PRIMARY KEY or UNIQUE constraint When you create a PRIMARY KEY constraint, a unique clustered index on the column or columns is automatically created if a clustered index on the table does not already exist and you do not specify a unique nonclustered index.vor 5 Tagen
Is a unique key an index?
Unique keys are indexes. If your values are guaranteed to be unique, this is the best choice. Unique Key: Unique Key enforces uniqueness of the column on which they are defined. Unique Key creates a non-clustered index on the column.
Does unique key create index SQL Server?
We know that the unique constraint in SQL Server creates a unique SQL Server index as well. SQL Server allows us to disable an index as well without dropping it.
Do I need an index if I have a unique constraint?
Under the hood a unique constraint is implemented the same way as a unique index – an index is needed to efficiently fulfill the requirement to enforce the constraint.