openGauss每日一练第一天

openGauss每日一练第一天

学习地址

https://www.modb.pro/course/133

学习目标

​ 学习openGauss数据库创建表、插入记录、查询记录和删除表基本使用。

课后作业

1.创建一个表products

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

omm=# create table products
omm-# (product_id integer,
omm(#  product_name char(30),
omm(#  category char(20)
omm(# );
CREATE TABLE
omm=# 
omm=# \dt+ products
                                       List of relations
 Schema  |   Name   | Type  | Owner |  Size   |             Storage              | Description 
---------+----------+-------+-------+---------+----------------------------------+-------------
 schema2 | products | table | omm   | 0 bytes | {orientation=row,compression=no} | 
(1 row)

omm=# 
omm=# \d+ products
                             Table "schema2.products"
    Column    |     Type      | Modifiers | Storage  | Stats target | Description 
--------------+---------------+-----------+----------+--------------+-------------
 product_id   | integer       |           | plain    |              | 
 product_name | character(30) |           | extended |              | 
 category     | character(20) |           | extended |              | 
Has OIDs: no
Options: orientation=row, compression=no

omm=# 

2.向表中插入数据，采用一次插入一条和多条记录的方式

SQL文本：
insert into products(product_id,product_name,category) values (1502,'olympus camera','electrncs');
insert into products values (1601,'lamaze','toys');
insert into products(product_id,product_name,category) values 
(1700,'wait interface','Books'),
(1666,'harry potter','toys');

omm=# insert into products(product_id,product_name,category) values (1502,'olympus camera','electrncs');
INSERT 0 1
omm=# insert into products values (1601,'lamaze','toys');
INSERT 0 1
omm=# insert into products(product_id,product_name,category) values 
omm-# (1700,'wait interface','Books'),
omm-# (1666,'harry potter','toys');
INSERT 0 2
omm=# 

3.查询表中所有记录及记录数

SQL文本：
查询表中所有记录：
select * from products;

查询表中记录数：
select count(*) from products;

查询表中所有记录：
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)
omm=# 

查询表中记录数：
omm=# select count(*) from products;
 count 
-------
     4
(1 row)

omm=# 

4.查询表中所有category记录，并将查询结果按升序排序

SQL文本：
select category from products order by category; --利用order by进行升序排序

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

omm=# 

5.查询表中category为toys的记录

SQL文本：
select * from products where category='toys';  --利用where进行条件筛选

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

omm=# 

6.删除表products

SQL文本：
drop table products;

omm=# drop table products;
DROP TABLE
omm=#