　　在日常工作中；经常会遇到这样的需求：

- oracle 数据表跟文本或者文件格式进行交互；即将指定文件内容导入对应的 oracle 数据表中；或者从 oracle 数据表导出。
- 其他数据库中的表跟oracle数据库进行交互。

　　若是少量数据；可选择的解决方案有很多。常用的用 pl/sql developer工具，或者手动转换为 insert 语句，或者通过api。但数据量大；用上面的方法效率太烂了。本文来说说 oracle 数据的加载和卸载。

- oracle中的dblink
- oracle加载数据-外部表
- oracle加载数据-sqlldr工具
- oracle卸载数据-sqludr

一. oracle 中的 dblink

　　在日常工作中；会遇到不同的数据库进行数据对接；每个数据库都有着功能；像oracle有 dblink ; postgresql有外部表。

1.1 oracle dblink 语法

create [public] database link link 
connect to username 
identified by password
using 'connectstring'

1.2 oracle to mysql

二.oracle加载数据-外部表

　　oracle外部表用来存取数据库以外的文本文件（text file）或oracle专属格式文件。因此，建立外部表时不会产生段、区、数据块等存储结构，只有与表相关的定义放在数据字典中。外部表，顾名思义，存储在数据库外面的表。当存取时才能从oracle专属格式文件中取得数据，外部表仅供查询，不能对外部表的内容进行修改（insert、update、delete操作）。不能对外部表建立索引。

2.1 创建外部表需要的目录

# 创建外部表需要的目录
sql> create or replace directory dump_dir as '/data/ora_ext_lottu'; 

directory created.
# 给用户授予指定目录的操作权限
sql> grant read,write on directory dump_dir to lottu;

grant succeeded.

2.2 外部表源文件lottu.txt

10,accounting,new york
20,research,dallas
30,sales,chicago
40,operations,boston

2.3 创建外部表

drop table dept_external purge;

create table dept_external (
   deptno     number(6),
   dname      varchar2(20),
   loc        varchar2(25) 
)
organization external
(type oracle_loader
 default directory dump_dir
 access parameters
 (
  records delimited by newline
  badfile 'lottu.bad'
  logfile 'lottu.log'
  fields terminated by ","  optionally enclosed by '"'
  (
   deptno     integer external(6),
   dname      char(20),
   loc        char(25)
  )
 )
 location ('lottu.txt')
)
reject limit unlimited;

查看数据

sql> select * from dept_external;

    deptno dname  loc
---------- -------------------- -------------------------
 10 accounting  new york
 20 research  dallas
 30 sales  chicago
 40 operations  boston

三. oracle加载数据-sqlldr工具

3.1 准备实验对象

　　创建文件lottu.txt；和表tbl_load_01。

[oracle@oracle235 ~]$ seq 1000|awk -vofs="," '{print $1,"lottu",systime()-$1}' > lottu.txt
[oracle@oracle235 ~]$ sqlplus lottu/li0924

sql*plus: release 11.2.0.4.0 production on mon aug 13 22:58:34 2018

copyright (c) 1982, 2013, oracle.  all rights reserved.


connected to:
oracle database 11g enterprise edition release 11.2.0.4.0 - 64bit production
with the partitioning, olap, data mining and real application testing options

sql> create table tbl_load_01 (id number,name varchar2(10),accountid number);

table created.

3.2 创建控制文件lottu.ctl

load data
characterset utf8
        infile '/home/oracle/lottu.txt'
        truncate into table tbl_load_01
        fields terminated by ','
        trailing nullcols
  optionally enclosed by ' ' trailing nullcols
(
 id ,
 name,
 accountid
)

3.3 执行sqlldr

[oracle@oracle235 ~]$ sqlldr 'lottu/"li0924"' control=/home/oracle/lottu.ctl log=/home/oracle/lottu.log bad=/home/oracle/lottu.bad

sql*loader: release 11.2.0.4.0 - production on mon aug 13 23:10:12 2018

copyright (c) 1982, 2011, oracle and/or its affiliates.  all rights reserved.

commit point reached - logical record count 64
commit point reached - logical record count 128
commit point reached - logical record count 192
commit point reached - logical record count 256
commit point reached - logical record count 320
commit point reached - logical record count 384
commit point reached - logical record count 448
commit point reached - logical record count 512
commit point reached - logical record count 576
commit point reached - logical record count 640
commit point reached - logical record count 704
commit point reached - logical record count 768
commit point reached - logical record count 832
commit point reached - logical record count 896
commit point reached - logical record count 960
commit point reached - logical record count 1000

四.oracle卸载数据-sqludr

　　sqludr是将oracle数据表导出到文本中；是牛人楼方鑫开发的。并非oracle自带工具；需要下载安装才能使用。

4.1 sqludr安装

[oracle@oracle235 ~]$ unzip sqluldr2linux64.zip 
archive:  sqluldr2linux64.zip
  inflating: sqluldr2linux64.bin     
[oracle@oracle235 ~]$ mv sqluldr2linux64.bin $oracle_home/bin/sqludr

4.2 查看sqludr帮助

[oracle@oracle235 ~]$ sqludr -?

sql*unloader: fast oracle text unloader (gzip, parallel), release 4.0.1
(@) copyright lou fangxin (anysql.net) 2004 - 2010, all rights reserved.

license: free for non-commercial useage, else 100 usd per server.

usage: sqluldr2 keyword=value [,keyword=value,...]

valid keywords:
   user    = username/password@tnsname
   sql     = sql file name
   query   = select statement
   field   = separator string between fields
   record  = separator string between records
   rows    = print progress for every given rows (default, 1000000) 
   file    = output file name(default: uldrdata.txt)
   log     = log file name, prefix with + to append mode
   fast    = auto tuning the session level parameters(yes)
   text    = output type (mysql, csv, mysqlins, oracleins, form, search).
   charset = character set name of the target database.
   ncharset= national character set name of the target database.
   parfile = read command option from parameter file 

  for field and record, you can use '0x' to specify hex character code,
  \r=0x0d \n=0x0a |=0x7c ,=0x2c, \t=0x09, :=0x3a, #=0x23, "=0x22 '=0x27

4.3 执行sqludr

[oracle@oracle235 ~]$ sqludr lottu/li0924 query="tbl_load_01" file=lottu01.txt field=","
           0 rows exported at 2018-08-13 23:47:55, size 0 mb.
        1000 rows exported at 2018-08-13 23:47:55, size 0 mb.
         output file lottu01.txt closed at 1000 rows, size 0 mb.

7. Oracle数据加载和卸载