[轉(zhuǎn)自：http://space.itpub.net/519536/viewspace-631445]

當(dāng)使用IMPDP完成數(shù)據(jù)庫導(dǎo)入時，如遇到表已存在時，Oracle提供給我們?nèi)缦滤姆N處理方式：
a.忽略（SKIP，默認(rèn)行為）；
b.在原有數(shù)據(jù)基礎(chǔ)上繼續(xù)增加（APPEND）；
c.先DROP表，然后創(chuàng)建表，最后完成數(shù)據(jù)插入（REPLACE）；
d.先TRUNCATE，再完成數(shù)據(jù)插入（TRUNCATE）。

真實感受一下這幾種方式的效果，供參考。

1.IMPDP在線幫助中關(guān)于TABLE_EXISTS_ACTION參數(shù)的描述
TABLE_EXISTS_ACTION ? Action to take if imported object already exists.
? ? ? ? ? ? ? ? ? ? ? Valid keywords: (SKIP), APPEND, REPLACE and TRUNCATE.

2.Oracle官方文檔中的描述
http://download.oracle.com/docs/cd/B19306_01/server.102/b14215/dp_import.htm#sthref365
Oracle官方文檔是根本，需研讀。

3.使用EXPDP生成一份dump文件
sec@secDB /expdp$ expdp sec/sec directory=expdp_dir dumpfile=`date +"%Y%m%d%H%M%S"`_sec.dmp logfile=`date +"%Y%m%d%H%M%S"`_sec.log

Export: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:29:17

Copyright (c) 2003, 2005, Oracle. ?All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Starting "SEC"."SYS_EXPORT_SCHEMA_01": ?sec/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec.log
Estimate in progress using BLOCKS method...
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 3 MB
Processing object type SCHEMA_EXPORT/USER
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
Processing object type SCHEMA_EXPORT/TABLE/INDEX/INDEX
Processing object type SCHEMA_EXPORT/TABLE/CONSTRAINT/CONSTRAINT
Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS
Processing object type SCHEMA_EXPORT/TABLE/COMMENT
. . exported "SEC"."T" ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 2.259 MB ? 24360 rows
Master table "SEC"."SYS_EXPORT_SCHEMA_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SEC.SYS_EXPORT_SCHEMA_01 is:
? /expdp/20100401102917_sec.dmp
Job "SEC"."SYS_EXPORT_SCHEMA_01" successfully completed at 10:29:20

4.分別使用四中方式真實的感知一下具體效果
用到的IMPDP語句統(tǒng)一匯總在這里，方便參考。
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=SKIP
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE
impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE

1）默認(rèn)行為SKIP
sec@ora10g> select count(*) from t;

? COUNT(*)
----------
? ? ?24360

sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:50:41

Copyright (c) 2003, 2005, Oracle. ?All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": ?system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39151: Table "SEC"."T" exists. All dependent metadata and data will be skipped due to table_exists_action of skip
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:50:42

上面的行為與下面一條顯示的指定“SKIP”效果是一樣的，不贅述。
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=SKIP

2）APPEND方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:51:32

Copyright (c) 2003, 2005, Oracle. ?All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": ?system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=APPEND
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39152: Table "SEC"."T" exists. Data will be appended to existing table but all dependent metadata will be skipped due to table_exists_action of append
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T" ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 2.259 MB ? 24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:51:33

此時表T的記錄數(shù)翻倍。
sec@ora10g> select count(*) from t;

? COUNT(*)
----------
? ? ?48720

3）REPLACE方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:54:28

Copyright (c) 2003, 2005, Oracle. ?All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": ?system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=REPLACE
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T" ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 2.259 MB ? 24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 1 error(s) at 10:54:29

sec@ora10g> select count(*) from t;

? COUNT(*)
----------
? ? ?24360

4）TRUNCATE方式
sec@secDB /expdp$ impdp system/sys directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE

Import: Release 10.2.0.3.0 - 64bit Production on Thursday, 01 April, 2010 10:54:55

Copyright (c) 2003, 2005, Oracle. ?All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
Master table "SYSTEM"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_FULL_01": ?system/******** directory=expdp_dir dumpfile=20100401102917_sec.dmp logfile=20100401102917_sec_impdp.log TABLE_EXISTS_ACTION=TRUNCATE
Processing object type SCHEMA_EXPORT/USER
ORA-31684: Object type USER:"SEC" already exists
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
ORA-39153: Table "SEC"."T" exists and has been truncated. Data will be loaded but all dependent metadata will be skipped due to table_exists_action of truncate
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
. . imported "SEC"."T" ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 2.259 MB ? 24360 rows
Job "SYSTEM"."SYS_IMPORT_FULL_01" completed with 2 error(s) at 10:54:56

sec@ora10g> select count(*) from t;

? COUNT(*)
----------
? ? ?24360

5.小結(jié)
IMPDP的TABLE_EXISTS_ACTION參數(shù)相比IMP工具是一個進(jìn)步，我們的控制手段得到加強(qiáng)，莫要固步自封。

Good luck.

secooler
10.04.06

-- The End --

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