Oracle TYPE OBJECT详解(二)
e_id is NULL #1');
END IF;
emp.employee_id := 330;
IF emp IS NULL THEN DBMS_OUTPUT.PUT_LINE('emp is NULL #2'); END IF;
IF emp.employee_id IS NULL THEN
DBMS_OUTPUT.PUT_LINE('emp.employee_id is NULL #2');
END IF;
emp := employee_typ(NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL,
address_typ(NULL, NULL, NULL, NULL));
-- emp := NULL; -- this would have made the following IF statement TRUE
IF emp IS NULL THEN DBMS_OUTPUT.PUT_LINE('emp is NULL #3'); END IF;
IF emp.employee_id IS NULL THEN
DBMS_OUTPUT.PUT_LINE('emp.employee_id is NULL #3');
END IF;
EXCEPTION
WHEN ACCESS_INTO_NULL THEN
DBMS_OUTPUT.PUT_LINE('Cannot assign value to NULL object');
END;
5. 在PL/SQL中操纵对象：
5.1.调用对象构造器和方法（Calling Object Constructors and Methods）
[sql]
DECLARE
emp employee_typ;
BEGIN
INSERT INTO employee_tab VALUES (employee_typ(310, 'Evers', 'Boston', 'EBOSTON',
'555.111.2222', to_date('2012-12-24', 'yyyy-mm-dd'), 'SA_REP', 9000, .15, 101, 110,
address_typ('123 Main', 'San Francisco', 'CA', '94111')) );
INSERT INTO employee_tab VALUES (employee_typ(320, 'Martha', 'Dunn', 'MDUNN',
'555.111.3333', to_date('2012-11-5', 'yyyy-mm-dd'), 'AC_MGR', 12500, 0, 101, 110,
address_typ('123 Broadway', 'Redwood City', 'CA', '94065')) );
END;
5.2 更新和删除对象：
[sql]
DECLARE
emp employee_typ;
BEGIN
INSERT INTO employee_tab VALUES (employee_typ(370, 'Robert', 'Myers', 'RMYERS',
'555.111.2277', to_date('2012-3-7', 'yyyy-mm-dd'), 'SA_REP', 8800, .12, 101, 110,
address_typ('540 Fillmore', 'San Francisco', 'CA', '94011')) );
UPDATE employee_tab e SET e.address.street = '1040 California'
WHERE e.employee_id = 370;
DELETE FROM employee_tab e WHERE e.employee_id = 310;
END;
6. 通过REF修饰符操纵对象：
[sql]
DECLARE
emp employee_typ;
emp_ref REF employee_typ;
emp_name VARCHAR2(50);
BEGIN
SELECT REF(e) INTO emp_ref FROM employee_tab e WHERE e.employee_id = 370;
-- the following assignment raises an error, not allowed in PL/SQL
-- emp_name := emp_ref.first_name || ' ' || emp_ref.last_name;
-- emp := DEREF(emp_ref); not allowed, cannot use DEREF in procedural statements
SELECT DEREF(emp_ref) INTO emp FROM DUAL; -- use dummy table DUAL
emp_name := emp.first_name || ' ' || emp.last_name;
DBMS_OUTPUT.PUT_LINE(emp_name);
END;
7. 定义相当于PL/SQL集合类型的SQL类型（Defining SQL Types Equivalent to PL/SQL Collection Types）
7.1 定义嵌套表：
--建嵌套表类型
CREATE TYPE CourseList AS TABLE OF VARCHAR2(10) -- define type
--建对象类型
CREATE TYPE student AS OBJECT ( -- create object
id_num INTEGER(4),
name VARCHAR2(25),
address VARCHAR2(35),
status CHAR(2),
courses CourseList); -- declare nested table as attribute
--建立嵌套表类型表
CREATE TABLE sophomores of student
NESTED TABLE courses STORE AS courses_nt;
--插入数据
insert into sophomores
values(1,'dylan','CARL STREET','ACTIVE',
CourseList('MATH1020')
);
--查询
SELECT a.*, b.*
from sophomores a, TABLE(a.courses) b;
select /*+ nested_table_get_refs */ *
from courses_nt t;
7.2 定义数组：
-- 声明数组类型（Each project has a 16-character code name）