外部表在Oracle 9i中引入，外部表的特性是对现有SQL*Loader功能的补充，它可以使您访问外部数据源中的数据，就像访问数据库中的表同样。本篇就Oracle 12c中的外部表进行总结和演示，演示环境为Oracle Database 12c Enterprise Edition Release 12.1.0.2.0。sql
1 外部表介绍外部表是经过create table ... organization external语句建立的，当建立外部表时，需指定以下属性：数据库
外部表的建立能够经过两种访问驱动实现，下面将分别介绍。服务器
SQL> ho mkdir /home/oracle/ext SQL> create directory ext_dir as '/home/oracle/ext'; Directory created. SQL> grant read,write on directory ext_dir to alen; Grant succeeded.
建立外部表时若是数据文件不是文本文件，则须要使用preprocessor子句。oracle
1）建立测试数据app
[oracle@odd ext]$ cat emp.dat "EMPNO","ENAME","JOB","MGR","HIREDATE","SAL","COMM","DEPTNO" "7369","SMITH","CLERK","7902","1980/12/17","800.00","","20" "7499","ALLEN","SALESMAN","7698","1981/2/20","1600.00","300.00","30" "7521","WARD","SALESMAN","7698","1981/2/22","1250.00","500.00","30" "7566","JONES","MANAGER","7839","1981/4/2","2975.00","","20" "7654","MARTIN","SALESMAN","7698","1981/9/28","1250.00","1400.00","30" "7698","BLAKE","MANAGER","7839","1981/5/1","2850.00","","30" "7782","CLARK","MANAGER","7839","1981/6/9","2450.00","","10" "7788","SCOTT","ANALYST","7566","1987/4/19","3000.00","","20" "7839","KING","PRESIDENT","","1981/11/17","5000.00","","10" "7844","TURNER","SALESMAN","7698","1981/9/8","1500.00","0.00","30" "7876","ADAMS","CLERK","7788","1987/5/23","1100.00","","20" "7900","JAMES","CLERK","7698","1981/12/3","950.00","","30" "7902","FORD","ANALYST","7566","1981/12/3","3000.00","","20" "7934","MILLER","CLERK","7782","1982/1/23","1300.00","","10"
2）建立外部表ide
SQL> conn alen/alen@odd
Connected.
SQL> ho cat /home/oracle/ext/emp.sql
create table emp
(
empno number(4),
ename varchar2(10),
job varchar2(9),
mgr number(4),
hiredate date,
sal number(7,2),
comm number(7,2),
deptno number(2)
)
organization external --指定建立的表是外部表
(
type oracle_loader --外部表访问驱动类型
default directory ext_dir --默认目录，需提早建立
access parameters --设置访问参数，注意前后顺序，不然出错
(
records delimited by newline
badfile ext_dir:'emp.bad'
discardfile ext_dir:'emp.dsc'
logfile ext_dir:'emp.log'
field names all files ignore
fields terminated by ',' optionally enclosed by '"' ldrtrim
reject rows with all null fields
(empno,
ename,
job,
mgr,
hiredate char(10) date_format date mask 'yyyy-mm-dd',
sal,
comm,
deptno
))
location('emp.dat')
)reject limit unlimited;
SQL> @emp.sql
Table created.
SQL> set linesize 200
SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
14 rows selected.
外部表能够手动写SQL，也可使用sqlldr工具生成外部表，下面是具体建立过程。工具
1）建立控制文件测试
[oracle@odd ext]$ cat alen.ctl load data field names all files ignore infile 'emp.dat' badfile 'emp.bad' discardfile 'emp.dsc' into table alen fields terminated by ',' optionally enclosed by '"' (empno, ename, job, mgr, hiredate date 'yyyy-mm-dd', sal, comm, deptno )
2）sqlldr利用generate_only生成外部表this
[oracle@odd ext]$ sqlldr alen/alen@odd control=alen.ctl external_table=generate_only log=alen.log SQL*Loader: Release 12.1.0.2.0 - Production on Wed May 13 22:08:47 2020 Copyright (c) 1982, 2014, Oracle and/or its affiliates. All rights reserved. Path used: External Table
3）查看日志日志
[oracle@odd ext]$ cat alen.log
SQL*Loader: Release 12.1.0.2.0 - Production on Wed May 13 22:08:47 2020
Copyright (c) 1982, 2014, Oracle and/or its affiliates. All rights reserved.
Control File: alen.ctl
Data File: emp.dat
Bad File: emp.bad
Discard File: emp.dsc
(Allow all discards)
Number to load: ALL
Number to skip: 0
Errors allowed: 50
Continuation: none specified
Path used: External Table
Table ALEN, loaded from every logical record.
Insert option in effect for this table: INSERT
Column Name Position Len Term Encl Datatype
------------------------------ ---------- ----- ---- ---- ---------------------
EMPNO FIRST * , O(") CHARACTER
ENAME NEXT * , O(") CHARACTER
JOB NEXT * , O(") CHARACTER
MGR NEXT * , O(") CHARACTER
HIREDATE NEXT * , O(") DATE 'yyyy-mm-dd'
SAL NEXT * , O(") CHARACTER
COMM NEXT * , O(") CHARACTER
DEPTNO NEXT * , O(") CHARACTER
CREATE TABLE statement for external table:
------------------------------------------------------------------------
CREATE TABLE "SYS_SQLLDR_X_EXT_ALEN"
(
"EMPNO" NUMBER(4),
"ENAME" VARCHAR2(10),
"JOB" VARCHAR2(9),
"MGR" NUMBER(4),
"HIREDATE" DATE,
"SAL" NUMBER(7,2),
"COMM" NUMBER(7,2),
"DEPTNO" NUMBER(2)
)
ORGANIZATION external
(
TYPE oracle_loader
DEFAULT DIRECTORY EXT_DIR
ACCESS PARAMETERS
(
RECORDS DELIMITED BY NEWLINE CHARACTERSET US7ASCII
BADFILE 'EXT_DIR':'emp.bad'
DISCARDFILE 'EXT_DIR':'emp.dsc'
LOGFILE 'alen.log_xt'
READSIZE 1048576
FIELD NAMES ALL FILES IGNORE
FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' LDRTRIM
REJECT ROWS WITH ALL NULL FIELDS
(
"EMPNO" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"ENAME" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"JOB" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"MGR" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"HIREDATE" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"'
DATE_FORMAT DATE MASK 'yyyy-mm-dd',
"SAL" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"COMM" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
"DEPTNO" CHAR(255)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"'
)
)
location
(
'emp.dat'
)
)REJECT LIMIT UNLIMITED
INSERT statements used to load internal tables:
------------------------------------------------------------------------
INSERT /*+ append */ INTO ALEN
(
EMPNO,
ENAME,
JOB,
MGR,
HIREDATE,
SAL,
COMM,
DEPTNO
)
SELECT
"EMPNO",
"ENAME",
"JOB",
"MGR",
"HIREDATE",
"SAL",
"COMM",
"DEPTNO"
FROM "SYS_SQLLDR_X_EXT_ALEN"
statements to cleanup objects created by previous statements:
------------------------------------------------------------------------
DROP TABLE "SYS_SQLLDR_X_EXT_ALEN"
Run began on Wed May 13 22:08:47 2020
Run ended on Wed May 13 22:08:47 2020
Elapsed time was: 00:00:00.47
CPU time was: 00:00:00.01
4）利用上述sql建立外部表SQL
[oracle@odd ext]$ cat alen.sql CREATE TABLE alen ( "EMPNO" NUMBER(4), "ENAME" VARCHAR2(10), "JOB" VARCHAR2(9), "MGR" NUMBER(4), "HIREDATE" DATE, "SAL" NUMBER(7,2), "COMM" NUMBER(7,2), "DEPTNO" NUMBER(2) ) ORGANIZATION external ( TYPE oracle_loader DEFAULT DIRECTORY EXT_DIR ACCESS PARAMETERS ( RECORDS DELIMITED BY NEWLINE CHARACTERSET US7ASCII BADFILE 'EXT_DIR':'emp.bad' DISCARDFILE 'EXT_DIR':'emp.dsc' LOGFILE 'alen.log_xt' READSIZE 1048576 FIELD NAMES ALL FILES IGNORE FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' LDRTRIM REJECT ROWS WITH ALL NULL FIELDS ( "EMPNO" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "ENAME" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "JOB" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "MGR" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "HIREDATE" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' DATE_FORMAT DATE MASK 'yyyy-mm-dd', "SAL" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "COMM" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"', "DEPTNO" CHAR(255) TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' ) ) location ( 'emp.dat' ) )REJECT LIMIT UNLIMITED
5）删除原alen表，建立外部表并验证
SQL> drop table alen; Table dropped. SQL> @alen.sql 51 ; Table created. SQL> select count(1) from alen; COUNT(1) ---------- 14
建立外部表，除了使用ORACLE_LOADER驱动以外，还可使用ORACLE_DATAPUMP，使用ORACLE_DATAPUMP能够实现数据的卸载和加载，经过create table as select 语句，ORACLE_DATAPUMP驱动能够将数据写到一个二进制的dump文件中，但该文件只能经过ORACLE_DATAPUMP访问驱动进行访问，并且，该文件一旦建立，不能被修改，能够被屡次读取。
1）建立测试数据
SQL> conn alen/alen@odd Connected. SQL> create table dept as select * from scott.dept; Table created. SQL> select * from dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON
2）CTAS方式建立外部表
SQL> ho cat /home/oracle/ext/dept.sql
create table dept_xt
organization external
(
type oracle_datapump
default directory ext_dir
location('dept_xt.dump')
)
as select * from dept;
SQL> @/home/oracle/ext/dept.sql
Table created.
3）查看表及dump文件
SQL> select * from dept_xt; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL>ho ls /home/oracle/ext/dept_xt.dump /home/oracle/ext/dept_xt.dump
4）修改外部表，出错，即不能进行修改数据
SQL> update dept_xt set loc='SZ' where deptno=10; update dept_xt set loc='SZ' where deptno=10 * ERROR at line 1: ORA-30657: operation not supported on external organized table
能够利用上面建立的dump文件建立新的外部表。
1）利用dump文件建立外部表，location位置能够指定多个dump文件
SQL> ho cat /home/oracle/ext/alen_xt.sql
create table alen_xt
(
deptno number(2),
dname varchar2(14),
loc varchar2(13)
)
organization external
(
type oracle_datapump
default directory ext_dir
location('dept_xt.dump')
)
;
SQL> @/home/oracle/ext/alen_xt.sql
Table created.
2）查看数据
SQL> select * from alen_xt; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON
经过上面的介绍和演示，能够看出，外部表在使用上有很大的优点，尤为是在批量处理外部数据的时候。