Unique Constraints (Visual Database Tools)
A unique constraint ensures no duplicate values are entered into specified columns that are not a table's primary key. For example, in the employee table in which the emp_id column is the primary key, you can define a unique constraint that requires entries in the Social Security number (ssn) column to be unique within the table.
In Table Designer, you use the Indexes/Keys dialog box to create, modify, or delete unique constraints.
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Ensuring no duplicate values are entered in specific columns |
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Changing the columns that the constraint is attached to, changing the constraint name, or setting additional properties for the constraint |
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Removing the requirement for uniqueness for values entered in the column |