What Does Oracle rowid mean?

Official Website description

Owid: a globally unique address for a row in a database.

 

Rowid can be divided into extended rowid and restricted rowied.

 

1.1 restricted rowid

Internally, the rowid is a structure that holds information that the database server needs to access a row. The restricted internal rowid is 6 bytes on most platforms.

 

Each restricted rowid provided des the following data:

(1) datafile identifier

(2) block identifier

(3) Row identifier

 

The restricted rowid pseudo docolumn is returned to client applications in the form of an18-character string with a hexadecimal encoding of the datablock, row, and datafile components of the rowid.

 

1.2 extended rowid

The extended rowid datatype provided des the data in the restricted rowid plus a data object number. The data object number is an identification number assigned to every database segment.
Extended internal rowid is 10 bytes on most platforms.

Data in an extended rowid pseudo docolumn is returned to the client application in the form ofan 18-character string (for example, "aaaa8maalaaaaqkaaa"), which represents a Base 64 encoding of the Components
Of the extended rowid in a four-piece format, oooooofffbbbbbbrrr.
Extended rowids are not available directly. You canuse A supplied package, dbms_rowid, to interpret extended rowid contents. The package functions extract and provide information that wowould be available
Directly from a restricted rowid as well as information specific to extended rowids.

 

What Does Oracle rowid mean?
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Rowid is a pseudo column of the database. When a table is created, the database automatically creates a rowid column for each table.
Uniquely identifies a row of records.
Rowid is the actual physical address that stores each record, and the access to the record is based on rowid.
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The physical address of each record,
You can use rowid to search for record rows in a database.
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Uniquely identifies a row of records
Select rowid, * from Table Name
Give it a try and you will understand
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Rowid is like the home address on the envelope to be searched for when the postman delivers the mail. Each rowid does not repeat. It allows Oracle to search for data faster.
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Rowid is a pseudo column, corresponding to the block number, row number, row number ..
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Rowid

For each row in the database, the rowid pseudo column returns a row's
Address. rowid values contain information necessary to locate
Row:

* Which data block in the data file
* Which row in the data block (first row is 0)
* Which data file (first file is 1)

In most cases, a rowid value uniquely identifies a row in
Database. However, rows in different tables that are stored

Together in the same cluster can have the same rowid.

Values of the rowid pseudo docolumn have the datatype rowid.

Rowid values have several important uses:

* They are the fastest means of accessing a single row.
* They can show you how a table's rows are stored.
* They are unique identifiers for rows in a table.

A rowid does not change during the life time of its row. However,

You shoshould not use rowid as a table's primary key. If you delete
And reinsert a row with the import and export utilities,
Example, its rowid may change. If you delete a row, Oracle may
Reassign its rowid to a new row inserted later.

Although you can use the rowid pseudo column in the select and where
Clses of a query, these pseudo docolumn values are not actually
Stored in the database. You cannot insert, update, or delete

Value of the rowid pseudo column.

Example:

This statement selects the address of all rows that contain data
Employees in department 20:

Select rowid, ename
From EMP
Where deptno = 20

Rowid ename
---------------------------
0000000f. 0000.0002 Smith
0000000f. 0003.0002 Jones
0000000f. 0007.0002 Scott

0000000f. 000a. 0002 Adams
10000000f. 000c. 0002 Ford

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Pseudo Columns

A pseudo column behaves like a table column, but is not actually
Stored in the table. You can select from pseudo columns, but you
Cannot insert, update, or delete their values. This section
Describes these pseudo columns:

* Currval
* Nextval
* Level
* Rowid
* Rownum

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Pseudo column:
A pseudo column is like a column in a data table, but it is not actually stored in a table.
You can extract values from these pseudo Columns
However, you cannot insert, update, or delete values.
These pseudo columns are described as follows:

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The unique identifier of a record in the Oracle database.