ROWID

SELECT department_id, rowid FROM hr.departments;
DEPARTMENT_ID ROWID
————- ——————
10 AAABQMAAFAAAAA6AAA
20 AAABQMAAFAAAAA6AAB
30 AAABQMAAFAAAAA6AAC
40 AAABQMAAFAAAAA6AAD

In this example:
• AAABQM is the data object number
• AAF is the relative file number
• AAAAA6 is the block number
• AAA is the row number for the department with ID = 10

• every row in a non clustered table of Oracle database is assigned a unique ROWID
• corresponds to the physical address of the row
• every table contains a pseudo column called ROWID
• fastest way to access a row
• Import, Export operations affect the values of ROWID
• the ROWID of a deleted row may be reassigned by Oracle
• cannot be modified
• can be queried
• may not be supported in non-Oracle databases
• can be used to understand a table's organization
• use of locks while using ROWID is recommended
• ORACLE8 uses extended rowid format
• Object Ids can refer to various row objects
• ROWID changes especially with index organized or partitioned tables. Because ROWIDs represent the physical location of a record/row, the ROWID will chang every time the record is physically moved
• The ROWID is intended to be immutable (that is, unchangeable)
• The ROWID is a valid data type of a column and is available in both SQL and Pl/SQL. It stores the ROWID pseudo column value of a row in the database.
• It's important to note that ROWID values are not necessarily unique within a database. It is entirely possible for two rows of two different tables stored in the same cluster to have the same ROWID
• ROWID may change if the row is physically moved on disk, such as:

                    Doing an export or import of the table
                    Doing ALTER TABLE XXXX MOVE
                    Doing ALTER TABLE XXXX SHRINK SPACE
                    Doing FLASHBACK TABLE XXXX
                    When splitting a partition
                    When updating a value so that it moves to a new partition
                    When combining two partitions