openGauss每日一练第18天 | openGauss逻辑结构：视图管理

1.创建表，创建普通视图

--创建模式、表和插入数据
omm=# Create schema tpcds;
CREATE SCHEMA
omm=# omm-# (  c_customer_sk             integer,   
omm(# CREATE TABLE tpcds.customer
  c_customer_id             char(5),    
omm(#   c_first_name              char(6),    
omm(#   c_last_name               char(8) 
omm(# ) ;
CREATE TABLE
omm=# INSERT INTO tpcds.customer VALUES    
omm-# (6885, 1, 'Joes', 'Hunter'),    
omm-# (4321, 2, 'Lily','Carter'),    
omm-# (9527, 3, 'James', 'Cook'),
omm-# (9500, 4, 'Lucy', 'Baker');
INSERT 0 4

--创建视图
omm=# CREATE VIEW tpcds.customer_details_view_v1 AS
WHERE c_customer_sk > 5400;omm-# SELECT * FROM tpcds.customer
omm-# 
CREATE VIEW

--查看视图内容
omm=# select * from tpcds.customer_details_view_v1;
 c_customer_sk | c_customer_id | c_first_name | c_last_name 
---------------+---------------+--------------+-------------
          6885 | 1             | Joes         | Hunter  
          9527 | 3             | James        | Cook    
          9500 | 4             | Lucy         | Baker   
(3 rows)

2.使用视图创建新的视图

omm=# create  VIEW tpcds.part_view as  SELECT * FROM  tpcds.customer_details_view_v1 where  c_customer_sk =9527;
CREATE VIEW

--查看新的视图
omm=# select * from tpcds.part_view;
 c_customer_sk | c_customer_id | c_first_name | c_last_name 
---------------+---------------+--------------+-------------
          9527 | 3             | James        | Cook    
(1 row)

3.创建物化视图

--创建基表
omm=# drop materialized view if exists mv_test;
DROP MATERIALIZED VIEW
omm=# drop table if exists test;
NOTICE:  materialized view "mv_test" does not exist, skipping
omm=# DROP TABLE
create table test(id serial primary key,testnum serial);
NOTICE:  CREATE TABLE will create implicit sequence "test_testnum_seq" for serial column "test.testnum"
NOTICE:  CREATE TABLE will create implicit sequence "test_id_seq" for serial column "test.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE
omm=# insert into test(testnum) values(generate_series(1,100000));
INSERT 0 100000

--创建物化视图：
omm=# create materialized view mv_test as 
omm-# select * from test where testnum%2=0;
omm=# CREATE MATERIALIZED VIEW

--查看物化视图目前有多少行记录：
omm=# select count(*) from mv_test;
 count 
-------
 50000
(1 row)

4.手动更新物化视图

--向基表test插入数据，查看物化视图有多少行记录：
omm=# refresh materialized view mv_test;
REFRESH MATERIALIZED VIEW

--手动更新物化视图，并查看更新物化视图后，物化视图有多少行记录：
omm=# select count(*) from mv_test;
 count  
--------
 100000
(1 row)

5.删除创建的视图

--删除普通视图
omm=# DROP view tpcds.part_view;
DROP VIEW
omm=# DROP view TPCDS.customer_details_view_v1;
DROP VIEW

--删除物化视图
omm=# DROP MATERIALIZED VIEW mv_test;
omm=# DROP MATERIALIZED VIEW