14.14 Constant Declaration

A constant holds a value that does not change. A constant declaration specifies the name, data type, and value of the constant and allocates storage for it. The declaration can also impose the NOT NULL constraint.

Topics

• Syntax

• Semantics

• Examples

• Related Topics

Syntax

constant_declaration ::=

Description of the illustration constant_declaration.eps

(datatype ::=, expression ::=)

Semantics

constant_declaration

constant

Name of the constant that you are declaring.

datatype

Data type for which a variable can be declared with an initial value.

NOT NULL

Imposes the NOT NULL constraint on the constant.

For information about this constraint, see "NOT NULL Constraint".

expression

Initial value for the constant. expression must have a data type that is compatible with datatype. When constant_declaration is elaborated, the value of expression is assigned to constant.

Examples

• Example 3-12, "Constant Declarations"

• Example 3-13, "Variable and Constant Declarations with Initial Values"

Related Topics

In this chapter:

• "Collection Variable Declaration"

• "Record Variable Declaration"

• "%ROWTYPE Attribute"

• "Scalar Variable Declaration"

• "%TYPE Attribute"

In other chapters:

• "Declaring Constants"

• "Declaring Associative Array Constants"

• "Declaring Record Constants"