openGauss每日一练第2天 | 学习心得体会【少安】

课程标题

2.1 openGauss查询、更新和删除基本使用

学习目标

学习openGauss数据库查询、更新和删除基本使用。

课程学习

连接openGauss

#第一次进入等待15秒 
#数据库启动中... 
su - omm 
gsql -r

1.创建数据表

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

2.向表中插入记录

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

3.查看数据
–获取表中全部记录
select * from customer_t;
–获取表中两条记录
select * from customer_t limit 2;
–查询表中所有c_first_name的字段，并以别名c_name输出
select c_first_name as c_name from customer_t;

4.更新数据–更新所有记录
update customer_t set c_customer_id = c_customer_id + 100;
–查看数据
select * from customer_t;
–更新c_customer_sk*2 < 5000的记录
update customer_t set c_customer_sk = c_customer_sk * 2 where c_customer_sk < 5000;
–查看数据
select * from customer_t;5.删除数据
–删除c_first_name为Lucy的记录
delete from customer_t where c_first_name = ‘Lucy’;
–查看数据
select * from customer_t;
–删除所有数据
delete from customer_t;
–查看数据
select * from customer_t;6.删除表
drop table customer_t;

课后作业

1.创建一个表products

-- 1.
CREATE TABLE products
( product_id integer ,
product_name char(20),
category char(30)
) ;

2.向表中插入数据，采用一次插入一条和多条记录的方式

-- 2.
INSERT INTO products (product_id, product_name, category) VALUES (1502, 'olympus camera', 'electrncs');

INSERT INTO products (product_id, product_name, category) VALUES
(1601, 'lamaze', 'toys'),
(1700, 'wait interface', 'Books'),
(1666, 'harry potter', 'toys')
;

3.获取表中一条记录、三条记录和所有记录

-- 3.
select * from products limit 1;
select * from products limit 3;
select * from products;

4.将满足product_id > 1600的记录的product_id更新为product_id – 1000，并查看products中所有记录是否更新成功

-- 4.
select * from products;
update products 
 set product_id = product_id - 1000 
 where product_id > 1600
;
select * from products;

5.删除category为toys的所有记录，并查看products中数据是否删除成功

-- 5.
select * from products;
delete from products
 where category = 'toys'
;
select * from products;

6.删除products中所有数据，并查看数据是否删除成功

-- 6.
delete from products;
select * from products;

7.删除表products

-- 7.
drop table products;

学习心得

本节的课后习题，表products的字段定义与上一节的有略微差异，各位同学注意到了么？😃

参考文档

openGauss每日一练 | by 少安 | 汇总

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