mysql5.6.15忘记数据库的root密码:[root@oraserver139 ~]# mysql -uroot -pEnter password: ERROR 1045 (28000): Access denied
mysql5.6.15忘记数据库的root密码:
[root@oraserver139 ~]# mysql -uroot -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
查看当前安装的mysql版本:
root@oraserver139 ~]# rpm -qa | grep MySQL
MySQL-server-5.6.15-1.el6.x86_64
MySQL-client-5.6.15-1.el6.x86_64
MySQL-shared-compat-5.6.15-1.el6.x86_64
MySQL-devel-5.6.15-1.el6.x86_64
perl-DBD-MySQL-4.022-1.el6.rfx.x86_64
停止mysql服务:
[root@oraserver139 ~]# service mysql stop
Shutting down MySQL.. SUCCESS!
进入到skip-grant-tables模式:
[root@oraserver139 ~]# mysqld_safe --skip-grant-tables
140211 15:37:49 mysqld_safe Logging to '/var/lib/mysql/oraserver139.err'.
140211 15:37:49 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
现在就不需要密码就可以进入mysql了:
[root@oraserver139 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.15 MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
进入mysql系统数据库:
mysql> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
修改root账户密码:
mysql> update user set password=password("12345") where user="root";
Query OK, 4 rows affected (0.02 sec)
Rows matched: 4 Changed: 4 Warnings: 0
刷新权限:
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
停止mysql进程:
[1]+ Stopped mysqld_safe --skip-grant-tables
启动mysql:
[root@oraserver139 ~]# service mysql start
Starting MySQL SUCCESS!
使用刚才修改的密码进入mysql:
[root@oraserver139 ~]# mysql -uroot -p12345
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.15
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show databases;
ERROR 1820 (HY000): You must SET PASSWORD before executing this statement
mysql> SET PASSWORD = PASSWORD('12345');
Query OK, 0 rows affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.00 sec)
修改完成;

ACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.

MySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.

MySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.

MySQL is an efficient relational database management system suitable for storing and managing data. Its advantages include high-performance queries, flexible transaction processing and rich data types. In practical applications, MySQL is often used in e-commerce platforms, social networks and content management systems, but attention should be paid to performance optimization, data security and scalability.

The relationship between SQL and MySQL is the relationship between standard languages and specific implementations. 1.SQL is a standard language used to manage and operate relational databases, allowing data addition, deletion, modification and query. 2.MySQL is a specific database management system that uses SQL as its operating language and provides efficient data storage and management.

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB


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