17.08.02

instead of trigger视图触发器

 

replace

 

序列:

SQL> create sequence test_seq increment by 1 start with 1 maxvalue 1000 nocycle cache 20;

SQL> create table t1(x int primary key, y int);

SQL> insert into t1 values (test_seq.nextval, 11);           反复执行

SQL> select * from t1;

 

索引:

主键和唯一性约束自动创建索引:

SQL> select constraint_name, constraint_type from user_constraints where table_name='EMPLOYEES';

SQL> select index_name, index_type from user_indexes where table_name='EMPLOYEES';

SQL> set autot on

SQL> select last_name from employees where employee_id=100;      走索引

SQL> select email from employees;                                                            走索引

SQL> select last_name from employees where salary=2100;                 全表扫描

SQL> create index emp_salary_ix on employees(salary);

SQL> select last_name from employees where salary=2100;                 走索引

SQL> set autot off

 

User process:用户进程

Server process:服务器进程

Shared pool:共享池

Library cache:库高速缓存

Data dict cache:数据字典高速缓存

Database buffer cache:数据库缓冲区高速缓存

Redo log buffer cache:重做日志缓冲区

Parameter file:参数文件

Password file:口令文件

Data files:数据文件

Control files:控制文件

Redo log buffer cache:重做日志文件

Archived log files:归档日志文件

视图:保持数据的独立性

视图不允许做dml操作

posted on 2017-08-19 08:49  zhang_x  阅读(79)  评论(0编辑  收藏  举报

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