我想在Oracle对象类型中设置默认值，但它需要在构造函数中传递所有属性。
无论如何，我只能在构造函数中传递必需的属性，并且需要默认值。
请参阅以下详细信息
SQL> CREATE TYPE TYPE_SUB AS OBJECT(
2 COL1 NUMBER,
3 COL2 VARCHAR2(100)
4 )
5 NOT FINAL
6 /
Type created.
SQL> CREATE OR REPLACE TYPE TYPE_MAIN
2 UNDER TYPE_SUB
3 (
4 COL3 varchar2(10),
5 COL4 VARCHAR2(10),
6 CONSTRUCTOR FUNCTION TYPE_MAIN(COL1 NUMBER, COL2 VARCHAR2, COL3 varchar2, COL4 VARCHAR2) RETURN SELF AS RESULT)
7 NOT FINAL
8 /
Type created.
SQL> CREATE OR REPLACE TYPE BODY TYPE_MAIN IS
2 CONSTRUCTOR FUNCTION TYPE_MAIN (COL1 NUMBER, COL2 VARCHAR2, COL3 varchar2, COL4 VARCHAR2) RETURN SELF AS RESULT IS
3 BEGIN
4 SELF.COL1 := nvl(COL1,123);
5 SELF.COL2 := nvl(COL2,'NA');
6 SELF.COL3 := nvl(COL3,'NA');
7 SELF.COL4 := nvl(COL4,NULL);
8 RETURN;
9 end;
10 END;
11 /
Type body created.
SQL> CREATE TABLE TAB_MAIN (
2 PKEY NUMBER,
3 COLTEST VARCHAR2(100),
4 COLNEW TYPE_MAIN)
5 /
Table created.
SQL> INSERT INTO TAB_MAIN(PKEY) VALUES(1)
2 /
1 row created.
SQL> INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW) VALUES(1,'TESTCOL',TYPE_MAIN('1','2',NULL,NULL))
2 /
1 row created.
SQL> INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW) VALUES(1,'TESTCOL2',TYPE_MAIN('1',NULL,NULL,NULL))
2 /
1 row created.
SQL> SELECT * FROM TAB_MAIN
2 /
PKEY COLTEST COLNEW(COL1, COL2, COL3, COL4)
---------- ---------- ----------------------------------------
1
1 TESTCOL TYPE_MAIN(1, '2', 'NA', NULL)
1 TESTCOL2 TYPE_MAIN(1, 'NA', 'NA', NULL)
现在，在上面的例子中，如果我只将构造函数中的Col3和Col4属性传递给默认值，那么它就不起作用了。请参阅以下示例。
SQL> CREATE TYPE TYPE_SUB AS OBJECT(
2 COL1 NUMBER,
3 COL2 VARCHAR2(100)
4 )
5 NOT FINAL
6 /
Type created.
SQL> CREATE OR REPLACE TYPE TYPE_MAIN
2 UNDER TYPE_SUB
3 (
4 COL3 varchar2(10),
5 COL4 VARCHAR2(10),
6 CONSTRUCTOR FUNCTION TYPE_MAIN(COL3 varchar2, COL4 VARCHAR2) RETURN SELF AS RESULT)
7 NOT FINAL
8 /
Type created.
SQL> CREATE OR REPLACE TYPE BODY TYPE_MAIN IS
2 CONSTRUCTOR FUNCTION TYPE_MAIN (COL3 varchar2, COL4 VARCHAR2) RETURN SELF AS RESULT IS
3 BEGIN
4 SELF.COL3 := nvl(COL3,'NA');
5 SELF.COL4 := nvl(COL4,NULL);
6 RETURN;
7 end;
8 END;
9 /
Type body created.
SQL> CREATE TABLE TAB_MAIN (
2 PKEY NUMBER,
3 COLTEST VARCHAR2(100),
4 COLNEW TYPE_MAIN)
5 /
Table created.
SQL> INSERT INTO TAB_MAIN(PKEY) VALUES(1)
2 /
1 row created.
SQL> INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW) VALUES(1,'TESTCOL',TYPE_MAIN('1','2',NULL,NULL))
2 /
1 row created.
SQL> INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW) VALUES(1,'TESTCOL2',TYPE_MAIN('1',NULL,NULL,NULL))
2 /
1 row created.
SQL> SELECT * FROM TAB_MAIN
2 /
PKEY COLTEST COLNEW(COL1, COL2, COL3, COL4)
---------- ---------- ----------------------------------------
1
1 TESTCOL TYPE_MAIN(1, '2', NULL, NULL)
1 TESTCOL2 TYPE_MAIN(1, NULL, NULL, NULL)
答案 0 :(得分：5)
在第二个代码块中，您没有调用只有两个参数的构造函数。传递一个null参数并不意味着你使用另一个构造函数，而是使用四个参数调用（默认）构造函数，其中两个参数恰好是故意为null。你有效地做了：
TYPE_MAIN(col1 => '1', col2 => NULL, col3 => NULL, col4 => NULL)
不
TYPE_MAIN(col3 => '1', col4 => NULL)
这样可行：
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW) VALUES(1,'TESTCOL2',TYPE_MAIN('3','4'))
/
...
PKEY COLTEST COLNEW
---------- --------------- --------------------------------------------------
1
1 TESTCOL TYPE_MAIN(1,'2',NULL,NULL)
1 TESTCOL2 TYPE_MAIN(1,NULL,NULL,NULL)
1 TESTCOL2 TYPE_MAIN(NULL,NULL,'3','4')
要使默认值按照我认为您打算在第一个代码块中运行，请在构造函数参数中设置它们，而不是在构造函数的主体中设置它们：
CREATE OR REPLACE TYPE TYPE_MAIN
UNDER TYPE_SUB
(
COL3 varchar2(10),
COL4 VARCHAR2(10),
CONSTRUCTOR FUNCTION TYPE_MAIN(COL1 number default 123,
COL2 VARCHAR2 default 'NA',
COL3 varchar2 default 'NA',
COL4 VARCHAR2 default null) RETURN SELF AS RESULT)
NOT FINAL
/
CREATE OR REPLACE TYPE BODY TYPE_MAIN IS
CONSTRUCTOR FUNCTION TYPE_MAIN (COL1 number default 123,
COL2 VARCHAR2 default 'NA',
COL3 varchar2 default 'NA',
COL4 VARCHAR2 default null) RETURN SELF AS RESULT IS
BEGIN
SELF.COL1 := COL1;
SELF.COL2 := COL2;
SELF.COL3 := COL3;
SELF.COL4 := COL4;
RETURN;
end;
END;
/
然后当只传递其中一个参数时（或者任何时候你没有传递它们，或者你想要从col1开始重写的前几个）你需要命名它，而不是将null传递给其他人，因为这只会覆盖默认值。
INSERT INTO TAB_MAIN(PKEY) VALUES(1)
/
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW)
VALUES(1,'TESTCOL',TYPE_MAIN(1,'2'))
/
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW)
VALUES(1,'TESTCOL2',TYPE_MAIN(1))
/
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW)
VALUES(1,'TESTCOL3',TYPE_MAIN(col3 => '3'))
/
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW)
VALUES(1,'TESTCOL4',TYPE_MAIN(col4 => '4'))
/
PKEY COLTEST COLNEW
---------- --------------- --------------------------------------------------
1
1 TESTCOL TYPE_MAIN(1,'2','NA',NULL)
1 TESTCOL2 TYPE_MAIN(1,'NA','NA',NULL)
1 TESTCOL3 TYPE_MAIN(123,'NA','3',NULL)
1 TESTCOL4 TYPE_MAIN(123,'NA','NA','4')
要同时传递col3和col4，您仍然需要为参数命名，否则它会假设您从col1开始：
INSERT INTO TAB_MAIN(PKEY,COLTEST,COLNEW)
VALUES(1,'TESTCOL5',TYPE_MAIN(col3 => '3', col4 => '4'))
/
PKEY COLTEST COLNEW
---------- --------------- --------------------------------------------------
1
1 TESTCOL TYPE_MAIN(1,'2','NA',NULL)
1 TESTCOL2 TYPE_MAIN(1,'NA','NA',NULL)
1 TESTCOL3 TYPE_MAIN(123,'NA','3',NULL)
1 TESTCOL4 TYPE_MAIN(123,'NA','NA','4')
1 TESTCOL5 TYPE_MAIN(123,'NA','3','4')