有些时候在使用sql*plus时忘记了一些命令的用法，其实我们大可不必到什么地方去查，，我们只需要在sql*plus中查看就可以了，
使用help | ？ parameter
例如在sql*plus中：
SQL> help columnCOLUMN——Specifies display attributes for a given column, such as: – text for the column heading – alignment for the column heading – format for NUMBER data – wrapping of column dataAlso lists the current display attributes for a single columnor all columns.
COL[UMN] [{column | expr} [option …] ]
where option represents one of the following clauses: ALI[AS] alias CLE[AR] ENTMAP {ON|OFF} FOLD_A[FTER] FOLD_B[EFORE] FOR[MAT] format HEA[DING] text JUS[TIFY] {L[EFT] | C[ENTER] | R[IGHT]} LIKE {expr | alias} NEWL[INE] NEW_V[ALUE] variable NOPRI[NT] | PRI[NT] NUL[L] text OLD_V[ALUE] variable ON|OFF WRA[PPED] | WOR[D_WRAPPED] | TRU[NCATED]
也可以使用？，如下：
SQL> ? showSHOW—-Shows the value of a SQL*Plus system variable, or the currentSQL*Plus environment. SHOW SGA requires a DBA privileged login.SHO[W] optionwhere option represents one of the following terms or clauses: system_variable ALL BTI[TLE] CON_ID CON_NAME ERR[ORS] [{FUNCTION | PROCEDURE | PACKAGE | PACKAGE BODY | TRIGGER | VIEW | TYPE | TYPE BODY | DIMENSION | JAVA CLASS} [schema.]name] LNO PARAMETERS [parameter_name] PDBS PNO RECYC[LEBIN] [original_name] REL[EASE] REPF[OOTER] REPH[EADER] SGA SPOO[L] SPPARAMETERS [parameter_name] SQLCODE TTI[TLE] USER
红色的语句就是该命令的sql语句，然后下面就是对它的一些参数的说明。
功夫不负有心人。
