练习 DOUBLE INSERT

目标：从一张表取数据插入到另一张表中，此外需要为插入的目标表做一个应用级的日志表，也就是说在插入目标表的同时，还需要将相同的数据插入到日志表中。

在案例一中，我们给出了CREATE TRIGGER；OPEN CURSOR ;BULK INTO VARIABLE; DOUBLE INSERT; INSERT ALL 等方案。每个方案中也阐述了他的优缺点。

其中在DOUBLE INSERT，为了保证数据的一致性，又给出了四种思路，它们分别是锁，串行，临时表和as of 查询。下面将展现这四种思路SQL的展现。

当然DOUBLE INSERT 除了一致性的问题，还有原子性的问题，即有可有目标表和日志表只成功了其它一个，或都没成功。关于原子性的问题。暂不讨论。

1.1思路一锁

Drop table test;

Drop table T_ORG;

DROP TABLE T_LOG;

create table test as select * from all_objects ;

create table T_ORG as select * from all_objects WHERE 1=2;

create table T_LOG as select * from all_objects WHERE 1=2;

# --共享行专用(SRX)：阻止其他事务操作，其会会话不能对test表进行DML操作

SQL> lock table t in exclusive mode nowait;

Locked Object:

OWNEROS_USER_NAME OBJECT_NAME SIDSERIAL# LOCKED_MODE LOGON_TIM

------- ------------- ----------------- ---------- ----------- -------

SYS oracle TEST 18 17 6 26-APR-19

SYS@test>INSERT INTO T_ORG SELECT * FROM TEST;

72183 rows created.

SYS@test>INSERT INTO T_LOG SELECT * FROM TEST;

72183 rows created.

新开一个窗口执行delete 操作产生等待：

SYS@test2>delete from test where OBJECT_ID <10 ;

直到原来窗口事务结束。

SYS@test>COMMIT ;

问题：影响其它事务

1.2思路二串行事务面临的问题 ora-01555

Drop table test;

Drop table T_ORG;

DROP TABLE T_LOG;

create table test as select * from all_objects ;

create table T_ORG as select * from all_objects WHERE 1=2;

create table T_LOG as select * from all_objects WHERE 1=2;

SYS@test>create undo tablespace undotbs datafile '/u01/app/oracle/oradata/test/undotbs.dbf' size 1M ;

Tablespace created.

SYS@test>alter system set undo_tablespace=undotbs;

SYS@test>show parameter undo ;

NAME TYPE VALUE

------------------------------------ ----------- ---------------------

undo_management string AUTO

undo_retention integer 900

undo_tablespace string UNDOTBS

declare

begin

INSERT INTO T_ORG SELECT * FROM TEST;

INSERT INTO T_LOG SELECT * FROM TEST;

Commit ;

end ;

ERROR at line 1:

ORA-30036: unable to extend segment by 8 in undo tablespace 'UNDOTBS'

ORA-06512: at line 3

SYS@test>select count(*) from T_ORG ;

COUNT(*)

----------

问题：UNDO 空间不足时，会报ORA-30036
如果UNDO空间被覆盖会报ORA-01555

1.3思路三临时表

Drop table test;

Drop table T_ORG;

DROP TABLE T_LOG;

create table test as select * from all_objects ;

create table T_ORG as select * from all_objects WHERE 1=2;

create table T_LOG as select * from all_objects WHERE 1=2;

SYS@test>alter system set undo_tablespace=UNDOTBS1;

创建会话级别临时表：

SYS@test> create global temporary table temp1 on
Commit Preserve Rows as select * from
all_objects where 1=2 ;

把数据写入到临时表：

SYS@test>INSERT INTO temp1 SELECT * FROM all_objects;

72186 rows created.

SYS@test>INSERT INTO T_ORG SELECT * FROM temp1;

72186 rows created.

SYS@test>INSERT INTO T_LOG SELECT * FROM temp1;

72186 rows created.

问题：相关于写了三次，读了三次，对性能影响较大

1.4思路四 AS OF 查询

Drop table test;

Drop table T_ORG;

DROP TABLE T_LOG;

create table test as select * from all_objects ;

create table T_ORG as select * from all_objects WHERE 1=2;

create table T_LOG as select * from all_objects WHERE 1=2;

SYS@test>select current_scn from v$database ;

CURRENT_SCN

-----------

975216

SYS@test>INSERT INTO T_ORG SELECT * FROM test as of
scn 975216;

72184 rows created.

SYS@test>INSERT INTO T_LOG SELECT * FROM test as of
scn 975216;

72184 rows created.

前提是你要提前查询SCN 或时间，而且还是查询插入了2次。

针对以上的问题，最好的解决方案是利用ORACLE 的insert all

<wiz_tmp_tag id="wiz-table-range-border" contenteditable="false" style="display: none;">

来自为知笔记(Wiz)