BANNER
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Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE 11.2.0.4.0 Production
TNS for Linux: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production
SQL> create table test(id number(20));
SQL> insert into test values(123456789);
SQL> insert into test values(1234567890);
SQL> insert into test values(12345678901);
SQL> commit;
Commit complete.
SQL> select id from test;
----------
123456789
1234567890
1.2346E+10
SQL> select id from test where id=1234567890;
----------
1234567890
SQL> select id from test where id=12345678901;
----------
1.2346E+10
避免使用科学计数法显示的方法：
1.使用set numwidth
SQL> set numwidth 11
SQL> select id from test where id=12345678901;
-----------
12345678901
2.将number转成char类型
SQL> select to_char(id) from test where id=12345678901;
TO_CHAR(ID)
----------------------------------------
12345678901
Toad和PL/SQL Developer也会存在这样的显示问题，默认情况下这两个工具的numwidth设置都是15，也给我们带来了一些不变，可以通过以下方法：
在toad中->view->option->data->display large number in scientific notation，不选择该选项
在pl/sql developer中->tools->preferences->sql windows->number fields tochar,选中该选项
