PLSQL | COMPOSE Function

The string in PL/SQL is actually a sequence of characters with an optional size specification.
The characters could be numeric, letters, blank, special characters or a combination of all.
The Compose Function in PLSQL is used to return a Unicode string.

The unistring values that can be combined with other characters in the compose function are:

1. unistr(‘\0300’) – grave accent ( ` )
2. unistr(‘\0301’) – acute accent ( ´ )
3. unistr(‘\0302’) – circumflex ( ^ )
4. unistr(‘\0303’) – tilde ( ~ )
5. unistr(‘\0308’) – umlaut ( ¨ )

Syntax:

COMPOSE( string )

Parameters Used:

string – It is used to specify the input value whose Unicode string needs to be created.

Supported Versions of Oracle/PLSQL:

1. Oracle 12c
2. Oracle 11g
3. Oracle 10g
4. Oracle 9i

Example:

DECLARE 
   Test_Char char := 'a';
   Test_Char2 char := 'e';
   
BEGIN 
   dbms_output.put_line(COMPOSE(Test_Char || unistr('\0308' ))); 
   dbms_output.put_line(COMPOSE(Test_Char || unistr('\0301' )));
   dbms_output.put_line(COMPOSE(Test_Char || unistr('\0303' ))); 
   dbms_output.put_line(COMPOSE(Test_Char2 || unistr('\0302' ))); 
   
END;  

Output:

ä
á
ã
ê