场景:有同事需要把从库中的数据,同步一份到新环境,但发现在主库上执行count语句,和从库上执行count语句得出的结果不同。 解决思路: 在从库上执行show slave status \G ,查看返回结果: *************************** 1. row **************************
场景:有同事需要把从库中的数据,同步一份到新环境,但发现在主库上执行count语句,和从库上执行count语句得出的结果不同。
解决思路:
在从库上执行 show slave status \G ,查看返回结果:
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.1.118
Master_User: bak
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000728
Read_Master_Log_Pos: 586670704
Relay_Log_File: mysqld-relay-bin.002178
Relay_Log_Pos: 457911949
Relay_Master_Log_File: mysql-bin.000709
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_Do_DB: mydb
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1062
Last_Error: Error 'Duplicate entry 'XXXXXXX' for key 2' on query. Default database: 'mydb'. Query: 'INSERT INTO `network` (`uuid`, `machine_name`, `port`, `update_time`) VALUES ('5''
Skip_Counter: 0
Exec_Master_Log_Pos: 457911812
Relay_Log_Space: 20988097167
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: null
1 row in set (0.00 sec)
发现从库在同步时出错,没有能正常同步,解决方法:
第一:停止slave,slave stop;
第二:跳过一条出错的语句:set GLOBAL SQL_SLAVE_SKIP_COUNTER=1;
第三:启动slave,slave start;
第四:使用show slave status \G 查看当前的同步情况,如果Slave_SQL_Running: Yes,则成功,如果Slave_SQL_Running: No,则再次执行一到四。如果不想一次次重复,可以在第二步中跳过多条错误的语句。
最后看看当前从库与主库的时间差:Seconds_Behind_Master: 197011

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.

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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.

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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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