What does rowid mean in oracle

ROWID is an identifier that uniquely identifies a row in the Oracle database and consists of file number, area number, block number and slot number. It is used to ensure data integrity, improve query performance, and plays a role in replication and recovery operations. You can obtain the ROWID through the SELECT ROWID statement and use it when updating, deleting, creating an index, or replicating recovery. Note that ROWID is unique within a table but may be the same in different tables and may change when the table structure changes.

ROWID in Oracle

What is ROWID?

ROWID (row identifier) ​​is a string of unique identifiers for each row in the Oracle database. It is used to identify the physical location of a row in a database table.

Composition of ROWID

ROWID consists of the following parts:

• File number: identifies the data file where the data block is located.
• Area code: Determine the location of the data block in the data file.
• Block number: identifies the block where the line is located.
• Slot number: Position the exact position of the line in the block.

Purpose of ROWID

ROWID is mainly used for the following purposes:

• Ensure data integrity:ROWID does not change due to reordering or deletion of rows in the table. This helps prevent data corruption caused by concurrent access and transaction exceptions.
• Improve query performance: By using ROWID, Oracle can quickly locate rows without scanning the entire table.
• Replication and recovery operations: ROWID is very important in replication and recovery operations because it allows multi-version control and consistency.

Get ROWID

You can use the following method to get the ROWID of the row:

SELECT ROWID FROM table_name WHERE ...;

Use ROWID

ROWID can be used in the following situations:

• To update or delete a specific row:

  UPDATE table_name SET ... WHERE ROWID = ...;
  DELETE FROM table_name WHERE ROWID = ...;

• Create index:

  CREATE INDEX ON table_name (ROWID);

• Copy and restore operations:
  ROWID is used to identify and locate rows during copy and restore operations.

Note

• ROWID is unique in the table, but may be the same in different tables.
• ROWID may change when the table structure changes, such as adding or removing columns.

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