PL/SQL常用函数（日期、字符、数字、转换、其他、分组）
--create table test as select * from T1 where 1=2; --复制表结构，不复制数据--select * from test;--create table test2 as select * from T1;--复制整个表到test2--select * from test2;--insert into test select * from T1;--将
--create table test as select * from T1 where 1=2; --复制表结构，不复制数据--select * from test;--create table test2 as select * from T1;--复制整个表到test2--select * from test2;--insert into test select * from T1;--将