that compare the same column with a constant, the optimizer converts these expressions to a single IN predicate. The purpose of these transformations is, where possible, to combine multiple predicates into a single predicate for simpler evaluation in this and later stages.
Similarly, a LIKE predicate on an index key, where the LIKE pattern has a prefix of fixed characters, is converted to a BETWEEN predicate.