这就是第三步要教给大家的东西了。
第三步：理解外表数据结构与create table ... organization external语法。大家都用过sqlldr吧？外表的数据文件的结构呢就同sqlldr能读的数据文件结构一样了。那么语法呢？嘿嘿，别急，让我们先来做个sqlldr的练习吧：
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代码:
[oracle@rac1 temp]$ head -10 userlist.txt
1,"RudolfLu"
3,"tomgu"
6,"coug"
7,"chao_ping"
8,"parrotao"
9,"cnoug"
10,"FilsDeDragon"
11,"Dragon"
15,"Xavier"
[oracle@rac1 temp]$ cat user.ctl
LOAD
INFILE '/home/oracle/temp/userlist.txt'
badfile '/home/oracle/temp/userlist.bad'
discardfile '/home/oracle/temp/userlist.dis'
APPEND
INTO TABLE userlist
fields terminated by ',' optionally enclosed by '"'
trailing nullcols
( id char(30),
username char(30)
)
rudolf@TEST>create table userlist
2 (id number,
3 username varchar2(30)
4 );
Table created.
rudolf@TEST>!
[oracle@rac1 temp]$ sqlldr rudolf/nix@test2.world control=./user.ctl external_table=GENERATE_ONLY
注意，我们加了一个external_table的参数。它的作用是告诉sqlldr不用真实load数据，而是生成包含external table 创建脚本的log文件。
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代码:
[oracle@rac1 temp]$ ls
user.ctl userlist.txt user.log
[oracle@rac1 temp]$ cat user.log
SQL*Loader: Release 9.2.0.4.0 - Production on Wed Dec 10 20:50:19 2003
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Control File: ./user.ctl
Data File: /home/oracle/temp/userlist.txt
Bad File: /home/oracle/temp/userlist.bad
Discard File: /home/oracle/temp/userlist.dis
...
CREATE DIRECTORY statements needed for files
------------------------------------------------------------------------
CREATE DIRECTORY SYS_SQLLDR_XT_TMPDIR_00000 AS '/home/oracle/temp/'
CREATE TABLE statement for external table:
------------------------------------------------------------------------
CREATE TABLE "SYS_SQLLDR_X_EXT_USERLIST"
(
ID NUMBER,
USERNAME VARCHAR2(30)
)
ORGANIZATION external
(
TYPE oracle_loader
DEFAULT DIRECTORY SYS_SQLLDR_XT_TMPDIR_00000
ACCESS PARAMETERS
(
RECORDS DELIMITED BY NEWLINE CHARACTERSET US7ASCII
BADFILE 'SYS_SQLLDR_XT_TMPDIR_00000':'userlist.bad'
DISCARDFILE 'SYS_SQLLDR_XT_TMPDIR_00000':'userlist.dis'
LOGFILE 'user.log_xt'
READSIZE 1048576
FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' LDRTRIM
MISSING FIELD VALUES ARE NULL
REJECT ROWS WITH ALL NULL FIELDS
(
ID CHAR(30)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"',
USERNAME CHAR(30)
TERMINATED BY "," OPTIONALLY ENCLOSED BY '"' )
)
location
(
'userlist.txt'
)
)REJECT LIMIT UNLIMITED
...
瞧，原来我们更本不用担心怎么写create external table的语句呢。sqlldr就可以帮我们生成了！
您是不是已经学会了？
