A literal is a constant value.
For example, 123 is an integer literal and 'abc' is a character literal, but 2+2 is not a literal.
PL/SQL literals include all SQL literals and BOOLEAN literals.
A BOOLEAN literal is the predefined logical value TRUE, FALSE, or NULL.
NULL represents an unknown value.
Character literals are case-sensitive. For example, 'A' and 'a' are different.
Whitespace characters in Character literals are significant. For example, 'abc', ' abc', 'abc ', ' abc ', 'a b c' are different.
If you continue a string on the next source line, then the string includes a line-break character. For example, this PL/SQL code:
SQL> SQL> BEGIN-- from ww w . ja va 2 s. c om 2 DBMS_OUTPUT.PUT_LINE('this is a test 3 here.'); 4 END; 5 / this is a test here. PL/SQL procedure successfully completed. SQL>
To append two line single line character literals, use concatenation operator ( ||).
SQL> SQL> BEGIN-- w w w .j a v a2s . c om 2 DBMS_OUTPUT.PUT_LINE('This string ' || 3 'this is a test.'); 4 END; 5 / This string this is a test. PL/SQL procedure successfully completed. SQL>
'0' through '9' are not equivalent to the integer literals 0 through 9.
However, because PL/SQL converts them to integers, you can use them in arithmetic expressions.
A character literal with zero characters has the value NULL and is called a null string.