openGauss数据库创建表、插入记录、查询记录和删除表练习
数据库连接：
root@modb:~# su - omm
omm@modb:~$ gsql -r
创建数据库
omm(# CREATE TABLE customer_t
c_customer_id char(5),
omm(# c_first_name char(6),
omm(# c_last_name char(8)
omm(# ) ;
CREATE TABLE
omm=#
向表中插入一条记录
–列出表中各列字段omm=# INSERT INTO customer_t (c_customer_sk, c_customer_id, c_first_name,c_last_name) VALUES (3769, 5, 'Grace','White');
INSERT 0 1
–如果已经知道表中字段的顺序，也可不列出表中的字段，和上条语法等效
omm=# INSERT INTO customer_t VALUES (3769, 5, 'Grace','White');
INSERT 0 1
向表中插入多条记录
omm=# INSERT INTO customer_t (c_customer_sk, c_customer_id, c_first_name,c_last_name) VALUES
omm-# (6885, 1, 'Joes', 'Hunter'),
omm-# (4321, 2, 'Lily','Carter'),
omm-# (9527, 3, 'James', 'Cook'),
omm-# (9500, 4, 'Lucy', 'Baker');
INSERT 0 4
查看数据
–查看表中记录数omm=# select count(*) from customer_t;
count
-------
6
(1 row)
–查看所有记录
omm=# select * from customer_t;
c_customer_sk | c_customer_id | c_first_name | c_last_name
---------------+---------------+--------------+-------------
3769 | 5 | Grace | White
3769 | 5 | Grace | White
6885 | 1 | Joes | Hunter
4321 | 2 | Lily | Carter
9527 | 3 | James | Cook
9500 | 4 | Lucy | Baker
(6 rows)
–查询表中所有c_first_name记录**
omm=# select c_first_name from customer_t;
c_first_name
--------------
Grace
Grace
Joes
Lily
James
Lucy
(6 rows)
–查询表中所有c_first_name记录，并去掉重复数据
omm=# SELECT DISTINCT(c_first_name) from customer_t;
c_first_name
--------------
James
Grace
Lucy
Joes
Lily
(5 rows)
–查询所有记录，且按c_customer_id升序排列
omm=# select * from customer_t order by c_customer_id;
9500 | 4 | Lucy | Baker
3769 | 5 | Grace | White
3769 | 5 | Grace | White
(6 rows)
omm=# c_customer_sk | c_customer_id | c_first_name | c_last_name
---------------+---------------+--------------+-------------
6885 | 1 | Joes | Hunter
4321 | 2 | Lily | Carter
9527 | 3 | James | Cook
–查询c_first_name为Lily的记录
omm=# select * from customer_t where c_first_name = 'Lily';
c_customer_sk | c_customer_id | c_first_name | c_last_name
---------------+---------------+--------------+-------------
4321 | 2 | Lily | Carter
(1 row)
删除表
drop table customer_t;omm=# drop table customer_t;
DROP TABLE
操作截图：
课后作业练习
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(30) | 产品名 |
| category | Char(20) | 种类 |
omm=# CREATE TABLE products
omm-# (
omm(# product_id INTEGER,
omm(# categoryproduct_name Char(30),
omm(# Char(20)
omm(# );
CREATE TABLE
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 |
插入一条记录:
omm=# insert into products values (1502,'olympus camera','electrncs');
INSERT 0 1
向表中插入多条记录:
omm=# INSERT INTO products values
omm-# (1601,'lamaze','toys'),
omm-# (1700,'wait interface','Books'),
omm-# (1666,'harry potter','toys');
INSERT 0 3
查询表中所有记录及记录数
查询表中所有记录
omm=# select * from products;
1601 | lamaze | toys
1700 | wait interface | Books
1666 | harry potter | toys
(4 rows)
omm=# product_id | product_name | category
------------+--------------------------------+----------------------
1502 | olympus camera | electrncs
查看表中记录数
omm=# select count(*) from products;
count
-------
4
(1 row)
查询表中所有category记录，并将查询结果按升序排序
omm=# SELECT DISTINCT(category) from products;
toys
category
----------------------
electrncs Books
(3 rows)
查询表中category为toys的记录
omm=# select * from products where category = 'toys';
product_id | product_name | category
------------+--------------------------------+----------------------
1601 | lamaze | toys
1666 | harry potter | toys
(2 rows)
删除表products
omm=# drop table products;
DROP TABLE
操作截图：
