Hello Friends ,

Lots of My dear friends and viewers have requested to know about ROWID and its Its details .

This Post I try to give more details about Rowid and How best can we use it to locate the unique Record

Rowid is also called as Pseudo Column .


For each row in the database, the ROWID pseudo ccolumn returns the address of the row. Oracle Database rowid values contain information necessary to locate a row:

•     The data object number of the object

•     The data block in the datafile in which the row resides

•     The position of the row in the data block (first row is 0)

•     The datafile in which the row resides (first file is 1). The file number is relative to the tablespace.

Usually, a rowid value uniquely identifies a row in the database. However, rows in different tables that are stored together in the same cluster can have the same rowid.

Values of the ROWID pseudocolumn have the datatype ROWID or UROWID. Please refer to "ROWID Datatype" and "UROWID Datatype" for more information.

Rowid values have several important uses:

•     They are the fastest way to access a single row.

•     They can show you how the rows in a table are stored.

•     They are unique identifiers for rows in a table.

You should not use ROWID as the primary key of a table. If you delete and reinsert a row with the Import and Export utilities, for example, then its rowid may change. If you delete a row, then Oracle may reassign its rowid to a new row inserted later.

Although you can use the ROWID pseudo column in the SELECT and WHERE clause of a query, these pseudo column values are not actually stored in the database. You cannot insert, update, or delete a value of the ROWID pseudo column.

Example This statement selects the address of all rows that contain data for employees in department 20:

SELECT ROWID, last_name 

   FROM XXGHAN

   WHERE department_id = 50;


With Help of ROWID , We can delete the duplicate records as well as an example

DELETE FROM XXGH WHERE ROWID NOT IN (SELECT MAX(ROWID) FROM XXGH GROUP BY EMPNO);



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