如何在oracle中声明队列数据结构？

Question

有没有办法声明在Oracle或特定架构中可以全局访问的队列数据结构？
在全球范围内，我意味着可以访问所有数据库或特定模式的程序

编辑：
我发现我可以通过包装制作FIFO QUEUE。所以我写了一个代码，但我得到了错误。任何人都知道我为什么会收到这个错误？ 包规格：

CREATE OR REPLACE PACKAGE HR.TEST_PACKAGE IS
  PROCEDURE ADDQ (TABLE_NAME VARCHAR2);
  FUNCTION DELQ RETURN VARCHAR2;
END TEST_PACKAGE;
/

包体：

CREATE OR REPLACE PACKAGE BODY HR.TEST_PACKAGE IS
  REAR NUMBER := 0;
  FRONT NUMBER := 0;
  TYPE QUEUE_TYPE IS VARRAY(10) OF VARCHAR2(15);
  QUEUE_ARRAY QUEUE_TYPE;
PROCEDURE ADDQ (TABLE_NAME VARCHAR2) IS
BEGIN
  REAR := (REAR+1) MOD 10;
  IF (REAR = 0) THEN
    REAR := 10;
  END IF;
  QUEUE_ARRAY(REAR) := TABLE_NAME;
END ADDQ;
FUNCTION DELQ RETURN VARCHAR2 IS
BEGIN
  IF (FRONT = REAR) THEN
    RETURN 'EMPTY';
  ELSE
    FRONT := (FRONT + 1) MOD 10;
    IF (FRONT = 0) THEN
      front := 10;
    END IF;
    RETURN QUEUE_ARRAY(FRONT);
  END IF;
END DELQ;
END TEST_PACKAGE;
/

当我运行此示例代码时：

create or replace procedure hr.test is
begin
  hr.test_package.addq('a');
  hr.test_package.addq('b');
  dbms_output.put_line(hr.test_package.delq);
end test;

我收到此错误：

ORA-06531: Reference to uninitialized collection
06531. 00000 -  "Reference to uninitialized collection"
*Cause:    An element or member function of a nested table or varray
           was referenced (where an initialized collection is needed)
           without the collection having been initialized.
*Action:   Initialize the collection with an appropriate constructor
           or whole-object assignment.

当想要运行代码的这一部分时会发生此错误：

QUEUE_ARRAY(REAR) := TABLE_NAME;  

Answer 1

解决了问题。以下代码将在oracle中声明FIFO队列 addq过程将插入队列中，delq函数将删除并从队列中返回一个值 包规格：

CREATE OR REPLACE PACKAGE HR.TEST_PACKAGE IS
  PROCEDURE ADDQ (TABLE_NAME VARCHAR2);
  FUNCTION DELQ RETURN VARCHAR2;
END TEST_PACKAGE;
/

包体：

CREATE OR REPLACE PACKAGE BODY HR.TEST_PACKAGE IS
  REAR NUMBER := 0;
  FRONT NUMBER := 0;
  TYPE QUEUE_TYPE IS VARRAY(10) OF VARCHAR2(15);
  QUEUE_ARRAY QUEUE_TYPE := QUEUE_TYPE() ;
PROCEDURE ADDQ (TABLE_NAME VARCHAR2) IS
BEGIN
  REAR := (REAR+1) MOD 10;
  IF (REAR = 0) THEN
    REAR := 10;
  END IF;
  QUEUE_ARRAY.EXTEND;
  QUEUE_ARRAY(REAR) := TABLE_NAME;
END ADDQ;
FUNCTION DELQ RETURN VARCHAR2 IS
BEGIN
  IF (FRONT = REAR) THEN
    RETURN 'EMPTY';
  ELSE
    FRONT := (FRONT + 1) MOD 10;
    IF (FRONT = 0) THEN
      front := 10;
    END IF;
    RETURN QUEUE_ARRAY(FRONT);
  END IF;
END DELQ;
END TEST_PACKAGE;
/