openGauss每日一练第2天 | 查询、更新和删除基本使用

1.创建一个表products

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

一次插入一条:

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');
insert into products (product_id,product_name,category) values (1700,'wait interface','books');
insert into products (product_id,product_name,category) values (1666,'harry potter','toys');

多条记录的方式:

insert into products (product_id,product_name,category) values (1502,'olympus camera','electrncs')
,(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

select * from products limit 1;
product_id | product_name | category
------------+----------------------+--------------------------------
1502 | olympus camera | electrncs
(1 row)

select * from products limit 3;
product_id | product_name | category
------------+----------------------+--------------------------------
1502 | olympus camera | electrncs
1601 | lamaze | toys
1700 | wait interface | books
(3 rows)

 select * from products;

 product_id | product_name | category
------------+----------------------+--------------------------------
1502 | olympus camera | electrncs
1601 | lamaze | toys
1700 | wait interface | books
1666 | harry potter | toys     

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

update products set product_id = product_id -1000 where product_id >1600;
UPDATE 3
select * from products;
product_id | product_name | category
------------+----------------------+--------------------------------
1502 | olympus camera | electrncs
601 | lamaze | toys omm=#
700 | wait interface | books
666 | harry potter | toys    

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

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

delete from products;
select * from products;

7.删除表products

drop table products;