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No it's not possible to have more than one primary index on same relation. In primary index the search key is the primary key/Alternate key and it is physically ordered in DB, so other keys will automatically be  unordered hence at most 1 primary index is possible for a relation.
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If two or more attributes are ordered then yes. Example: Roll Number(unique within institute) and enrollment number(unique within Mumbai University) of relation for an institute.
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Primary indexing is always done on ordered key field,i.e you can order the database file only on one field,right ? That’s why,it is not possible to have 2 primary indexing

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