1、创建database link

create database link oracle_test_link connect to oracle_test identified by zhouxufeng using 'orcl';

?2、创建同义词

create synonym emp_syn for emp@oracle_test_link;
create synonym logs_syn for logs@oracle_test_link;

?3、创建表

create table emp as select * from emp_syn;
create table logs as select * from logs_syn;
create table dep(
       dep_id number primary key,
       dep_name varchar2(50) not null,
       dep_address varchar2(50)
)

?4、Oracle中的DDL语句

--在表中增加一列
alter table emp add(emp_dep_id number); 
--更改列的类型
alter table emp modify(emp_name varchar(200));
--更改列的名称
alter table emp rename column emp_name1 to emp_name;

?5、创建序列

create sequence emp_seq increment by 1 start with 1 maxvalue 9999 nocycle cache 10
create sequence logs_seq increment by 1 start with 1 maxvalue 9999 nocycle cache 10

?6、使用distinct来过滤重复数据

select distinct e.emp_name from emp e

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