openGauss每日一练第18天

学习内容：视图的管理

1.使用gsql -r登录opengauss数据库

root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

2.创建一个schema并在该schema下创建一个表。插入部分数据

omm=# create schema tpcds;
CREATE SCHEMA
omm=# \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 tpcds           | omm
(11 rows)

omm=# CREATE TABLE tpcds.customer                   
omm-# (  c_customer_sk             integer,   
omm(# omm(#   c_customer_id             char(5),    
  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
omm=# 
omm=# select * from tpcds.customer;
 c_customer_sk | c_customer_id | c_first_name | c_last_name 
---------------+---------------+--------------+-------------
          6885 | 1             | Joes         | Hunter  
          4321 | 2             | Lily         | Carter  
          9527 | 3             | James        | Cook    
          9500 | 4             | Lucy         | Baker   
(4 rows)

3.在该表的基础上创建视图并查看视图内容

omm=# create view tpcds.view1 as select * from tpcds.customer where c_first_name like 'L%';
CREATE VIEW

omm=# select * from tpcds.view1;
 c_customer_sk | c_customer_id | c_first_name | c_last_name 
---------------+---------------+--------------+-------------
          4321 | 2             | Lily         | Carter  
          9500 | 4             | Lucy         | Baker   
(2 rows)

4.在视图的基础上创建视图并查看其内容

omm=# create view tpcds.view2 as select * from tpcds.view1 where c_customer_sk>5000;
CREATE VIEW
omm=# select * from tpcds.view2;
 c_customer_sk | c_customer_id | c_first_name | c_last_name 
---------------+---------------+--------------+-------------
          9500 | 4             | Lucy         | Baker   
(1 row)

5.创建一个表。生成一些数据

omm=# create table test(id serial primary key,testnum serial);
NOTICE:  CREATE TABLE will create implicit sequence "test_id_seq" for serial column "test.id"
NOTICE:  CREATE TABLE will create implicit sequence "test_testnum_seq" for serial column "test.testnum"
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

6.在刚才创建的表的基础上创建一个物化视图并查看其数据量。

omm=# create materialized view mv_test as select * from test where testnum>80000;
CREATE MATERIALIZED VIEW

omm=# select count(*) from mv_test;
 count 
-------
 20000
(1 row)

7.查看物化视图相关系统表

omm=# select * from GS_MATVIEW;
 matviewid | mapid | ivm | needrefresh | refreshtime 
-----------+-------+-----+-------------+-------------
     16412 |     0 | f   |             | 
(1 row)

8.利用refresh materialized命令手动更新物化视图

omm=# insert into test(testnum) values(generate_series(1,100000));
INSERT 0 100000
omm=# select count(*) from mv_test;
omm=#  count 
-------
 20000
(1 row)
omm=# refresh materialized view mv_test;
REFRESH MATERIALIZED VIEW
omm=# select count(*) from mv_test;
(1 row)

omm=#  count 
-------
 40000

9.删除视图。

omm=# drop view tpcds.view2;
DROP VIEW
omm=# drop view tpcds.view1;
DROP VIEW
omm=# drop materialized view mv_test;
DROP MATERIALIZED VIEW