Unix/Linux下可以用man、info查詢命令的具體用法，十分方便，既不需要聯網要求， 也不需要額外開啟所謂的命令大全，對於系統管理員來說，確實是一個不可或缺的好幫手。

在資料庫方面，MySQL、SQLite、MongoDB對SQL、Utility等都提供十分友好的help輸出； Oracle Database也有，但僅有SQL*Plus，SQL的幫助需要額外安裝。

查了下MOS，找到一篇比較古老的文件，最後更新時間是在2003年，那應該是針對Oracle 8i 的，用SQL*Loader匯入。用AvaFind查了下硬碟，發現在我的電腦上還真有8i的help。後來， 也在網路上找了下，走了一些彎路，故寫下備忘，當然也算是一種吐槽。

Oracle’s SQL*Plus Help Facility

Problem Description

You try to use the HELP facility in SQL*Plus and you receive the following error:

'HELP not accessible.'  

Solution Description:

The SQL*Plus HELP facility has not been enabled.

The SQL*Plus HELP facility can be created by performing the following steps:

1. Go to the following directory:

   % cd $ORACLE_HOME/sqlplus/admin/help

2. Login to SQL*Plus as the user SYSTEM.

   % sqlplus system/password

3. Run the “helptbl.sql” script.

   SQL> @helptbl

4. Exit SQL*Plus and execute the following SQL*Loader commands:

   % sqlldr system/manager control=plushelp.ctl

   % sqlldr system/manager control=sqlhelp.ctl

   % sqlldr system/manager control=plshelp.ctl

5. Log back into SQL*Plus as the user SYSTEM and run the “helpindx.sql” script.

   SQL> @helpindx

Solution Explanation:

Performing these steps will build and load the SQL*Plus HELP table.

Install SQL HELP on Oracle 11g

安裝前，僅有SQL*Pus的help（安裝資料庫時一般會自動安裝）：

SQL> help index
help index

Enter Help [topic] for help.

 @             COPY         PAUSE                    SHUTDOWN
 @@            DEFINE       PRINT                    SPOOL
 /             DEL          PROMPT                   SQLPLUS
 ACCEPT        DESCRIBE     QUIT                     START
 APPEND        DISCONNECT   RECOVER                  STARTUP
 ARCHIVE LOG   EDIT         REMARK                   STORE
 ATTRIBUTE     EXECUTE      REPFOOTER                TIMING
 BREAK         EXIT         REPHEADER                TTITLE
 BTITLE        GET          RESERVED WORDS (SQL)     UNDEFINE	
 CHANGE        HELP         RESERVED WORDS (PL/SQL)  VARIABLE	
 CLEAR         HOST         RUN                      WHENEVER OSERROR	
 COLUMN        INPUT        SAVE                     WHENEVER SQLERROR	
 COMPUTE       LIST         SET                      XQUERY	
 CONNECT       PASSWORD     SHOW


SQL> help topics
help topics
Help is available on the following topics:
/
@
@@
ACCEPT
APPEND
ARCHIVE LOG
ATTRIBUTE
BREAK
BTITLE
CHANGE
... ...
XQUERY

HELP表system.help結構：

SQL> desc system.help
desc system.help

 Name			  Null?     Type	
 ---------------- --------- ------------------
 TOPIC		      NOT NULL  VARCHAR2(50)
 SEQ			  NOT NULL  NUMBER
 INFO					    VARCHAR2(80)

檢視當前Help數：

select count(1) from system.help;
  COUNT(*)
----------
       919

help create相關主題：

SQL> help create
SP2-0172: No HELP matching this topic was found.

SQL*Plus幫助檔案路徑：

[[email protected] ~]$ cd /db/oracle/product/11.2.0/db_1/sqlplus/admin/help/
[[email protected] help]$ ll
total 80
-rw-r--r--. 1 oracle oinstall   265 Feb 17  2003 helpbld.sql
-rw-r--r--. 1 oracle oinstall   337 Jun 28  2000 helpdrop.sql
-rw-r--r--. 1 oracle oinstall 65975 Jun 29  2009 helpus.sql
-rw-r--r--. 1 oracle oinstall  2086 Jan  6  2009 hlpbld.sql

以上指令碼簡介：

• helpbld.sql：Invoke and execute the script to loads the SQL*Plus HELP system and upon completion, exit the SQL*Plus connection. Code: @@&1/hlpbld.sql &2
• helpdrop.sql：Drops the SQL*Plus HELP table
• helpus.sql：Inserts SQL*Plus HELP text in English. This script is called from helpbld.sql
• hlpbld.sql：Builds the SQL*Plus HELP table and loads the HELP data from a data file. The data file must exist before this script is run.

在安裝Oracle資料庫時預設已經安裝一些Help，不過主要是針對SQL*Plus，對Oracle SQL 的Help沒有。查MOS，暫且僅找到8i自帶的SQL Help。在CSDN上找了下，有一個help.sql腳 本，針對SQL語法的，對DBA日常管理應該已經夠用。下載連結見文末參考。

上傳help.sql檔案：

[[email protected] help]$ rz
rz waiting to receive.**B0100000023be50
?

[[email protected] help]$ ll
total 596
-rw-r--r--. 1 oracle oinstall    265 Feb 17  2003 helpbld.sql
-rw-r--r--. 1 oracle oinstall    337 Jun 28  2000 helpdrop.sql
-rw-r--r--. 1 oracle oinstall 527523 May 11  2005 help.sql
-rw-r--r--. 1 oracle oinstall  65975 Jun 29  2009 helpus.sql
-rw-r--r--. 1 oracle oinstall   2086 Jan  6  2009 hlpbld.sql

安裝help.sql：

[[email protected] help]$ pwd
/db/oracle/product/11.2.0/db_1/sqlplus/admin/help
[[email protected] help]$ sqlplus system/oracle

SQL*Plus: Release 11.2.0.1.0 Production on Tue Jan 22 17:15:58 2013

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> @helpbld
Enter value for 1: /db/oracle/product/11.2.0/db_1/sqlplus/admin/help
Enter value for 2: /db/oracle/product/11.2.0/db_1/sqlplus/admin/help/help.sql

PL/SQL procedure successfully completed.

安裝後，檢視help：

[email protected] help]$ sqlplus  /nolog

SQL*Plus: Release 11.2.0.1.0 Production on Tue Jan 22 17:17:54 2013

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

SQL> conn /as sysdba
Connected.
SQL> select count(1) from system.help;

  COUNT(1)
----------
      5085

SQL> help index
 Use the HELP TOPIC command for a list of help topics.

SQL> help topic
 Help is available on the following topics:

%ROWTYPE ATTRIBUTE
%TYPE ATTRIBUTE
/
@
@@
ACCEPT
ALLOCATE (EMBEDDED SQL)
ALTER CLUSTER
ALTER DATABASE
ALTER FUNCTION
ALTER INDEX
ALTER PACKAGE
ALTER PROCEDURE
ALTER PROFILE
ALTER RESOURCE COST
ALTER ROLE
ALTER ROLLBACK SEGMENT
ALTER SEQUENCE
ALTER SESSION
... ...

help create database示例：

SQL> help create database

 CREATE DATABASE
 ---------------

 Use this command to create a database, making it available for
 general use, with the following options:

   *  to establish a maximum number of instances, data files, redo
      log files groups, or redo log file members
   *  to specify names and sizes of data files and redo log files
   *  to choose a mode of use for the redo log
   *  to specify the national and database character sets

 Warning: This command prepares a database for initial use and erases
 any data currently in the specified files. Only use this command
 when you understand its ramifications.

 CREATE DATABASE [database]
   { CONTROLFILE REUSE
   | LOGFILE [GROUP integer] filespec
           [,[GROUP integer] filespec] ...
   | MAXLOGFILES integer
   | MAXLOGMEMBERS integer
   | MAXLOGHISTORY integer
   | MAXDATAFILES integer
   | MAXINSTANCES integer
   | {ARCHIVELOG | NOARCHIVELOG}
   | EXCLUSIVE
   | CHARACTER SET charset
   | NATIONAL CHARACTER SET charset
   | DATAFILE filespec [AUTOEXTEND {OFF | ON [NEXT integer [K | M] ]
                       [MAXSIZE { UNLIMITED | integer [K | M]} ] } ]
           [, filespec [AUTOEXTEND {OFF | ON [NEXT integer [K | M] ]
                       [MAXSIZE { UNLIMITED | integer [K | M]} ] } ] ] ...} ...

 For detailed information on this command, see the Oracle8 Server SQL
 Reference.


 CREATE DATABASE LINK
 --------------------

 Use this command to create a database link. A database link is a
 schema object in the local database that allows you to access
 objects on a remote database or to mount a secondary database in
 read-only mode. The remote database can be either an Oracle or a
 non-Oracle system.

 CREATE [PUBLIC] DATABASE LINK dblink
   [CONNECT TO user IDENTIFIED BY password]
   [USING 'connect_string']

 For detailed information on this command, see the Oracle8 Server SQL
 Reference.

Reference