Which Oracle access method is the fastest way for Oracle to retrieve a single row?
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Primary key access
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Access via unique index
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Table access by ROWID
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Full table scan
Access by ROWID is fastest because ROWID is the physical address of the row in the data file. Oracle can go directly to that location without traversing index structures or scanning. Primary key and unique index access require index traversal first.
Accessing a row directly by its ROWID is the fastest retrieval method in Oracle because the ROWID encodes the exact physical location (file, block, and row number) of the row, letting Oracle go straight to it with no index lookup or search at all. Primary key and unique index access are fast too, but they still require traversing an index structure first to find the ROWID before fetching the row — an extra step that direct ROWID access skips.