Varying-Width Character Data

• You can create the following tables:
  • With CLOB/NCLOB columns even if you use a varying-width CHAR/NCHAR database character set

  • With a type that has a CLOB attribute irrespective of whether you use a varying-width CHAR database character set

• You cannot create the following tables:
  • With NCLOBs as attributes of object types

CLOB, NCLOB Values are Stored Using 2 Byte Unicode for Varying-Width Character Sets

CLOB/NCLOB values are stored in the database using the fixed width 2 byte Unicode character set if the database CHAR/NCHAR character set is varying-width.

• Inserting Data. When you insert data into CLOBs, the data input can be in a varying-width character set. This varying-width character data is implicitly converted into Unicode before data is stored in the database.

• Reading the LOB. Conversely, when reading the LOB value, the stored Unicode value is translated to the (possibly varying-width) character set that you request on either the client or server.

Note that all translations to and from Unicode are implicitly performed by Oracle.

NCLOBs store fixed-width data.

You can perform all LOB operations on CLOBs (read, write, trim, erase, compare, e.t.c.) All programmatic environments that provide access to CLOBs work on CLOBs in databases where the CHAR/NCHAR character set is of varying-width. This includes SQL, PL/SQL, OCI, PRO*C, DBMS_LOB, and so on.

For varying-width CLOB data you need to also consider whether the parameters are specified in characters or bytes.

See Also:

Chapter 3, "LOB Programmatic Environments":

• "Offset and Amount Parameters: Fixed-Width Versus Varying-Width, Character or Byte For DBMS_LOB Package"

• "Offset and Amount Parameters: Fixed-Width Versus Varying-Width, Character or Byte With OCI"