Deferrable unique & primary keys must use nonunique indexes. - Oracle Schema
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Q. Deferrable unique and primary keys must use nonunique indexes.
- Published on 29 Jul 15
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-Posted on 28 Sep 15
- A user sees inconsistent constraints, including duplicates in unique indexes, when that user's transaction produces these inconsistencies.
- You can place deferred unique and foreign key constraints on materialized views, allowing fast and complete refresh to complete successfully.
- Deferrable unique constraints always use nonunique indexes.
- When you remove a deferrable constraint, its index remains.
- This is convenient because the storage information remains available after you disable a constraint.
- Not-deferrable unique constraints and primary keys also use a nonunique index if the nonunique index is placed on the key columns before the constraint is enforced.
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