PLSQL : || Operator

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 || Operator in PLSQL is used to concatenate 2 or more strings together.
The result of concatenating two character strings is another character string.
The result has datatype CHAR and is limited to 2000 characters if both character strings are of datatype CHAR whereas if either string is of datatype VARCHAR2, the result has datatype VARCHAR2 and is limited to 4000 characters.
The CONCAT character function can also be used as an alternative to the vertical bar operator in PLSQL for concatenation of strings.

Syntax:

string1 || string2 [ || string_n ]

Parameters Used:

1. string1 –
   It is used to specify the first string to concatenate.
2. string2 –
   It is used to specify the second string to concatenate.
3. string_n –
   It is used to specify the nth string to concatenate.

Return Type:
The || operator returns a string value.

Supported Versions of Oracle/PLSQL:

1. Oracle 12c
2. Oracle 11g
3. Oracle 10g
4. Oracle 9i
5. Oracle 8i

Example-1:

DECLARE 
   Test_String string(10) := 'Hello ';
   Test_String2 string(10) := 'world!';
   
BEGIN 
   dbms_output.put_line((Test_String || Test_String2)); 
   
END; 

Output:

Hello world! 

Example-2:

DECLARE 
   Test_String string(10) := 'Geeks';
   Test_String2 string(10) := 'For';
   Test_String3 string(10) := 'Geeks';
   
BEGIN 
   dbms_output.put_line(Test_String || Test_String2 || Test_String3);   
END; 

Output:

GeeksForGeeks