摘要:
DDL(date definition language)数据库定义语言 create scott@TEST>create table t1 ( id number(8), name varchar2(5), sex char(1),year date ); //创建一个新表 scott@TEST> 阅读全文
摘要:
1.select ename as "aa",sal from emp; //用as关键字,别名用双引 2.select distinct sal from emp; //distinct 去掉重复的行 3.select ename,sal,deptno from emp order by 3 de 阅读全文
摘要:
select 1 from table ;select any col from table (any col is any row of purpose collection) ;select * from table 作用上来说是没有差别的,都是查看是否有数据记录,一般是做条件用的。Select 阅读全文