Oracle Externale Tables

Creating External Tables

You create external tables using the CREATE TABLE statement with an ORGANIZATION EXTERNAL clause.

This statement creates only metadata in the data dictionary.

实验:创建外部表并加载数据；

EXAMPLE: Creating an External Table and Loading Data

In this example, the data for the external table resides in the two text files empxt1.dat and empxt2.dat.

The file empxt1.dat contains the following sample data:

数据一：

[oracle@chen test]$ cat empxt1.dat

360,Jane,Janus,ST_CLERK,121,17-MAY-2001,3000,0,50,jjanus

361,Mark,Jasper,SA_REP,145,17-MAY-2001,8000,.1,80,mjasper

362,Brenda,Starr,AD_ASST,200,17-MAY-2001,5500,0,10,bstarr

363,Alex,Alda,AC_MGR,145,17-MAY-2001,9000,.15,80,aalda

The file empxt2.dat contains the following sample data:

数据二：

[oracle@chen test]$ cat empxt2.dat

401,Jesse,Cromwell,HR_REP,203,17-MAY-2001,7000,0,40,jcromwel

402,Abby,Applegate,IT_PROG,103,17-MAY-2001,9000,.2,60,aapplega

403,Carol,Cousins,AD_VP,100,17-MAY-2001,27000,.3,90,ccousins

404,John,Richardson,AC_ACCOUNT,205,17-MAY-2001,5000,0,110,jrichard

创建外部表语句如下：

[root@chen ~]# mkdir /flatfiles/{data,log,bad} -p

[root@chen ~]# chown oracle.oinstall /flatfiles/ -R

[oracle@chen test]$ cat create_external.sql

CONNECT / AS SYSDBA;

— Set up directories and grant access to hr

CREATE OR REPLACE DIRECTORY admin_dat_dir

AS ‘/flatfiles/data’;

CREATE OR REPLACE DIRECTORY admin_log_dir

AS ‘/flatfiles/log’;

CREATE OR REPLACE DIRECTORY admin_bad_dir

AS ‘/flatfiles/bad’;

GRANT READ ON DIRECTORY admin_dat_dir TO hr;

GRANT WRITE ON DIRECTORY admin_log_dir TO hr;

GRANT WRITE ON DIRECTORY admin_bad_dir TO hr;

— hr connects. Provide the user password (hr) when prompted.

CONNECT hr

— create the external table

CREATE TABLE admin_ext_employees

(employee_id NUMBER(4),

first_name VARCHAR2(20),

last_name VARCHAR2(25),

job_id VARCHAR2(10),

manager_id NUMBER(4),

hire_date DATE,

salary NUMBER(8,2),

commission_pct NUMBER(2,2),

department_id NUMBER(4),

email VARCHAR2(25)

)

ORGANIZATION EXTERNAL

(

TYPE ORACLE_LOADER

DEFAULT DIRECTORY admin_dat_dir

ACCESS PARAMETERS

(

records delimited by newline

badfile admin_bad_dir:’empxt%a_%p.bad’

logfile admin_log_dir:’empxt%a_%p.log’

fields terminated by ‘,’

missing field values are null

( employee_id, first_name, last_name, job_id, manager_id,

hire_date char date_format date mask “dd-mon-yyyy”,

salary, commission_pct, department_id, email

)

)

LOCATION (’empxt1.dat’, ’empxt2.dat’)

)

PARALLEL

REJECT LIMIT UNLIMITED;

验证数据

SQL> set linesize 1000

SQL> select * from admin_ext_employees;

EMPLOYEE_ID FIRST_NAME LAST_NAME JOB_ID MANAGER_ID HIRE_DATE SALARY COMMISSION_PCT DEPARTMENT_ID EMAIL

———– ——————– ————————- ———- ———- ——— ———- ————– ————- ————————-

401 Jesse Cromwell HR_REP 203 17-MAY-01 7000 0 40 jcromwel

402 Abby Applegate IT_PROG 103 17-MAY-01 9000 免费云主机域名 .2 60 aapplega

403 Carol Cousins AD_VP 100 17-MAY-01 27000 .3 90 ccousins

404 John Richardson AC_ACCOUNT 205 17-MAY-01 5000 0 110 jrichard

360 Jane Janus ST_CLERK 121 17-MAY-01 3000 0 50 jjanus

361 Mark Jasper SA_REP 145 17-MAY-01 8000 .1 80 mjasper

362 Brenda Starr AD_ASST 200 17-MAY-01 5500 0 10 bstarr

363 Alex Alda AC_MGR 145 17-MAY-01 9000 .15 80 aalda

8 rows selected.

外部表不会在数据库里创建对应的表段；

SQL> select * from user_segments;

no rows selected

外部表只读，不能进行DML操作

SQL> delete admin_ext_employees where employee_id=363;

delete admin_ext_employees where employee_id=363

*

ERROR at line 1:

ORA-30657: operation not supported on external organized table

无法通过analyze收集外部表的统计信息(可以通过dbms_stats收集)

SQL> analyze table admin_ext_employees compute statistics;

analyze table admin_ext_employees compute statistics

*

ERROR at line 1:

ORA-30657: operation not supported on external organized table

SQL> exec dbms_stats.gather_schema_stats(‘HR’);

PL/SQL procedure successfully completed.

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