openGauss每日一练第1天 | 学习心得体会

1. 墨天轮实验环境初探：

实训环境是虚拟机 + 文字， 这种方式学习很好，比视频更容易沉浸。

2. 摩天轮文章写作：

采用markdown形式很容易排版，整体网站非常不错。

3. 实验内容

1. 切换用户 omm
2. 连接数据库 gsql直接连上5432端口

# -r if this parameter is set,use libedit
gsql - r

3. 开始创建表

CREATE TABLE customer_t
(  c_customer_sk             integer,   
  c_customer_id             char(5),    
  c_first_name              char(6),    
  c_last_name               char(8) 
) ;

INSERT INTO customer_t (c_customer_sk, c_customer_id, c_first_name,c_last_name) VALUES (3769, 5, 'Grace','White');

INSERT INTO customer_t VALUES (3769, 5, 'Grace','White');

INSERT INTO customer_t (c_customer_sk, c_customer_id, c_first_name,c_last_name) VALUES    
(6885, 1, 'Joes', 'Hunter'),    
(4321, 2, 'Lily','Carter'),    
(9527, 3, 'James', 'Cook'),
(9500, 4, 'Lucy', 'Baker');

在实验中有时候会出现吞字符的情况，在文档的时候就把代码写出来我觉得是一个比较好的选择

4. 查询

omm=# select * from customer_t;
 c_customer_sk | c_customer_id | c_first_name | c_last_nam
e 
---------------+---------------+--------------+-----------
--
          3769 | 5             | Grace        | White   
          3769 | 5             | Grace        | White   
          6885 | 1             | Joes         | Hunter  
          4321 | 2             | Lily         | Carter  
          9527 | 3             | James        | Cook    
          9500 | 4             | Lucy         | Baker   
(6 rows)

因为没有设置主键，所以有重复记录。

omm=# select c_first_name, count(*) count from customer_t group by c_first_name;
 c_first_name | count 
--------------+-------
 James        |     1
 Grace        |     2
 Lucy         |     1
 Joes         |     1
 Lily         |     1
(5 rows)

4. 课后作业

create table products
(product_id integer,
product_name char(30),
category char(20)
);

insert into products values (1520, 'olympus camera' , 'electrncs');

insert into products values
(1601, 'lamaze', 'toys'),
(1700, 'wait interface', 'Books'),
(1666, 'harry potter', 'toys');

select * from products;
select count(*) from products;
select category from products order by category ASC;
select * from products where category='toys';
drop table products;

5. 结果

omm=# select * from products;
 product_id |          product_name          |       categ
ory       
------------+--------------------------------+------------
----------
       1520 | olympus camera                 | electrncs  
         
       1601 | lamaze                         | toys       
         
       1700 | wait interface                 | Books      
         
       1666 | harry potter                   | toys       
         
(4 rows)

omm=# select count(*) from products;
 count 
-------
     4
(1 row)

omm=# select category from products order by category ASC;
       category       
----------------------
 Books               
 electrncs           
 toys                
 toys                
(4 rows)

omm=# select * from products where category='toys';
 product_id |          product_name          |       categ
ory       
------------+--------------------------------+------------
----------
       1601 | lamaze                         | toys       
         
       1666 | harry potter                   | toys       
         
(2 rows)

完成课时1~