Oracle PL/SQL constants/variables/scalar (to be improved)

A constant
The definition of a constant must include the keyword constant.
Example: zero_value constant number: = 0;

2 variables
2.1) Declare Variables
Variable_name [constant] databyte [not null] [: = | default expression];
Example: V1 varchar2 (25 );

2.2) assign values to variables
Two methods are available.
1. assign values to variables directly
Example: V1: = 'jack ';
2. assign values to variables through SQL select into or fetch
For example:
Select name into V1 from customer where id = 10;

Scalar)
I. Digital

Datatype	Range	Subtypes	Description
Binary_integer	-214748 to 2147483647	Natural Natural Npositive Positiven Signtype	Used to store single-byte integers. The storage length must be less than the number value. Subtype used to limit the range ): Natural: used for non-negative numbers, and null Positive: used for positive numbers and null Natura1n: used only for non-negative values, not for null values Positiven: used only for positive numbers, not for null values Signtype: only values:-1, 0, or 1.
Number

Ii. Balanced type

Datatype	Range	Subtypes	Description
Char	Maximum length: 32767 bytes	Character	Stores fixed-length strings. If the length is not determined, the default value is 1.
Long	Maximum length: 2147483647 bytes		Store variable-length strings
Raw	Maximum length: 32767 bytes
Longraw	Maximum length: 2147483647 bytes
Rowid	18 bytes
Varchar2	Maximum length: 32767 bytes

Iii. Date and Boolean

References
Http://www.qqread.com/oracle/b412122105_2.html