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DB_E_DUPLICATECONSTRAINTID
Meaning
Windows documents DB_E_DUPLICATECONSTRAINTID as “Constraint already exists”. In this case, constraint creation requests an ID that already names a constraint in the target scope.
Relevant contract
OLE DB DDL interfaces identify indexes, commands and constraints with provider-scoped DBIDs. Constraint descriptors also carry type, column arrays, match behavior, deferrability and update/delete rules that must agree as one structure.
Investigation of this result should start with the session performing DDL, target table metadata and the exact DBID or DBCONSTRAINTDESC supplied.
Evidence to collect
When recording diagnostic data involving catalog names, schema names, object identifiers and deployment definitions, use types, lengths, hashes or redacted identifiers rather than secrets or complete business data.
- Evidence 1: constraint DBID and target table.
- Evidence 2: existing constraint definition.
- Evidence 3: migration transaction and deployment version.
Conditions that specifically lead to it
- Cause 1: the migration is being applied twice.
- Cause 2: generated constraint names collide.
- Cause 3: a previous failed deployment committed the constraint before reporting failure.
Diagnostic sequence
- Identify the exact failing stage: constraint creation requests an ID that already names a constraint in the target scope.
Retry and recovery
Retry rule: retry with a unique ID or treat an equivalent existing constraint according to an explicit idempotency policy.
Corrective actions
- Action 1: make migrations detect equivalent existing constraints.
- Action 2: generate collision-safe deterministic names.
- Action 3: remove or rename only after verifying dependency impact.
Practical scenario
A deployment reruns after losing its response and finds the constraint already present; comparing definitions avoids creating a duplicate.
Difference from nearby HRESULT values
DB_E_BADCONSTRAINTID means the ID is invalid, while DB_E_DUPLICATECONSTRAINTID means a valid ID is already in use.
Official Microsoft references
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