源数据:
-- Create table
create table STU_INFO
(
id NUMBER not null,
name VARCHAR2(8),
score NUMBER(4,1),
class VARCHAR2(2)
)
tablespace STUDENT
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
);
-- Create/Recreate primary, unique and foreign key constraints
alter table STU_INFO
add primary key (ID)
using index
tablespace STUDENT
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
);
CREATE [OR REPLACE] VIEW view_name [(column1, column2, ...)]
AS
SELECT column1, column2, ...
FROM table1, table2, ...
WHERE condition;
CREATE OR REPLACE VIEW STU_INFO_VIEW AS
SELECT STU_INFO.ID,STU_INFO.NAME,STU_INFO.SCORE
FROM STU_INFO WHERE STU_INFO.SCORE>60;
优点: 实时性,简化查询,安全性。 缺点: 影响性能,数据一致性(底层数据发生改变视图数据也会改变)
CREATE [MATERIALIZED] VIEW view_name
[REFRESH {FAST|COMPLETE|FORCE ON | COMMIT | DEMAND}] -- 刷新方式 增量刷新 完全刷新 自动选择|自动刷新 手动刷新 默认: FORCE ON COMMIT
[START WITH date_value]
[NEXT date_value]
[WITH {PRIMARY KEY|ROWID}]
[ENABLE|DISABLE] QUERY REWRITE
AS
select_statement;
CREATE MATERIALIZED VIEW MV_STU_INFO
REFRESH FORCE ON DEMAND
AS
SELECT STU_INFO.ID,STU_INFO.NAME,STU_INFO.SCORE
FROM STU_INFO;
BEGIN
DBMS_MVIEW.REFRESH('MV_STU_INFO', 'C');
END;
-- 执行手动刷新
ps:优点:性能提升,数据一致性,分布式数据处理。 缺点: 占用存储空间,数据更新延迟
-- 前提是必须创建物化视图日志,记录基表发生了哪些变化(增删改查),用这些记录去更新物化视图
CREATE MATERIALIZED VIEW LOG ON "TABLE_NAME" WITH
CREATE MATERIALIZED VIEW LOG ON STU_INFO WITH ID;
CREATE MATERIALIZED VIEW MV_STU_INFO_FAST
REFRESH FAST
AS
SELECT ID,NAME FROM STU_INFO;
SELECT COLUMN_NAME, DATA_TYPE, DATA_LENGTH, NULLABLE
FROM ALL_TAB_COLUMNS
WHERE TABLE_NAME = 'STU_INFO'; -- 替换为实际的表名