oracle 12c 列自增长 identity column

-- 针对mssql，mysql的列子增长优势，oracle12c实现了数据库的列自增长功能，其实内部还是用序列来实现的，
SQL> alter session set container=pdb1;

会话已更改。

SQL> alter session set container=cdb$root;
ERROR:
ORA-01031: 权限不足

SQL> select count(1) from user_objects;

COUNT(1)
----------
0

SQL> create table t1(id number GENERATED AS IDENTITY,name varchar2(10));

表已创建。

SQL> select object_name,object_type from user_objects;

OBJECT_NAME
------------------------------------------------------------------------------

OBJECT_TYPE
----------------------------------------------
T1
TABLE

ISEQ$$_92786
SEQUENCE

SQL> set long 500
SQL> select dbms_metadata.get_ddl('TABLE','T1') from dual;

DBMS_METADATA.GET_DDL('TABLE','T1')
------------------------------------------------------------------------------

CREATE TABLE "LOGE"."T1"
(    "ID" NUMBER GENERATED ALWAYS AS IDENTITY MINVALUE 1 MAXVALUE 999999999
999
99999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOT NULL

NABLE,          "NAME" VARCHAR2(10)
) SEGMENT CREATION DEFERRED
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
TABLESPACE "USERS"

SQL> insert into t1 values('china');
insert into t1 values('china')
*
第 1 行出现错误:
ORA-00947: 没有足够的值

SQL> insert into t1(name) values('china');

已创建 1 行。

SQL> commit;

提交完成。

SQL> select * from t1;

ID NAME
---------- --------------------
1 china

SQL> insert into t1 values(2,'usa');
insert into t1 values(2,'usa')
*
第 1 行出现错误:
ORA-32795: 无法插入到“始终生成”身份列

SQL> update t1 set id=100 ;
update t1 set id=100
*
第 1 行出现错误:
ORA-32796: 无法更新“始终生成”身份列

SQL> select value from v$diag_info where name='Default Trace File';

VALUE
------------------------------------------------------------------------------

G:\APP\ORACLE\diag\rdbms\orcl\orcl\trace\orcl_ora_7744.trc

SQL> alter session set events '10046 trace name context forever,level 12';

会话已更改。

SQL> insert into t1 (name) values('Japan');

已创建 1 行。

SQL> commit;

提交完成。

SQL> alter session set events '10046 trace name context off';

会话已更改。

-- 查看
PARSING IN CURSOR #523432848 len=37 dep=0 uid=110 oct=2 lid=110 tim=92491773830 hv=1360139914 ad='7ff7ae59e50' sqlid='37wwf9j8j45na'
insert into t1 (name) values('Japan')
END OF STMT
PARSE #523432848:c=0,e=76132,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=4015265140,tim=92491773828
EXEC #523432848:c=0,e=11550,p=0,cr=1,cu=5,mis=0,r=1,dep=0,og=1,plh=4015265140,tim=92491785524
STAT #523432848 id=1 cnt=0 pid=0 pos=1 obj=0 op='LOAD TABLE CONVENTIONAL  T1 (cr=1 pr=0 pw=0 time=11469 us)'
STAT #523432848 id=2 cnt=1 pid=1 pos=1 obj=92787 op='SEQUENCE  ISEQ$$_92786 (cr=0 pr=0 pw=0 time=11142 us)'
WAIT #523432848: nam='SQL*Net message to client' ela= 5 driver id=1413697536 #bytes=1 p3=0 obj#=-1 tim=92491785935

--修改属性
SQL> alter table t1 modify (id number generated as identity minvalue 1 maxvalue
999999 increment by 2 start with 1 cache 10);

表已更改。

-- 另外还有GENERATED BY DEFAULT AS IDENTITY、GENERATED BY DEFAULT ON NULL AS IDENTITY属性

-- 2，12c之前实现方式
SQL> drop table t2 purge;

表已删除。

SQL> create table t2 (id int,name varchar2(10));

表已创建。

SQL> create sequence seq_t2
2  increment by 1 minvalue 1 maxvalue 9999999999 start with 1 cache 10 order;

序列已创建。

SQL> create trigger t_t2
2  before insert on t2
3  for each row
4  begin
5  select seq_t2.nextval into :new.id from dual;
6  end;
7  /

触发器已创建

SQL> insert into t2(name) values('china');

已创建 1 行。

SQL> commit;

提交完成。

SQL> insert into t2(name) values('china');

已创建 1 行。

SQL> select * from t2;

ID NAME
---------- --------------------
1 china
2 china