Literals

A literal is an explicit numeric, string, character, or Boolean value not represented by an identifier. Numeric literal 147 and the Boolean literal FALSE are some of the examples.

Numeric Literals

The 2 kinds of numeric literals can be used in an arithmetic expression: integers & reals. The  integer literal is an optionally signed whole number without a decimal point. Some of the examples are shown below:

030, 6, -14, 0, +32767

A real literal is an optionally signed whole or fractional number with a decimal point. Some of the examples are shown below:

6.6667, 0.0, -12.0, 3.14,159, +8300.0, 0 .5 25

The PL/SQL considers numbers like 12.0 and 25. to be real even if they have integral values.

The Numeric literals cannot contain dollar signs or commas, however can be written using the scientific notation. Just suffix the number with an E (or e) followed by an optionally signed integer. A few examples are shown below:

2E5 1.0E-7 3.14159e0 -1E38 -9.5e-3

The E stands for "times ten to the power of." As the next illustration represents, the number after E is the power of ten by which the number before E must be multiplied (the double asterisk (**) is the exponentiation operator):

5E3 = 5 10**3 = 5 1000 = 5000

The number after E also correspond to the number of places the decimal point shift. In the last illustration, the implicit decimal point shifted three places to the right. In this illustration, it shifts three places to the left:

5E-3 = 5 10**-3 = 5 0.001 = 0.005

As the example below shows, if the value of a numeric literal falls outside the range 1E-130... 10E125, you obtain a compilation error:

DECLARE

n NUMBER;

BEGIN

n := 10E127; -- causes a 'numeric overflow or underflow' error

Character Literals

A character literal is an individual character enclosed by single quotes (apostrophes). The Character literals include all the printable characters in the PL/SQL character set: numerals, letters, spaces, and special symbols. Some examples are as shown:

'Z' '%' '7' ' ' 'z' '('

The PL/SQL is case sensitive within the character literals. For example, PL/SQL considers

the literals 'Z' and 'z' to be different. Also the character literals '0'..'9' are not equivalent to the integer literals but can be used in the arithmetic expressions as they are implicitly convertible to integers.

String Literals

A character value can be represented by an identifier or explicitly written as a string literal that is a sequence of zero or more characters enclosed by single quotes. Several examples are shown below:

'Hello, world!'

'XYZ Corporation'

'10-NOV-91'

'He said "Life is like licking honey from a thorn."'

'$1,000,000'

All the string literals except the null string ('') have datatype CHAR. Given that the apostrophes (single quotes) delimit string literals, how do you show an apostrophe within a string? As the next illustration shows, you write two single quotes that are not similar as writing a double quote:

"'Don't leave without saving the work."

The PL/SQL is case sensitive within string literals. For illustration, PL/SQL considers the following literals to be different:

'baker'

'Baker'

Boolean Literals

The Boolean literals are the predefined values TRUE, FALSE, & NULL (which stand for an unknown, missing, or inapplicable value). Keep in mind; the Boolean literals are values, and not the strings. For illustration, TRUE is no less a value than the number 25.