PL/SQL Constants
You can declare PL/SQL constants along with the value and can not change them throughout the program block. The constants declaration functionality is available in almost all programming languages.
Constant Syntax:
Syntax for declaring a constant variable is:
Constant_name CONSTANT Datatype[Size] := Value;
Here,Constant_name is a predefined name of the constant (similar to a variable name).CONSTANT is a reserved keyword.Data type is a valid PL/SQL data type.Size is an optional specification of data type. It holds maximum capacity value for the particular variable.Value must be assigned to a constant when it is declared. You can not assign or change it later.Each constant declaration is terminated by a semicolon.
Constant Example
In this example, we will store the employee number which is NOT NULL (compulsory), employee Name and employee department which is constant,
Example
DECLARE
eno number(5) NOT NULL := 2
ename varchar2(15) := 'Branson Devs';
edept CONSTANT varchar2(15) := 'Web Developer';
BEGIN
dbms_output.put_line('Declared Value:');
dbms_output.put_line(' Employee number: ' || eno || ' Employee Name: ' || ename);
dbms_output.put_line('Constant Declared:');
dbms_output.put_line(' Employee Department: ' || edept);
END;
/
Backward slash ‘/’ is indicated to execute the above PL/SQL Block Program.
Example Result
Declared Value:
Employee number: 2 Employee Name: Branson Devs
Constant Declared:
Employee Department: Web Developer
PL/SQL procedure successfully operation.
Variable/Constant Declarations Example
In this example, we will store the pi which is constant real number, radius and area which are real number,
Example
DECLARE
pi CONSTANT REAL := 3.14159;
radius REAL := 3;
area REAL := (pi * radius**2);
BEGIN
dbms_output.put_line(' PI: ' || pi || ' Radius: ' || radius);
dbms_output.put_line(' Area: ' || area);
END;
/
Example Result
PI: 3.14159 Radius: 1
Area: 28.27431