Index is a database object which is used to retrieve the data quickly from existing table. Indexes are classified into two types those are
If we apply any primary key Constraint or unique Constraint or any particular column on the table oracle engine internally maintains one of the index mechanisms called UNIQUE Index.
Non Unique index
An index mechanism which is performed by the user manually those indexes are can be called as non unique indexes. Whenever we apply an index mechanism on any particular column in the table then Oracle engine internally maintains a separate table called index table which maintains chain index relationship between the regular table and normal table.
Syntax to create an index
CREATE UNIQUE INDEX<Index name> AS TABLE NAME <Column name>
create unique index ix on ashok(no);
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