Unique key
A unique key constrains values or combinations so they cannot occur more than once within the defined data scope.
Choose the right uniqueness boundary
A unique key or corresponding uniqueness constraint prevents duplicate values in selected columns or their combination. In a fictional example, the combination of tenant, an isolated customer context, and product code must be unique. The same code may then occur in a different tenant, but not again within the same tenant.
Choosing the right boundary matters. Clarify comparison rules such as case sensitivity and the treatment of missing values (NULL). These depend on database-system behaviour and settings. Technical uniqueness does not prove that different records cannot describe the same real company. It therefore replaces neither business duplicate review nor access control.
Sources
Related terms
- SKUA SKU identifies an internal product or variant. Two pack sizes show why the correct match matters for ordering.
- Multi-tenancyMulti-tenancy supports separate customer or group scopes in one solution. A tenant is not automatically one person or one database.
- Foreign keyA foreign key protects a defined reference between records through matching key values.
- Legacy systemAn existing system still in use, with technical and business dependencies accumulated over time.
- Browser cacheThe browser cache stores suitable HTTP responses for later use. Reuse and revalidation follow the applicable rules.
- Cache invalidationCache invalidation ends reuse of a stored copy under defined rules. The source record remains a separate concern.
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