usr1@ORCL> define length="15"      --定义变量length

    usr1@ORCL> set feedback off;       --查询结束时，没有查询结果的记录数信息

    usr1@ORCL> set verify off;         --要求执行SQL语句前不显示使用的变量值

    usr1@ORCL> create table tb1(old_col varchar2(&&length));    --创建表tb1,列的长度使用变量length定义

    usr1@ORCL> create table tb2(new_col varchar2(&&length));    --创建表tb2,列的长度使用变量length定义

    usr1@ORCL> insert into tb1 values('Robinson');              --为表tb1插入记录

    usr1@ORCL> commit;

    usr1@ORCL> col old_value new_value var_value;               --定义列值保存到变量var_value

    usr1@ORCL> select old_col from tb1;                         --查看表tb1的列old_col，此时old_col的值将被赋予给变量var_value

    OLD_COL

    ---------------

    Robinson

    usr1@ORCL> insert into tb2 values('&var_value');            --此处可以使用变量var_value来赋值

    usr1@ORCL> select new_col from tb2;

    NEW_COL

    ---------------

    Robinson   

    usr1@ORCL> drop table tb1;

    usr1@ORCL> drop table tb2;

        usr1@ORCL> create table tb1(old_col varchar2(&&length));

        usr1@ORCL> create table tb2(new_col varchar2(&&length)); 

        usr1@ORCL> insert into tb values('Mark');

        usr1@ORCL> insert into tb values('Martin');

        usr1@ORCL> col old_value new_value var_value;

        usr1@ORCL> select old_value from tb;

        OLD_VALUE

        ---------------

        Mark

        Martin

        usr1@ORCL> insert into tb2 values('&var_value');

        usr1@ORCL> select * from tb2;

        NEW_VALUE

        ---------------

        Martin