半天搞定MySQL（全）
半天搞定MySQL（全）一
半天搞定MySQL（全）二
半天搞定MySQL（全）三
半天搞定MySQL（全）四
半天搞定MySQL（全）六
博主用的是8.0版本的MySQL，储存引擎是InnoDB，关于InnoDB这里不详细解释，需要的话推荐了解这篇博文（或者自行百度）https://www.jianshu.com/p/519fd7747137
10. 复制表
***复制表city_spots:
步骤一：
获取数据表的结构：
mysql> SHOW CREATE TABLE city_spots;
| Table | Create Table |
| city_spots | CREATE TABLE `city_spots` (
`city_name` varchar(20) NOT NULL,
`place_of_interest'` varchar(20) DEFAULT NULL,
`city_score` int DEFAULT NULL,
`cost_rmb` float DEFAULT NULL,
`time_way` float DEFAULT NULL,
`time_stay` float DEFAULT NULL,
PRIMARY KEY (`city_name`),
KEY `city` (`city_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
步骤二：
修改新数据表名，并附上表结构：
mysql> CREATE TABLE `clone_city_spots` (
-> `city_name` varchar(20) NOT NULL,
-> `place_of_interest'` varchar(20) DEFAULT NULL,
-> `city_score` int DEFAULT NULL,
-> `cost_rmb` float DEFAULT NULL,
-> `time_way` float DEFAULT NULL,
-> `time_stay` float DEFAULT NULL,
-> PRIMARY KEY (`city_name`),
-> KEY `city` (`city_name`)
-> ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
-> ;
Query OK, 0 rows affected (0.04 sec)
步骤三：
拷贝数据
全部复制：
mysql> insert into clone_city_spots
-> select * from city_spots;
Query OK, 11 rows affected (0.01 sec)
Records: 11 Duplicates: 0 Warnings: 0
或者部分复制：
mysql> insert into clone2_city_spots(city_name,city_score,cost_rmb)
-> select city_name,city_score,cost_rmb from city_spots;
Query OK, 11 rows affected (0.01 sec)
Records: 11 Duplicates: 0 Warnings: 0
mysql> select * from clone2_city_spots;
+-----------+--------------------+------------+----------+----------+-----------+
| city_name | place_of_interest' | city_score | cost_rmb | time_way | time_stay |
+-----------+--------------------+------------+----------+----------+-----------+
| America | NULL | 82 | 20000 | NULL | NULL |
| Iceland | NULL | 88 | 19000 | NULL | NULL |
| Italy | NULL | 79 | 20000 | NULL | NULL |
| Janpan | NULL | 85 | 15000 | NULL | NULL |
| 上海 | NULL | 80 | 13000 | NULL | NULL |
| 东北 | NULL | 86 | 10000 | NULL | NULL |
| 北京 | NULL | 93 | 15000 | NULL | NULL |
| 新疆 | NULL | 90 | 12000 | NULL | NULL |
| 海南 | NULL | 78 | 9000 | NULL | NULL |
| 西安 | NULL | 83 | 5500 | NULL | NULL |
| 香港 | NULL | 76 | 8000 | NULL | NULL |
+-----------+--------------------+------------+----------+----------+-----------+
11 rows in set (0.00 sec)
或者（把步骤二和步骤三合在一起，省略步骤二）
一步到位，直接复制表：
复制旧表的部分内容形成新表
mysql> create table clone2_city_spots as(
-> select city_name,city_score,cost_rmb from city_spots);
Query OK, 11 rows affected (0.03 sec)
Records: 11 Duplicates: 0 Warnings: 0
结果：
mysql> select * from clone2_city_spots;
+-----------+------------+----------+
| city_name | city_score | cost_rmb |
+-----------+------------+----------+
| America | 82 | 20000 |
| Iceland | 88 | 19000 |
| Italy | 79 | 20000 |
| Janpan | 85 | 15000 |
| 上海 | 80 | 13000 |
| 东北 | 86 | 10000 |
| 北京 | 93 | 15000 |
| 新疆 | 90 | 12000 |
| 海南 | 78 | 9000 |
| 西安 | 83 | 5500 |
| 香港 | 76 | 8000 |
+-----------+------------+----------+
11 rows in set (0.01 sec)
或者 复制整个旧表，形成新表
mysql> create table clone2_city_spots as(
-> select * from city_spots);
Query OK, 11 rows affected (0.03 sec)
Records: 11 Duplicates: 0 Warnings: 0
结果：
mysql> select * from clone2_city_spots;
+-----------+--------------------+------------+----------+----------+-----------+
| city_name | place_of_interest' | city_score | cost_rmb | time_way | time_stay |
+-----------+--------------------+------------+----------+----------+-----------+
| America | 未知 | 82 | 20000 | 1.5 | 4 |
| Iceland | Ice | 88 | 19000 | 1.5 | 5 |
| Italy | food | 79 | 20000 | 1 | 4 |
| Janpan | 未知 | 85 | 15000 | 1 | 3 |
| 上海 | 购物 | 80 | 13000 | 1 | 2.5 |
| 东北 | 雪 | 86 | 10000 | 1.5 | 5 |
| 北京 | 长城 | 93 | 15000 | 1 | 3 |
| 新疆 | 水果 | 90 | 12000 | 1.5 | 5 |
| 海南 | 沙滩 | 78 | 9000 | 1 | 4 |
| 西安 | 兵马俑 | 83 | 5500 | 1 | 3 |
| 香港 | 未知 | 76 | 8000 | 1 | 3 |
+-----------+--------------------+------------+----------+----------+-----------+
11 rows in set (0.00 sec)
11. 元数据
除了表数据以外的数据都是元数据，也被叫做基表。比如库/表属性，列名、数据库名、用户名、版本名，状态信息，权限等。
获取元数据
- show
查看数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| citys |
| class |
| information_schema |
| mysql |
| performance_schema |
| sakila |
| sys |
| world |
+--------------------+
8 rows in set (0.00 sec)
查看citys里的数据表
mysql> show tables;
+-------------------+
| Tables_in_citys |
+-------------------+
| c_f |
| city_journey |
| city_play |
| city_spots |
| clone2_city_spots |
| clone_city_spots |
| runoob_tbl |
+-------------------+
7 rows in set (0.00 sec)
- select
本数据库查看一个表格的数据
mysql> select * from city_play;
+-----------+------------+-------+------------+-------------+---------+
| city_name | city_thing | cost | journey_ID | thing_score | play_ID |
+-----------+------------+-------+------------+-------------+---------+
| 海南 | 潜水 | 15000 | 1 | 95 | 1 |
| 夏威夷 | 水 | NULL | 2 | 88 | 2 |
| 香港 | 潜水 | NULL | 10 | 95 | 10 |
| Janpan | woman | NULL | 11 | 90 | 11 |
+-----------+------------+-------+------------+-------------+---------+
4 rows in set (0.01 sec)
跨数据库查看一个表格的数据
mysql> select user,password_expired,host,Password_reuse_history from mysql.user;
+------------------+------------------+-----------+------------------------+
| user | password_expired | host | Password_reuse_history |
+------------------+------------------+-----------+------------------------+
| Amos | N | % | NULL |
| laowang | N | localhost | NULL |
| mo | N | localhost | NULL |
| mysql.infoschema | N | localhost | NULL |
| mysql.session | N | localhost | NULL |
| mysql.sys | N | localhost | NULL |
| root | N | localhost | NULL |
| user | N | localhost | NULL |
+------------------+------------------+-----------+------------------------+
8 rows in set (0.00 sec)
- MySQL命令
查看当前服务器版本信息
mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.20 |
+-----------+
1 row in set (0.00 sec)
查看当前数据库
mysql> select database();
+------------+
| database() |
+------------+
| citys |
+------------+
1 row in set (0.00 sec)
查看当前用户
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
服务器状态
mysql> show status;
服务器配置变量
mysql> show variables;
查看具体某个表具体信息
mysql> desc c_f;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| people | varchar(20) | YES | UNI | NULL | |
| city_name | varchar(20) | NO | | NULL | |
| city_food | varchar(20) | YES | | NULL | |
| p | int | NO | | 0 | |
| food_kinds | int | YES | | NULL | |
| food_ID | int | NO | MUL | NULL | |
+------------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)
未完待续。。。。。
半天搞定MySQL（全）一
半天搞定MySQL（全）二
半天搞定MySQL（全）三
半天搞定MySQL（全）四
半天搞定MySQL（全）六