Hi,

> Unique constraint creates unique index, but it is possible to achieve
> the same creating manually unique index. What is the difference
> between unique index and unique constraint?

Unique indices cannot be used in referential integrity constraints.

Indices are a physical implementation thing, while constraints are
a conceptual relational theory thing.

Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Oracle &
MS SQL Server
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