DBMS automatically creates unique index on primary key column - Database

Q.  When a primary key is define in the table, DBMS automatically creates a ____ on a primary key column.
- Published on 19 Oct 15

a. Unique index
b. Sequence
c. Trigger
d. Synonym

ANSWER: Unique index

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    Discussion

  • Nirja Shah   -Posted on 29 Oct 15
    - Indexes play an important role in DBMS for the implementation of primary keys.

    - When you define a table's primary key, the DBMS automatically creates a unique index on the primary key column you declared.

    - In a unique index as its name implies, the index key can have only one pointer value (row) associated with it.

    - Indexes can be unique or non-unique.

    - Unique indexes guarantee that no two rows of a table have duplicate values in the key column (or columns).

    - Non-unique indexes do not impose this restriction on the column values.

    - Use the CREATE UNIQUE INDEX statement to create a unique index.

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