A literal is an explicit numeric, character, string, or Boolean value not represented by an identifier.
Numeric Literals
Two kinds of numeric literals can be used in arithmetic expressions:
1 Integers
2.Reals.
An integer literal is an whole number without a decimal point.it may or may not have a sign Some examples follow:
03 60 -236 0 +32767
A real literal is an whole or fractional number with a decimal point(may or may not be signed). Several examples follow:
6.6667 0.0 -12.0 3.14159 +8300.00 .5 25.
PL/SQL considers numbers such as 12.0 and 25. to be reals even though they have integral values.
Numeric literals cannot contain dollar signs or commas, but can be written using scientific notation. Simply suffix the number with an E (or e) followed by an optionally signed integer. A few examples follow:
2E5 1.0E-7 3.14159e0 -1E38 -9.5e-3
E stands for "times ten to the power of." As the next example shows, 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 corresponds to the number of places the decimal point shifts. In the last example, the implicit decimal point shifted three places to the right. In this example, it shifts three places to the left:
5E-3 = 5 * 10**-3 = 5 * 0.001 = 0.005
As the following example shows, if the value of a numeric literal falls outside the range 1E-130 .. 10E125, you get 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). Character literals include all the printable characters in the PL/SQL character set: letters, numerals, spaces, and special symbols. Some examples follow:
'Z' '%' '7' ' ' 'z' '('
PL/SQL is case sensitive within 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 integer literals but can be used in arithmetic expressions because they are implicitly convertible to integers.
String Literals
A character value can be represented by an identifier or explicitly written as a string literal, which is a sequence of zero or more characters enclosed by single quotes. Several examples follow:
'Hello, world!'
'XYZ Corporation'
'10-NOV-91'
'He said "Life is like licking honey from a thorn."'
'$1,000,000'
All string literals except the null string ('') have datatype CHAR.
Given that apostrophes (single quotes) delimit string literals, how do you represent an apostrophe within a string? As the next example shows, you write two single quotes, which is not the same as writing a double quote:
'Don''t leave without saving your work.'
PL/SQL is case sensitive within string literals. For example, PL/SQL considers the following literals to be different:
'baker'
'Baker'
Boolean Literals
Boolean literals are the predefined values TRUE, FALSE, and NULL (which stands for a missing, unknown, or inapplicable value). Remember, Boolean literals are values, not strings. For example, TRUE is no less a value than the number 25.
Datetime Literals
Datetime literals have various formats depending on the datatype. For example:
DECLARE
d1 DATE := DATE '1998-12-25';
t1 TIMESTAMP := TIMESTAMP '1997-10-22 13:01:01';
t2 TIMESTAMP WITH TIME ZONE := TIMESTAMP '1997-01-31 09:26:56.66
+02:00';
-- Three years and two months
-- (For greater precision, we would use the day-to-second interval)
i1 INTERVAL YEAR TO MONTH := INTERVAL '3-2' YEAR TO MONTH;
-- Five days, four hours, three minutes, two and 1/100 seconds
i2 INTERVAL DAY TO SECOND := INTERVAL '5 04:03:02.01' DAY TO SECOND;
...
You can also specify whether a given interval value is YEAR TO MONTH or DAY TO SECOND. For example, current_timestamp - current_timestamp produces a value of type INTERVAL DAY TO SECOND by default. You can specify the type of the interval using the formats:
• (interval_expression) DAY TO SECOND
• (interval_expression) YEAR TO MONTH
