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The Structure Of A Function

The structure of a stored function consists of the following five sections:

  Function declaration—Function name, parameters, and return datatype.
  Variable declarations—Variables, constants, and user-defined exceptions.
  Executable declarations —Local procedures and functions.
  Body—The internal logic of the function.
  Exception handling—Handlers for exceptions likely to occur while the function is executing.

Each section of a function has specific components, which are discussed in the following sections.

The Function Declaration

The function declaration consists of three distinct portions: function name, parameter definitions, and return datatypes.

  Function name—The name of the function, which identifies the function to other stored objects.
  Parameter definitions—The names, parameter types, datatypes, and default values of the function’s parameters, which specify how the function must be called.
  Return datatype—The datatype that the function returns, which specifies what type of input the calling code should expect as a result.

The function declaration is highlighted in Listing 5.15.

Listing 5.15 The function declaration.

FUNCTION Parse_String (vStringToParse IN    varchar2)

  RETURN Global_Types.VARCHAR2_TABTYPE

IS

  iStringPos              integer;
  biIndex                 binary_integer := 0;
  DELIMITER      CONSTANT char (1) := '^';
  vString                 varchar2 (2000);
  Return_tab              VARCHAR2_TABTYPE;

  FUNCTION DelimiterPosition (vString IN     varchar2)
    RETURN integer;

  FUNCTION NextWord (vCheckString IN     varchar2)

    RETURN varchar2

  IS

  BEGIN
    iStringPos := DelimiterPosition (vString => vCheckString));
    IF (iStringPos > 0) THEN
       RETURN (substr (vCheckString, 1, iStringPos);
    END IF;

    RETURN NULL;
  END NextWord;

  FUNCTION DelimiterPosition (vString IN     varchar2)

    RETURN integer

  IS

  BEGIN
    RETURN (instr (vString, DELIMITER));
  END DelimiterPosition;

BEGIN
  vString := vStringToParse;

  LOOP
    Return_tab (biIndex) := NextWord;
     --
     -- If there are no more elements in the string, return
     -- the table.
     --
     IF (iStringPos = 0) THEN
         RETURN Return_tab;
     END IF;

     Return_tab (biIndex) := substr (vString, 1, (iStringPos - 1));

     biIndex := biIndex + 1;

     --
     -- Chop off the first portion of the string.
     --
     vString := substr (vString, (iStringPos + 1));
   END LOOP;

EXCEPTION
  WHEN VALUE_ERROR THEN
      Log_System_Error (vErrorLocation => 'Parse_String',
                        vErrorText     => SQLERRM);
END;

Variable Declarations

The declarations section of a function allows you to define local variables, constants, and user-defined exceptions used by the function. These definitions are highlighted in Listing 5.16.

Listing 5.16 The variable declaration section of a function.

FUNCTION Parse_String (vStringToParse IN    varchar2)

  RETURN Global_Types.VARCHAR2_TABTYPE

IS

  iStringPos              integer;
  biIndex                 binary_integer := 0;
  DELIMITER      CONSTANT char (1) := '^';
  vString                 varchar2 (2000);
  Return_tab              VARCHAR2_TABTYPE;

  FUNCTION DelimiterPosition (vString IN     varchar2)
     RETURN integer;

  FUNCTION NextWord (vCheckString IN     varchar2)

     RETURN varchar2

  IS

  BEGIN
    iStringPos := DelimiterPosition (vString => vCheckString));
    IF (iStringPos > 0) THEN
       RETURN (substr (vCheckString, 1, iStringPos));
    END IF;

    RETURN NULL;
  END NextWord;

  FUNCTION DelimiterPosition (vString IN     varchar2)

    RETURN integer

  IS

  BEGIN
    RETURN (instr (vString, DELIMITER));
  END DelimiterPosition;

BEGIN
  vString := vStringToParse;

 LOOP
   Return_tab (biIndex) := NextWord;
    --
    -- If there are no more elements in the string, return
    -- the table.
    --
    IF (iStringPos = 0) THEN
       RETURN Return_tab;
    END IF;

    Return_tab (biIndex) := substr (vString, 1, (iStringPos - 1));

    biIndex := biIndex + 1;

    --
    -- Chop off the first portion of the string.
    --
    vString := substr (vString, (iStringPos + 1));
  END LOOP;

EXCEPTION
  WHEN VALUE_ERROR THEN
      Log_System_Error (vErrorLocation => 'Parse_String',
                        vErrorText     => SQLERRM);
END;

Executable Declarations

The declarations of local procedures and functions are made in the executable declarations section of a function. These definitions are highlighted in Listing 5.17.

Listing 5.17 The executable declarations of a function.

FUNCTION Parse_String (vStringToParse IN    varchar2)

  RETURN Global_Types.VARCHAR2_TABTYPE

IS
  iStringPos              integer;
  biIndex                 binary_integer := 0;
  DELIMITER      CONSTANT char (1) := '^';
  vString                 varchar2 (2000);
  Return_tab              VARCHAR2_TABTYPE;

  FUNCTION DelimiterPosition (vString IN     varchar2)
     RETURN integer;

  FUNCTION NextWord (vCheckString IN     varchar2)

     RETURN varchar2

  IS

  BEGIN
    iStringPos := DelimiterPosition (vString => vCheckString);
    IF (iStringPos > 0) THEN
       RETURN (substr (vCheckString, 1, iStringPos));
    END IF;

    RETURN NULL;
  END NextWord;

  FUNCTION DelimiterPosition (vString IN     varchar2)

    RETURN integer

  IS

  BEGIN
    RETURN (instr (vString, DELIMITER));
  END DelimiterPosition;

BEGIN
  vString := vStringToParse;

  LOOP
    Return_tab (biIndex) := NextWord;
    --
    -- If there are no more elements in the string, return
    -- the table.
    --
    IF (iStringPos = 0) THEN
       RETURN Return_tab;
    END IF;

    Return_tab (biIndex) := substr (vString, 1, (iStringPos - 1));

    biIndex := biIndex + 1;

    --
    -- Chop off the first portion of the string.
    --
    vString := substr (vString, (iStringPos + 1));
  END LOOP;

EXCEPTION
  WHEN VALUE_ERROR THEN
      Log_System_Error (vErrorLocation => 'Parse_String',
                        vErrorText     => SQLERRM);
END;


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