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ROWID OF A RECORD (PSUEDO COLUMN)

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Written by Manish Sen
Wednesday, 10 September 2008

Rowid Is a Psuedo Column in oracle tables :

For each row in the database the row id psuedocolomn returns a row address .oracle 8 rowid value contain information nessasary to locate a row.

1. which data object number of the object.

2. which data bloch in the datafile.

3. which row in the data block ( first row is 0).

4. which datafile (first file is one) the file no is releted to table spaces.

usully a row id value uniquly identifies a row in the database , however row in the different table that r stored together in the same cluster can have the same rowid .

row id have saveral important uses :

1.they are the fastest way to access a single row.

2. they can show you how a table 's row are stored.

3they r unique identifiers for row in a table.

you should not use row id as table's primary key. If you delete and reinsert a row with the import/export utilities, its rowid may chang. if you delete a row, oracle may assign its rowid to a new row inserted later . although you can use the rowid psuedocolomn in the select and where clause of a query.