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You can define a column or variable with a ROWID datatype, but Oracle doesn??™t
guarantee that any value placed in this column or variable is a valid ROWID.
Datatypes | 87
ORA_ROWSCN
Oracle Database 10g and later releases support a pseudocolumn ORA_ROWSCN,
which holds the System Change Number (SCN) of the last transaction that modified
the row. You can use this pseudocolumn to check easily for changes in the
row since a transaction started. For more information on SCNs, see the discussion
of concurrency in Chapter 8.
LOB
A LOB, or large object datatype, can store up to 4 GB of information. LOBs
come in three varieties:
??? CLOB, which can store only character data
??? NCLOB, which stores National Language character set data
??? BLOB, which stores data as binary information
Youcan designate that a LOB should store its data within the Oracle database or
that it should point to an external file that contains the data.
LOBs can participate in transactions. Selecting a LOB datatype from Oracle will
return a pointer to the LOB.


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