ROWID

A ROWID (Oracle) — or the equivalent physical row identifier in other databases, such as PostgreSQL's ctid — is a pseudo-column pointing to a row's exact physical storage location. Looking up a row by ROWID is the fastest possible access path, since it skips index traversal entirely.

In Oracle, a ROWID encodes the data object, data block, and row-within-block location, and is what every B-tree index entry actually points to internally. It generally stays stable unless the row physically moves — for example during certain kinds of updates or table reorganisation.

PostgreSQL's ctid plays a similar role but is explicitly documented as unstable across a VACUUM FULL, which physically rewrites the table — so neither identifier should be stored long-term as if it were a permanent key; that's what a primary key is for.

Example

-- Oracle: fetch a row directly by its physical address
SELECT ROWID, last_name FROM employees WHERE employee_id = 100;