PL/SQL Constants: Simplifying Code Stability
In PL/SQL, a constant is a fixed value that remains unchanged throughout a
program, offering a streamlined way to manage and update specific values.
Constants are particularly useful when you want to use a consistent value
across multiple parts of your code.
Syntax for Declaring a Constant:
constant_name CONSTANT datatype := VALUE;
- constant_name: The name assigned to the constant.
- datatype: The data type of the constant.
- VALUE: The fixed value assigned to the constant when declared, and it cannot be changed later.
Example:
The simple program that uses a constant to convert temperatures from
Celsius to Fahrenheit:
DECLARE
-- Declare the constant for Celsius to Fahrenheit
conversion
CELSIUS_CONSTANT CONSTANT NUMBER := 9.0 / 5.0;
-- Other variable declarations
celsius_temperature NUMBER(5,2) := 25.0;
fahrenheit_temperature NUMBER(5,2);
BEGIN
-- Processing: Convert Celsius to Fahrenheit
fahrenheit_temperature := (celsius_temperature *
CELSIUS_CONSTANT) + 32.0;
-- Output
dbms_output.put_line('Celsius Temperature: ' ||
celsius_temperature);
dbms_output.put_line('Fahrenheit Temperature: ' ||
fahrenheit_temperature);
END;
Output:
Celsius Temperature: 25.0
Fahrenheit Temperature: 77.0
PL/SQL procedure successfully completed.
PL/SQL Literals:
In PL/SQL, literals are specific values that are not represented by
identifiers. They come in various types, including numeric, character,
string, boolean, and date/time literals. These literals are
case-sensitive, meaning 'Hello' and 'hello' would be considered
different.
Types of PL/SQL Literals:
1.Numeric Literals:
Examples: 123, 4567, 78.9
2.Character Literals:
Examples: 'X', '@', '5', ' ', 'm', '!'
3.String Literals:
Example: 'Greetings, World!'
4.BOOLEAN Literals:
Examples: TRUE, FALSE, NULL
5.Date and Time Literals:
Examples: '15-03-2005', '2023-08-10 18:30:00'
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