Oracle PL/SQL Language Pocket Reference, Second Edition

Variables and Program Data

PL/SQL programs are normally 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 or a collection
Reference	Pointers to values
LOB	Variables containing large object (LOB) locators

Scalar Datatypes

Scalar datatypes divide into four families: number, character, datetime, and Boolean.

Numeric datatypes

Numeric datatypes are further divided into decimal, binary integer, and PLS_INTEGER storage types.

Decimal numeric datatypes store fixed and floating-point numbers of just about any size. They include NUMBER, DEC, DECIMAL, NUMERIC, FLOAT, REAL, and DOUBLE PRECISION. The maximum precision of a variable with type NUMBER is 38 digits, which yields a range of values from 1.0E-129 through 9.999E125. (This range of numbers would include the mass of an electron over the mass of the universe or the size of the universe in angstroms.)

Variables of type NUMBER can be declared with precision and scale, ...