DBMS_METADATA中使用SESSION_TRANSFORM过滤不想获取的DDL

我们一般使用dbms_metadata.get_ddl获取对象的ddl的时候，有时会获取一些其他额外的信息，例如当你想获取表的创建语句的时候，你会得到表的约束信息，这个信息可能是你不想要的，那么就可以用SESSION_TRANSFORM对它进行过滤。

看下面的示例，创建一个有主键和外键的表，获取他的ddl语句：

SQL> CREATE TABLE tb1 (id int primary key);
 
Table created.
 
SQL> create table tb2 (id int primary key references tb1(id));
 
Table created.
SQL> insert into tb1 values(1);
 
1 row created.
 
SQL> commit;
 
Commit complete.
 
SQL> insert into tb2 values(1);
 
1 row created.
 
SQL> commit;
 
SQL>  select dbms_metadata.get_ddl('TABLE','TB2','TEST') from dual;
 
DBMS_METADATA.GET_DDL('TABLE','TB2','TEST')
--------------------------------------------------------------------------------
 
  CREATE TABLE "TEST"."TB2"
   (	"ID" NUMBER(*,0),
	 PRIMARY KEY ("ID")
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DE
FAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "USERS"  ENABLE,
	 FOREIGN KEY ("ID")
	  REFERENCES "TEST"."TB1" ("ID") ENABLE
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DE
FAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "USERS"

不单单是获取到了创建的基本字段的语句，还有主键，约束，外键，存储参数，表空间等，如果这些你不需要，都是可以进行过滤的，例如我过滤掉主键、外键、存储信息

使用如下语句：

exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,‘REF_CONSTRAINTS’,false);
exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,‘CONSTRAINTS’,false);
exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,‘STORAGE’,false);

exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,'REF_CONSTRAINTS',false);
 
PL/SQL procedure successfully completed.
 
exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,'CONSTRAINTS',false);
 
PL/SQL procedure successfully completed.
 
SQL> exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,'STORAGE',false);
 
PL/SQL procedure successfully completed.
 
SQL> 
SQL>  select dbms_metadata.get_ddl('TABLE','TB2','TEST') from dual;
 
DBMS_METADATA.GET_DDL('TABLE','TB2','TEST')
--------------------------------------------------------------------------------
 
  CREATE TABLE "TEST"."TB2"
   (	"ID" NUMBER(*,0)
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  TABLESPACE "USERS"

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