PLSQL Constants

In this post we will discuss about PLSQL Constants in Oracle, How do you declare a constant variable in PL SQL, how to Declare a constant in Oracle stored procedure

Oracle PLSQL Constant

• Oracle PLSQL constant is just like any other procedural language and Its value does not change during the execution of the program
• Constants must be declared for use in procedural and SQL code, although the datatypes available in SQL are only a subset of those available in PL/SQL.

How do you declare a constant variable in PL SQL

• All constants must be declared before they are referenced.
• Declaration involves the name of the constant followed by its data type.
• Remember that each constant must be declared on a separate line and multiple constants cannot be defined in the same statement.
• All statements must end with a semicolon
• The declarations of constant definitions must contain the CONSTANT keyword and must be assigned a value as part of the definition. Subsequent attempts to assign a value to a constant will result in an error

General Syntax

variable_name CONSTANT datatype [NOT NULL := value ];

(1) variable_name is the name of the variable.

(2) datatype is a valid PL/SQL datatype.

Example of declaring Constants:

v_global constant number := 200; 
V_DEPT  CONSTANT NUMBER (6) DEFAULT 160;

• Constants cannot be changed.
• You must initialize constants at the time of declaration.

Example as full Plsql Block

DECLARE
c_limit CONSTANT REAL := 1000.00; -- SQL data type
max_days_in_year CONSTANT INTEGER := 266; -- SQL data type
u_legend CONSTANT BOOLEAN := TRUE; -- PL/SQL-only data type
BEGIN
NULL;
END;
/

Let’s try to assign some value to the constant variable

DECLARE
c_limit CONSTANT REAL := 1000.00; -- SQL data type
max_days_in_year CONSTANT INTEGER := 266; -- SQL data type
u_legend CONSTANT BOOLEAN := TRUE; -- PL/SQL-only data type
BEGIN
c_limit :=1;
END;
/
PLS-00363: expression 'c_limit' cannot be used as an assignment target

So it has received an error if we assign any value to the constant in the begin block

PLSQL Constants are an important construct and are quite used in PLSQL Programming. I hope you this post on PLSQL Constants in Oracle, How do you declare a constant variable in PL SQL, how to Declare a constant in Oracle stored procedure

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