UNIQUE Index & NON UNIQUE Index

UNIQUE INDEX

Unique indexes guarantee that no two rows of a table have duplicate values in the columns that define the index.

Unique index is automatically created when primary key or unique constraint is created.

Ex: SQL> create unique index stud_ind on student(sno);

NON-UNIQUE INDEX

Non-Unique indexes do not impose the above restriction on the column values.

Ex: SQL> create index stud_ind on student(sno);