openGauss每日一练第2天 数据库查询、更新、删除基本使用

1.创建一个表products

root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 2.0.0 build 78689da9) compiled at 2021-03-31 21:03:52 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# create table products
omm-# (product_id integer,
omm(# product_name char(20),
omm(# category char(30));
CREATE TABLE

2.向表中插入数据，采用一次插入一条和多条记录的方式

omm=# insert into products values(1502,'olympus camera','electrncs');
INSERT 0 1
omm=# insert into products values(1601,'lamaze','toys');
INSERT 0 1
omm=# insert into products values(1700,'wait interface','Books');
INSERT 0 1
omm=# insert into products values(1666,'harry potter','toys');
INSERT 0 1

3.获取表中一条记录、三条记录和所有记录

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

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


omm=# select * from products;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1502 | olympus camera       | electrncs                     
       1601 | lamaze               | toys                          
       1700 | wait interface       | Books                         
       1666 | harry potter         | toys                          
(4 rows)

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

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

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

omm=# delete from products where category='toys';
DELETE 2
omm=# select * from products;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1502 | olympus camera       | electrncs                     
        700 | wait interface       | Books                         
(2 rows)

6.删除products中所有数据，并查看数据是否删除成功

omm=# delete from products;
DELETE 2
omm=# select * from products;
 product_id | product_name | category 
------------+--------------+----------
(0 rows)

7.删除表products

omm=# drop table products;
DROP TABLE