A variable is a portion of memory that contains a value. A value can be any kind of information, e.g. names, numbers, text, sounds, images, etc.
A variable's value can change, depending on what is stored in the memory location by functions or by commands running within a program.
A variable declaration specifies the variable's name, data type, and value, and allocates the initial amount of storage for it.
The declaration can also assign an initial value to the variable and enforce the NOT NULL constraint.
Note that variables are initialized every time a block or subprogram is entered. By default, variables are initialized to NULL.
Whether public or private, variables declared within a package specification are initialized only once for each session.
An initialization clause is required when declaring NOT NULL variables. If you use %ROWTYPE to declare a variable, initialization is not allowed.
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