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

omm=# CREATE TABLE products
omm-#( product_id integer,
product_name char(30),
omm(# category char(20)
omm(# ) ;
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
omm-# (1601, 'lamaze', 'toys'),
omm-# (1700, 'wait interface', 'Books'),
omm-# (1666, 'harry potter','toys');
INSERT 0 3
omm=#

3.获取表中一条记录、三条记录和所有记录

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

omm=#
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
------------+--------------------------------+----------------------
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
omm=#