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 .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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