Constants and literals in plsq

PL/SQL Constants:

A constant holds a value used in a PL/SQL block that does not change throughout the program. It is a user-defined literal value.

Syntax to declare a constant:

constant_name CONSTANT datatype := VALUE;

Where:

constant_name – is a valid identifier name.
CONSTANT – is a keyword.
VALUE – is a value which must be assigned to a constant when it is declared. You cannot assign a value later.

Example:

DECLARE
   -- constant declaration
   pi constant number := 3.141592654;
   -- other declarations
   radius number(5,2); 
   dia number(5,2); 
   circumference number(7, 2);
   area number (10, 2);
BEGIN 
   -- processing
   radius := 10.5; 
   dia := radius * 2; 
   circumference := 2.0 * pi * radius;
   area := pi * radius * radius;
   -- output
   dbms_output.put_line('Radius: ' || radius);
   dbms_output.put_line('Diameter: ' || dia);
   dbms_output.put_line('Circumference: ' || circumference);
   dbms_output.put_line('Area: ' || area);
END;
/

Output:

Radius: 10.5
Diameter: 21
Circumference: 65.97
Area: 346.36

PL/SQL Literals:

Literals is an explicit numeric, character, string or Boolean values which are not represented by identifiers i.e. TRUE, NULL, w3schools etc.
Note: PL/SQL literals are case-sensitive.

Types of literals in PL/SQL:

1. Numeric Literals (765, 23.56 etc.).
2. Character Literals (‘A’ ‘ 3. String Literals (tutorialspointexamples.com etc.).
4. BOOLEAN Literals (TRUE, FALSE and NULL).
5. Date and Time Literals (‘2016-12-25’ ‘2016-02-03 12:10:01’ etc.).