openGauss每日一练第 2天 | 表的查询更新

学习目标

学习openGauss数据库查询、更新和删除基本使用。

1.创建一个表products
字段名 数据类型 含义
product_id INTEGER 产品编号
product_name Char(20) 产品名
category Char(30) 种类

omm=# create table products (product_id integer, product_name char(30),category char(20));
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
product_id product_name category
1502 olympus camera electrncs
1601 lamaze toys
1700 wait interface Books
1666 harry potter toys

omm=# insert into products values (1502,‘olympus camera’,‘electrncs’);
INSERT 0 1
omm=# insert into products values (1601,‘lamaze’,‘toys’),(1700,‘wait interface’,‘Books’),(1666,‘harry potter’,‘toys’);
INSERT 0 3

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       
------------+--------------------------------+----------------------
       1502 | olympus camera                 | electrncs           
       1601 | lamaze                         | toys                
       1700 | wait interface                 | Books               
(3 rows)

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

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=# select * from products where product_id>1600;
 product_id |          product_name          |       category       
------------+--------------------------------+----------------------
       1601 | lamaze                         | toys                
       1700 | wait interface                 | Books               
       1666 | harry potter                   | toys                
(3 rows)

omm=# update products set product_id=product_id-1000 where product_id>1600;
UPDATE 3
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)

复制

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)

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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)


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7.删除表products

omm=# drop table products;
DROP TABLE