Linux下mysq基础命令(二)

1. 创建数据库相关命令:
  mysql> STATUS(\s)  - 列出当前mysql的相关状态信息
  mysql> SHOW DATABASES;  - 显示数据库列表
  mysql> USE DB_name;  - 选中数据库DB_name
  mysql> SHOW TABLES;  - 显示DB_name下的TABLES列表
  mysql> CREATE DATABASE DB_name;  - 创建一个新的数据库,当然,首先你应该以root用户登录,普通用户并没有创建数据库的权利
  mysql> GRANT SELECT,INSERT,DELETE,UPDATE ON DB_name TO user_name IDENTIFIED
      > by 'user_psd';  - 授予新用户user_name对于数据库DB_name的指定权限,登录密码user_psd。该用户拥有的权限:SELECT,INSERT,DELETE,UPDATE
  mysql DB_name -u user_name -p  - 用新创建的用户user_name登录数据库DB_name
  mysql mytest -u root -p  - 用root用户登录数据库DB_name,当我们需要为数据库DB_name创建新表时,需要root用户的权限,如下,创建新表的过程:
  mysql> CREATE TABLE employees (
    - > empid int not null,  - 该字段列值非空
    -> lastname varchar(30),
    -> firstname varchar(30),
    -> salary float,
    -> primary key (empid));  - 该字段列值唯一,"primary key" 表示该列是表的主键, MySQL将自动索引该列
  mysql> SHOW COLUMNS FROM employees;  - 显示employees各字段信息(有时我们需要知道表的结构才能确定插入内容的格式)
  mysql> SHOW CREATE TABLE employees;  - 显示表employees的创建过程,同样可以查看其内部结构
  mysql> INSERT INTO table VALUES (...);  - 向表table插入一条信息,如:mysql> INSERT INTO employees VALUES (1, 'Blum', 'Rich', 25000.00);
    若:mysql> INSERT INTO employees VALUES (1, 'Blum', 'Barbara', 45000.00);
    则:ERROR 1062 (23000): Duplicate entry '1' for key 1
  mysql> DELETE FROM employees WHERE empid = 1;  - 删除empid = 1的那条信息
  mysql> DELETE FROM employees;  - 删除指定数据库表employees的所有项
  mysql> SELECT * FROM employees;  - 查询表employees的所有字段内容,SELECT为查询命令
  mysql> SELECT datafields FROM table;  - 查询字段列表datafields指定的内容(个字段间用“,”分割)。常用的三个过滤器修饰符如下:
    WHERE:显示符合特定条件的数据行子集。如:mysql> SELECT * FROM employees WHERE salary > 40000;
    ORDER BY:以指定顺序显示数据行。
    LIMIT:只显示数据行的一个子集。
  E.G. :
    mysql> SELECT * FROM employees;
    +-------+----------+-----------+--------+
    | empid | lastname | firstname | salary |
    +-------+----------+-----------+--------+
    | 0 | ER | ZHANG | 4500 |
    | 1 | SAN | ZHANG | 5500 |
    | 2 | SI | ZHANG | 6500 |
    | 3 | WU | ZHANG | 7500 |
    | 4 | LIU | ZHANG | 8500 |
    | 5 | QI | ZHANG | 9500 |
    +-------+----------+-----------+--------+
  mysql> SELECT lastname, salary FROM employees WHERE salary > 5000 && salary < 8000;
    +----------+--------+
    | lastname | salary |
    +----------+--------+
    | SAN | 5500 |
    | SI | 6500 |
    | WU | 7500 |
    +----------+--------+
  mysql> SELECT * FROM employees1 ORDER BY lastname (ASC/DECS);  - 按字段lastname排序查询表employees1
  mysql> SELECT * FROM employees1 WHERE salary LIKE '6%';  - 限制salary为数字6开头的项,LIKE字句可以代替“=”使用
  mysql> exit/quit  - 退出数据库软件

2. 新建数据库之后的相关操作:
  ALTER:
    mysql> ALTER TABLE table_name ...;  - 创建表之后,有时我们需要对表的结构进行修改,就用这个作为命令头部
    mysql> ALTER TABLE table_name RENAME (AS) table_new_name;  - 表重命名
    mysql> ALTER TABLE table_name ADD 列名 列数据类型 [AFTER 插入位置];  - 在表中新增一个字段信息
    mysql> ALTER TABLE table_name CHANGE 列名称 列新名称 新数据类型;  - 指定列重命名
    mysql> ALTER TABLE table_name DROP 列名称;  - 删除指定列
  DROP:
    mysql> DROP TABLE table_name;  - 删除指定表
    mysql> DROP DATABASE database_name;  - 删除指定数据库
    mysqladmin -u root -p drop database_name;  - 同样可以使用mysqladmin命令在mysql软件之外删除指定数据库
  UPDATE:
    +-------+----------+-----------+--------+
    | empid | lastname | firstname | salary |
    +-------+----------+-----------+--------+ +-------+----------+-----------+--------+
    | 5 | QI | ZHANG | 9500 |      | 5 | QI | ZHANG | 9500 | 
    | 7 | BA | ZAHNG | 9500 |     -->   | 6 | BA | ZAHNG | 9500 |
    +-------+----------+-----------+--------+ +-------+----------+-----------+--------+
    mysql> UPDATE employees1
      -> SET empid = 6
      -> WHERE lastname = 'BA';  - 限定条件

3. 数据库表间数据复制:http://www.jb51.net/article/47562.htm
  同一数据库表间复制:
    INSERT (INTO) table1 select * from table2;  - 完全复制(mysql测试可用)
    INSERT (INTO) table1 select distinct * from table2;  - 不复制重复纪录(mysql测试不可用)
    INSERT (INTO) table1 select top 5 * from table2;  - 前五条纪录(mysql测试不可用)
  跨数据库表间复制:
    INSERT (INTO) (current.)table1 select * from src_database.table2;  - 完全复制
    INSERT (INTO) (current.)table1 select distinct * from src_database.table2;  - 不复制重复纪录
    INSERT (INTO) (current.)table1 select top 5 * from src_database.table2;  - 前五条纪录
  若table1不存在,则首先应该创建表,并使其结构与src_database结构相同方可copy:
    CREATE TABLE table1 LIKE (src_database.)table2;  - +(src_database.)取决于是否在同一个数据库
    INSERT table1 SELECT * FROM (src_database.)table2;

4. 数据库重命名的几种方法:http://www.cnblogs.com/allenhua/p/5393189.html
  以方法四为例(mysqldump导出数据再导入):mytest -> mytest1
  mysqldump -u root -p mytest > mytest_dump.SQL
  mysql -u root -p -e "CREATE DATABASE mytest1"
  mysql -u root -p mytest1 < mytest_dump.SQL
  mysql -u root -p -e "DROP DATABASE mytest"

5. 数据库用户权限相关:
  mysql> GRANT ALL PRIVILEGES ON mytest1.* TO test@localhost IDENTIFIED BY 'test';  - 授予用户test对于数据库mytest1的所有权限
  mysql> GRANT SELECT, INSERT, DELETE,... ON mytest1.* TO test@localhost IDENTIFIED BY 'test';  - 授予用户test指定权限
  mysql> DELETE FROM user WHERE user = 'test';  - 删除用户test
  mysql> FLUSH PRIVILEGES;  - 刷新各用户权限
  mysql> select * from user;  - 查询所有用户的权利

6. 多表查询:
  mysql> SELECT salary FROM employees1
    -> UNION (ALL)
    -> SELECT salary FROM employees2;  - 合并employees1与employees2两表salary结果,无重复。+(ALL)全列出可重复
      +--------+
      | salary |
      +--------+
      | 4500 |
      | 5500 |
      | 6500 |
      | 7500 |
      | 8500 |
      | 9500 |
      | 10500 |
      | 11500 |
      +--------+
  三种JOIN查询方式:http://www.runoob.com/mysql/mysql-join.html

    两个实例数据库结构如下:
    mysql> SELECT * FROM tcount_tbl;
    +---------------+--------------+
    | runoob_author | runoob_count |
    +---------------+--------------+
    | 菜鸟教程     |   10   |
    | RUNOOB.COM |   20   |
    | Google     |   22   |
    +---------------+--------------+
    mysql> SELECT * from runoob_tbl;
    +-----------+---------------+---------------+-----------------+
    | runoob_id | runoob_title | runoob_author | submission_date |
    +-----------+---------------+---------------+-----------------+
    | 1     | 学习 PHP  | 菜鸟教程   | 2017-04-12 |
    | 2     | 学习 MySQL | 菜鸟教程   | 2017-04-12 |
    | 3     | 学习 Java  | RUNOOB.COM | 2015-05-01 |
    | 4     | 学习 Python | RUNOOB.COM | 2016-03-06 |
    | 5     | 学习 C   | FK        | 2017-04-05 |
    +-----------+---------------+---------------+-----------------+
    INNER JOIN(内连接,或等值连接):获取两个表中字段匹配关系的记录

                
      mysql> SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a 
         -> INNER JOIN tcount_tbl b ON a.runoob_author = b.runoob_author;
      等价于:
      mysql> SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a, tcount_tbl b 
         -> WHERE a.runoob_author = b.runoob_author;
      +-------------+-----------------+----------------+
      | a.runoob_id | a.runoob_author | b.runoob_count |
      +-------------+-----------------+----------------+
    --> | 1 | 菜鸟教程 | 10 |
    --> | 2 | 菜鸟教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      +-------------+-----------------+----------------+
    LEFT JOIN(左连接):获取左表所有记录,即使右表没有对应匹配的记录

                
      mysql> SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a 
         -> LEFT JOIN tcount_tbl b ON a.runoob_author = b.runoob_author;
      +-------------+-----------------+----------------+
      | a.runoob_id | a.runoob_author | b.runoob_count |
      +-------------+-----------------+----------------+
    --> | 1 | 菜鸟教程 | 10 |
    --> | 2 | 菜鸟教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      | 5 | FK | NULL |
      +-------------+-----------------+----------------+
    RIGHT JOIN(右连接):与 LEFT JOIN 相反,用于获取右表所有记录,即使左表没有对应匹配的记录

                
      mysql> SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a 
         -> RIGHT JOIN tcount_tbl b ON a.runoob_author = b.runoob_author;
      +-------------+-----------------+----------------+
      | a.runoob_id | a.runoob_author | b.runoob_count |
      +-------------+-----------------+----------------+
    --> | 1 | 菜鸟教程 | 10 |
    --> | 2 | 菜鸟教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      | NULL | NULL | 22 |
      +-------------+-----------------+----------------+

posted @ 2018-07-23 14:39  Silence&QH  阅读(238)  评论(0编辑  收藏  举报