Linux下MySQL 數據庫的基本操作


1. 創建數據庫相關命令:
  首先,下載MySQL相關軟件包:aptitude install mysql-server/mysql-client
  MySQL中的root用戶類似於Linux下的root用戶,擁有最多高的權限,若操作不當會對數據造成嚴重的危害。因此,針對每一個應用程序創建對應的數據庫及操作用戶是一個好習慣。
  mysql -u root -p + 回車   -u后跟用戶名,-p表示需要密碼登錄,首次進入mysql用root用戶(輸入root用戶賬戶的密碼,這個密碼要么是在安裝過程中,要么是使用mysqladmin工具獲得的。)。若進入失敗,原因可能是原始密碼未正確配置,可嘗試用密碼'root'登錄。若仍報錯,可參考如下解決方法:
    http://www.cnblogs.com/kerrycode/p/4368312.html
    http://blog.csdn.net/yangxt/article/details/17200611
    mysql的相關安裝目錄可參考:
    http://www.linuxidc.com/Linux/2014-10/108644.htm
    下面命令嘗試可用:
    mysqladmin -u root -p password + 回車(若之前有密碼,則會顯示在password之后)
    Enter password: 輸入新密碼(不可見)
  mysql> STATUS(\s)  - 列出當前mysql的相關狀態信息
  mysql> SHOW DATABASES;  - 顯示數據庫列表
  mysql> USE DB_name;  - 選中數據庫DB_name
  mysql> SHOW TABLES;  - 顯示DB_name下的TABLES列表
  mysql> CREATE DATABASE DB_name;  - 創建一個新的數據庫,當然,首先你應該以root用戶登錄,普通用戶並沒有創建數據庫的權利
  mysql> GRANT SELECT,INSERT,DELETE,UPDATE ON DB_name TO user_name IDENTIFIED
      > by 'user_psd';  - 授予新用戶user_name對於數據庫DB_name的指定權限,登錄密碼user_psd。該用戶擁有的權限:SELECT,INSERT,DELETE,UPDATE
  mysql DB_name -u user_name -p  - 用新創建的用戶user_name登錄數據庫DB_name
  mysql mytest -u root -p  - 用root用戶登錄數據庫DB_name,當我們需要為數據庫DB_name創建新表時,需要root用戶的權限,如下,創建新表的過程:
  mysql> CREATE TABLE employees (
    - > empid int not null,  - 該字段列值非空
    -> lastname varchar(30),
    -> firstname varchar(30),
    -> salary float,
    -> primary key (empid));  - 該字段列值唯一,"primary key" 表示該列是表的主鍵, MySQL將自動索引該列
  mysql> SHOW COLUMNS FROM employees;  - 顯示employees各字段信息(有時我們需要知道表的結構才能確定插入內容的格式)
  mysql> SHOW CREATE TABLE employees;  - 顯示表employees的創建過程,同樣可以查看其內部結構
  mysql> INSERT INTO table VALUES (...);  - 向表table插入一條信息,如:mysql> INSERT INTO employees VALUES (1, 'Blum', 'Rich', 25000.00);
    若:mysql> INSERT INTO employees VALUES (1, 'Blum', 'Barbara', 45000.00);
    則:ERROR 1062 (23000): Duplicate entry '1' for key 1
  mysql> DELETE FROM employees WHERE empid = 1;  - 刪除empid = 1的那條信息
  mysql> DELETE FROM employees;  - 刪除指定數據庫表employees的所有項
  mysql> SELECT * FROM employees;  - 查詢表employees的所有字段內容,SELECT為查詢命令
  mysql> SELECT datafields FROM table;  - 查詢字段列表datafields指定的內容(個字段間用“,”分割)。常用的三個過濾器修飾符如下:
    WHERE:顯示符合特定條件的數據行子集。如:mysql> SELECT * FROM employees WHERE salary > 40000;
    ORDER BY:以指定順序顯示數據行。
    LIMIT:只顯示數據行的一個子集。
  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排序查詢表employees1
  mysql> SELECT * FROM employees1 WHERE salary LIKE '6%';  - 限制salary為數字6開頭的項,LIKE字句可以代替“=”使用
  mysql> exit/quit  - 退出數據庫軟件

2. 新建數據庫之后的相關操作:
  ALTER:
    mysql> ALTER TABLE table_name ...;  - 創建表之后,有時我們需要對表的結構進行修改,就用這個作為命令頭部
    mysql> ALTER TABLE table_name RENAME (AS) table_new_name;  - 表重命名
    mysql> ALTER TABLE table_name ADD 列名 列數據類型 [AFTER 插入位置];  - 在表中新增一個字段信息
    mysql> ALTER TABLE table_name CHANGE 列名稱 列新名稱 新數據類型;  - 指定列重命名
    mysql> ALTER TABLE table_name DROP 列名稱;  - 刪除指定列
  DROP:
    mysql> DROP TABLE table_name;  - 刪除指定表
    mysql> DROP DATABASE database_name;  - 刪除指定數據庫
    mysqladmin -u root -p drop database_name;  - 同樣可以使用mysqladmin命令在mysql軟件之外刪除指定數據庫
  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';  - 限定條件

3. 數據庫表間數據復制:http://www.jb51.net/article/47562.htm
  同一數據庫表間復制:
    INSERT (INTO) table1 select * from table2;  - 完全復制(mysql測試可用)
    INSERT (INTO) table1 select distinct * from table2;  - 不復制重復紀錄(mysql測試不可用)
    INSERT (INTO) table1 select top 5 * from table2;  - 前五條紀錄(mysql測試不可用)
  跨數據庫表間復制:
    INSERT (INTO) (current.)table1 select * from src_database.table2;  - 完全復制
    INSERT (INTO) (current.)table1 select distinct * from src_database.table2;  - 不復制重復紀錄
    INSERT (INTO) (current.)table1 select top 5 * from src_database.table2;  - 前五條紀錄
  若table1不存在,則首先應該創建表,並使其結構與src_database結構相同方可copy:
    CREATE TABLE table1 LIKE (src_database.)table2;  - +(src_database.)取決於是否在同一個數據庫
    INSERT table1 SELECT * FROM (src_database.)table2;

4. 數據庫重命名的幾種方法:http://www.cnblogs.com/allenhua/p/5393189.html
  以方法四為例(mysqldump導出數據再導入):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. 數據庫用戶權限相關:
  mysql> GRANT ALL PRIVILEGES ON mytest1.* TO test@localhost IDENTIFIED BY 'test';  - 授予用戶test對於數據庫mytest1的所有權限
  mysql> GRANT SELECT, INSERT, DELETE,... ON mytest1.* TO test@localhost IDENTIFIED BY 'test';  - 授予用戶test指定權限
  mysql> DELETE FROM user WHERE user = 'test';  - 刪除用戶test
  mysql> FLUSH PRIVILEGES;  - 刷新各用戶權限
  mysql> select * from user;  - 查詢所有用戶的權利

6. 多表查詢:
  mysql> SELECT salary FROM employees1
    -> UNION (ALL)
    -> SELECT salary FROM employees2;  - 合並employees1與employees2兩表salary結果,無重復。+(ALL)全列出可重復
      +--------+
      | salary |
      +--------+
      | 4500 |
      | 5500 |
      | 6500 |
      | 7500 |
      | 8500 |
      | 9500 |
      | 10500 |
      | 11500 |
      +--------+
  三種JOIN查詢方式:http://www.runoob.com/mysql/mysql-join.html

    兩個實例數據庫結構如下:
    mysql> SELECT * FROM tcount_tbl;
    +---------------+--------------+
    | runoob_author | runoob_count |
    +---------------+--------------+
    | 菜鳥教程     |   10   |
    | RUNOOB.COM |   20   |
    | Google     |   22   |
    +---------------+--------------+
    mysql> SELECT * from runoob_tbl;
    +-----------+---------------+---------------+-----------------+
    | runoob_id | runoob_title | runoob_author | submission_date |
    +-----------+---------------+---------------+-----------------+
    | 1     | 學習 PHP  | 菜鳥教程   | 2017-04-12 |
    | 2     | 學習 MySQL | 菜鳥教程   | 2017-04-12 |
    | 3     | 學習 Java  | RUNOOB.COM | 2015-05-01 |
    | 4     | 學習 Python | RUNOOB.COM | 2016-03-06 |
    | 5     | 學習 C   | FK        | 2017-04-05 |
    +-----------+---------------+---------------+-----------------+
    INNER JOIN(內連接,或等值連接):獲取兩個表中字段匹配關系的記錄

                
      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;
      等價於:
      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 | 菜鳥教程 | 10 |
    --> | 2 | 菜鳥教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      +-------------+-----------------+----------------+
    LEFT JOIN(左連接):獲取左表所有記錄,即使右表沒有對應匹配的記錄

                
      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 | 菜鳥教程 | 10 |
    --> | 2 | 菜鳥教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      | 5 | FK | NULL |
      +-------------+-----------------+----------------+
    RIGHT JOIN(右連接):與 LEFT JOIN 相反,用於獲取右表所有記錄,即使左表沒有對應匹配的記錄

                
      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 | 菜鳥教程 | 10 |
    --> | 2 | 菜鳥教程 | 10 |
      | 3 | RUNOOB.COM | 20 |
      | 4 | RUNOOB.COM | 20 |
      | NULL | NULL | 22 |
      +-------------+-----------------+----------------+


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