调试经验——使用SQLPLUS中的Help功能

问题描述：

最近发现SQLPLUS原来很有用，决定深入学习一下。

首先，SQLPLUS自带帮助文档，使用方式如下。

SQL> help

 HELP
 ----

 Accesses this command line help system. Enter HELP INDEX or ? INDEX
 for a list of topics.

 You can view SQL*Plus resources at
     http://www.oracle.com/technology/documentation/

 HELP|? [topic]

让我们看看到底有哪些topic?

SQL> ? 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

假如我现在对环境变量的设置比较感兴趣，我可以继续查看set命令的用法帮助。

SQL> ? set

 SET
 ---

 Sets a system variable to alter the SQL*Plus environment settings
 for your current session. For example, to:
     -   set the display width for data
     -   customize HTML formatting
     -   enable or disable printing of column headings
     -   set the number of lines per page

 SET system_variable value

 where system_variable and value represent one of the following clauses:

   APPI[NFO]{OFF|ON|text}                   NEWP[AGE] {1|n|NONE}
   ARRAY[SIZE] {15|n}                       NULL text
   AUTO[COMMIT] {OFF|ON|IMM[EDIATE]|n}      NUMF[ORMAT] format
   AUTOP[RINT] {OFF|ON}                     NUM[WIDTH] {10|n}
   AUTORECOVERY {OFF|ON}                    PAGES[IZE] {14|n}
   AUTOT[RACE] {OFF|ON|TRACE[ONLY]}         PAU[SE] {OFF|ON|text}
     [EXP[LAIN]] [STAT[ISTICS]]             RECSEP {WR[APPED]|EA[CH]|OFF}
   BLO[CKTERMINATOR] {.|c|ON|OFF}           RECSEPCHAR {_|c}
   CMDS[EP] {;|c|OFF|ON}                    SERVEROUT[PUT] {ON|OFF}
   COLINVI[SIBLE] {OFF|ON}                    [SIZE {n | UNLIMITED}]
   COLSEP {_|text}                            [FOR[MAT]  {WRA[PPED] |
   CON[CAT] {.|c|ON|OFF}                       WOR[D_WRAPPED] |
   COPYC[OMMIT] {0|n}                          TRU[NCATED]}]
   COPYTYPECHECK {ON|OFF}                   SHIFT[INOUT] {VIS[IBLE] |
   DEF[INE] {&|c|ON|OFF}                      INV[ISIBLE]}
   DESCRIBE [DEPTH {1|n|ALL}]               SHOW[MODE] {OFF|ON}
     [LINENUM {OFF|ON}] [INDENT {OFF|ON}]   SQLBL[ANKLINES] {OFF|ON}
   ECHO {OFF|ON}                            SQLC[ASE] {MIX[ED] |
   EDITF[ILE] file_name[.ext]                 LO[WER] | UP[PER]}
   EMB[EDDED] {OFF|ON}                      SQLCO[NTINUE] {> | text}
   ERRORL[OGGING] {ON|OFF}                  SQLN[UMBER] {ON|OFF}
     [TABLE [schema.]tablename]             SQLPLUSCOMPAT[IBILITY] {x.y[.z]}
     [TRUNCATE] [IDENTIFIER identifier]     SQLPRE[FIX] {#|c}
   ESC[APE] {\|c|OFF|ON}                    SQLP[ROMPT] {SQL>|text}
   ESCCHAR {@|?|%|$|OFF}                    SQLT[ERMINATOR] {;|c|ON|OFF}
   EXITC[OMMIT] {ON|OFF}                    SUF[FIX] {SQL|text}
   FEED[BACK] {6|n|ON|OFF}                  TAB {ON|OFF}
   FLAGGER {OFF|ENTRY|INTERMED[IATE]|FULL}  TERM[OUT] {ON|OFF}
   FLU[SH] {ON|OFF}                         TI[ME] {OFF|ON}
   HEA[DING] {ON|OFF}                       TIMI[NG] {OFF|ON}
   HEADS[EP] {||c|ON|OFF}                   TRIM[OUT] {ON|OFF}
   INSTANCE [instance_path|LOCAL]           TRIMS[POOL] {OFF|ON}
   LIN[ESIZE] {80|n}                        UND[ERLINE] {-|c|ON|OFF}
   LOBOF[FSET] {1|n}                        VER[IFY] {ON|OFF}
   LOGSOURCE [pathname]                     WRA[P] {ON|OFF}
   LONG {80|n}                              XQUERY {BASEURI text|
   LONGC[HUNKSIZE] {80|n}                     ORDERING{UNORDERED|
   MARK[UP] HTML [OFF|ON]                              ORDERED|DEFAULT}|
     [HEAD text] [BODY text] [TABLE text]     NODE{BYVALUE|BYREFERENCE|
     [ENTMAP {ON|OFF}]                             DEFAULT}|
     [SPOOL {OFF|ON}]                         CONTEXT text}
     [PRE[FORMAT] {OFF|ON}]

原来有这么多环境变量可以设置的，自己用过的也就十来个。还需继续努力啊！