Oracle PL/SQL Language Pocket Reference, 4th Edition

Variables and Program Data

PL/SQL programs normally are used to manipulate database information. You commonly do this by declaring variables and data structures in your programs, and then working with that PL/SQL-specific data.

A variable is a named instantiation of a data structure declared in a PL/SQL block (either locally or in a package). Unless you declare a variable as a CONSTANT, its value can be changed at any time in your program.

The following table summarizes the different types of program data.

Type	Description
Scalar	Variables made up of a single value, such as a number, date, or Boolean.
Composite	Variables made up of multiple values, such as a record, collection, or instance of a user-defined object type. See the sections "Records in PL/SQL,” "Collections in PL/SQL,” and "Object-Oriented Features.”
Reference	Logical pointers to values or cursors.
LOB	Variables containing large object (LOB) locators.

Scalar Datatypes

Scalar datatypes divide into four families: number, character, datetime, and Boolean. Subtypes further define a base datatype by restricting the values or size of the base datatype.

Numeric datatypes

Numeric datatypes represent real numbers, integers, and floating-point numbers. They are stored as NUMBER, PLS_INTEGER, and IEEE floating-point storage types.

Decimal numeric datatypes store fixed and floating-point numbers of just about any size. They include the subtypes NUMBER, DEC, DECIMAL, NUMERIC, FLOAT, REAL, and DOUBLE PRECISION. The maximum precision of a variable ...