Syntax

Purpose

DECOMPOSE takes as its first argument a character value string and returns the result of applying one of the Unicode decompositions to it. The decomposition to apply is determined by the second, optional parameter. If the character set of the first argument is not one of the Unicode character sets, DECOMPOSE returns the argument unmodified.

If the second argument to DECOMPOSE is the string CANONICAL (case-insensitively), DECOMPOSE applies canonical decomposition, as described in the Unicode Standard definition D68, and returns a string in the NFD normalization form. If the second argument is the string COMPATIBILITY, DECOMPOSE applies compatibility decomposition, as described in the Unicode Standard definition D65, and returns a string in the NFKD normalization form. The default behavior is to apply the canonical decomposition.

In a pessimistic case, the return value of DECOMPOSE may be a few times longer than string. If a string to be returned is longer than the maximum length VARCHAR2 value in a given runtime environment, the value is silently truncated to the maximum VARCHAR2 length.

Both arguments to DECOMPOSE can be of any of the data types CHAR, VARCHAR2, NCHAR, or NVARCHAR2. Other data types are allowed if they can be implicitly converted to VARCHAR2or NVARCHAR2. The return value of DECOMPOSE is in the same character set as its first argument.

CLOB and NCLOB values are supported through implicit conversion. If string is a character LOB value, then it is converted to a VARCHAR2 value before the DECOMPOSE operation. The operation will fail if the size of the LOB value exceeds the supported length of the VARCHAR2 in the particular execution environment.

Examples

The following example decomposes the string "Châteaux" into its component code points:

SELECT DECOMPOSE ('Châteaux')
  FROM DUAL; 

DECOMPOSE
---------
Châteaux