A delimiter is a character, or character combination, that has a special meaning in PL/SQL.

Do not embed any others characters (including whitespace characters) inside a delimiter.

Table 3-2 summarizes the PL/SQL delimiters.

Identifiers name PL/SQL elements, which include:

• Constants

• Cursors

• Exceptions

• Keywords

• Labels

• Packages

• Reserved words

• Subprograms

• Types

• Variables

Every character in an identifier, alphabetic or not, is significant. For example, the identifiers lastname and last_name are different.

You must separate adjacent identifiers by one or more whitespace characters or a punctuation character.

Except as explained in "Quoted User-Defined Identifiers", PL/SQL is case-insensitive for identifiers. For example, the identifiers lastname, LastName, and LASTNAME are the same.

A literal is a value that is neither represented by an identifier nor calculated from other values.

For example, 123 is an integer literal and 'abc' is a character literal, but 1+2 is not a literal.

PL/SQL literals include all SQL literals (described in Oracle Database SQL Language Reference), including BOOLEAN literals. A BOOLEAN literal is the predefined logical value TRUE, FALSE, or NULL. NULL represents an unknown value.

When using character literals in PL/SQL, remember:

• Character literals are case-sensitive.

  For example, 'Z' and 'z' are different.

• Whitespace characters are significant.

  For example, these literals are different:

  'abc'
  ' abc'
  'abc '
  ' abc '
  'a b c'
  

• PL/SQL has no line-continuation character that means "this string continues on the next source line." If you continue a string on the next source line, then the string includes a line-break character.

  For example, this PL/SQL code:

  BEGIN
    DBMS_OUTPUT.PUT_LINE('This string breaks
  here.');
  END;
  /
  

  Prints this:

  This string breaks
  here.
  

  If your string does not fit on a source line and you do not want it to include a line-break character, then construct the string with the concatenation operator (||).

  For example, this PL/SQL code:

  BEGIN
    DBMS_OUTPUT.PUT_LINE('This string ' ||
                         'contains no line-break character.');
  END;
  /
  

  Prints this:

  This string contains no line-break character.
  

  For more information about the concatenation operator, see "Concatenation Operator".

• '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.

  However, this NULL value is not the BOOLEAN value NULL.

• An ordinary character literal is composed of characters in the database character set.

  For information about the database character set, see Oracle Database Globalization Support Guide.

• A national character literal is composed of characters in the national character set.

  For information about the national character set, see Oracle Database Globalization Support Guide.

• You can use Q or q as part of the character literal syntax to indicate that an alternative quoting mechanism will be used. This mechanism allows a wide range of delimiters for a string as opposed to simply single quotation marks.

  For more information about the alternative quoting mechanism, see Oracle Database SQL Language Reference.

  Live SQL:

  You can view and run examples of the Q mechanism at Alternative Quoting Mechanism (''Q'') for String Literals

A pragma is an instruction to the compiler that it processes at compile time.

A pragma begins with the reserved word PRAGMA followed by the name of the pragma. Some pragmas have arguments. A pragma may appear before a declaration or a statement. Additional restrictions may apply for specific pragmas. The extent of a pragma’s effect depends on the pragma. A pragma whose name or argument is not recognized by the compiler has no effect.

pragma ::=

Description of the illustration pragma.eps

For information about pragmas syntax and semantics, see :

• "AUTONOMOUS_TRANSACTION Pragma"

• "COVERAGE Pragma"

• "DEPRECATE Pragma"

• "EXCEPTION_INIT Pragma"

• "INLINE Pragma"

• "RESTRICT_REFERENCES Pragma"

• "SERIALLY_REUSABLE Pragma"

• "SUPPRESSES_WARNING_6009 Pragma"

• "UDF Pragma"

The PL/SQL compiler ignores comments. Their purpose is to help other application developers understand your source text.

Typically, you use comments to describe the purpose and use of each code segment. You can also disable obsolete or unfinished pieces of code by turning them into comments.

You can put whitespace characters between lexical units, which often makes your source text easier to read.

DECLARE
  x    NUMBER := 10;
  y    NUMBER := 5;
  max  NUMBER;
BEGIN
  IF x>y THEN max:=x;ELSE max:=y;END IF;  -- correct but hard to read
  
  -- Easier to read:
  
  IF x > y THEN
    max:=x;
  ELSE
    max:=y;
  END IF;
END;
/