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Technical Articles

Database

Mysql Tutorial

How to implement multi-value association query through FIND_IN_SET?

FIND_IN_SET: Unraveling the mystery of multi-value association query. Many friends will encounter a difficult problem in database operations: How to efficiently handle multi-value association query? For example, a user can have multiple tags. How to find users based on tags? This article will explore in-depth how to use MySQL's FIND_IN_SET function to gracefully solve this problem and reveal the pitfalls and optimization strategies behind it. Let's make it clear first: FIND_IN_SET is not the best solution for handling multi-value correlation queries. It has performance bottlenecks, especially when the data volume is huge. But understanding how it works and limitations is crucial for database design and optimization. It is more suitable for some special scenarios, such as small data volume

Apr 08, 2025 am 09:33 AM

mysql

Configuration and conflict resolution of Galera Cluster multi-master cluster

GaleraCluster is a database cluster architecture based on multi-master replication, with the advantage that all nodes can receive write requests at the same time. When building a Galera cluster, you need to pay attention to: 1. Ensure that the node resources are sufficient and the network is stable; 2. Carefully configure the my.cnf file, especially the wsrep_provider_options and gcache.size parameters; 3. Correctly initialize the cluster and monitor the logs. Even if the configuration is correct, conflicts may occur. They need to be resolved through log analysis and application layer policies, and performance can be improved through network optimization, parameter tuning and application layer optimization. Continuous monitoring and log analysis are key to maintaining Galera clusters.

Apr 08, 2025 am 09:30 AM

mysql tool the difference sql statement concurrent access

Windows System MySQL 8.0 installation-free configuration tutorial

Configuration method for MySQL 8.0 installation-free version under Windows: 1. Unzip the downloaded compressed package to the specified directory; 2. Modify the my-default.ini file, configure basedir, datadir, port, character set and proofreading rules, and create a datadir directory; 3. Use the command line (cmd) to enter the bin directory, execute mysqld--install (optional) and netstartmysql to start the service. After the configuration is successful, you can use the client tool to connect to the database. It is recommended to modify the root password and perform secure configuration, and back up the data regularly.

Apr 08, 2025 am 09:27 AM

mysql windows navicat tool data lost

Explain the difference between Statement-Based Replication (SBR), Row-Based Replication (RBR), and Mixed-Based Replication (MBR).

There are three main ways of replication in MySQL: SBR, RBR and MBR. 1. SBR records SQL statements, which are suitable for standard operations, but may cause data inconsistency. 2. RBR records data changes to ensure consistency, but the log is large. 3.MBR combines the two and selects the method according to the SQL type, which is flexible but complex. Consistency, performance, and complexity are considered when choosing.

Apr 08, 2025 am 12:04 AM

mysql copy Database replication

Compare and contrast InnoDB and MyISAM storage engines (features, locking, transactions).

InnoDB is suitable for highly concurrency and transaction-intensive applications, while MyISAM is suitable for read-intensive applications. 1) InnoDB supports transaction and row-level locks, and is suitable for high-concurrency scenarios such as e-commerce platforms. 2) MyISAM does not support transactions, but reads fast, and is suitable for read-intensive applications such as blog systems.

Apr 08, 2025 am 12:03 AM

innodb myisam

Explain B-Tree indexes in MySQL and how they work.

B-Tree indexes in MySQL accelerate data retrieval by creating indexes on columns of tables, significantly reducing the amount of data that needs to be scanned during queries, thereby improving query performance. 1) Create a B-Tree index using a CREATEINDEX statement, such as CREATEINDEXidx_ageONemployees(age). 2) The working principle of B-Tree index includes structure, query process, and automatic adjustment during insertion and deletion. 3) Use the EXPLAIN command to debug the problem that the index is not used. 4) Performance optimization suggestions include selecting appropriate columns, using overlay indexes, regular maintenance, as well as maintaining code readability and testing and monitoring.

Apr 08, 2025 am 12:02 AM

mysql index B-Tree

Explain index merge optimization in MySQL.

Index merging is a MySQL query optimization strategy that improves query efficiency by leveraging multiple indexes. 1) Index scan: MySQL scans each of the indexes involved separately to obtain records that meet the conditions. 2) Result merge: merge the results through Union, Intersection or Sort-Union. 3) Result filtering: The combined results are further filtered to ensure that all query conditions are met.

Apr 08, 2025 am 12:01 AM

mysql optimization Index Merge

Explain MySQL Query Cache (and why it's often disabled/deprecated).

MySQL query cache is often disabled or even marked as deprecated because it performs poorly in environments with high concurrency and frequent data updates. 1) Query cache improves performance by storing the results of SELECT statements, but depends on data stability. 2) In modern MySQL versions, query cache has been abandoned, and alternatives such as InnoDB buffer pooling, query rewriting and index optimization are recommended.

Apr 07, 2025 am 12:13 AM

Explain explicit table locking (LOCK TABLES) versus InnoDB row-level locking.

The difference between explicit table locking in MySQL and InnoDB row-level locking is the lock granularity and applicable scenarios. Explicit table locking locks the entire table through the LOCKTABLES statement, suitable for backup or batch updates; InnoDB row-level locking locks affected rows through transactions and indexes, suitable for high concurrency environments.

Apr 07, 2025 am 12:12 AM

row lock mysql lock

How do you analyze a MySQL query execution plan using EXPLAIN?

The EXPLAIN command is used to show how MySQL executes queries and helps optimize performance. 1) EXPLAIN displays the query execution plan, including access type, index usage, etc. 2) By analyzing the EXPLAIN output, bottlenecks such as full table scanning can be found. 3) Optimization suggestions include selecting the appropriate index, avoiding full table scanning, optimizing join query and using overlay indexes.

Apr 07, 2025 am 12:10 AM

Query the execution plan

What are prefix indexes in MySQL and when are they useful/problematic?

Prefix indexing is a tool in MySQL used to optimize query performance, reducing the index size by indexing the first N characters of a string field. When using prefix indexes, you need to pay attention to: 1. Select the appropriate prefix length, 2. Avoid query conditions involving the middle or back characters of the string, 3. Use in combination with other index types, 4. Regularly monitor and adjust the index strategy.

Apr 07, 2025 am 12:08 AM

mysql index prefix index

How can MySQL Query Optimizer Hints be used (e.g., USE INDEX, FORCE INDEX)?

The methods for using MySQL query optimizer tips are: 1. Use USEINDEX prompt optimizer to give priority to the specified index; 2. Use FORCEINDEX to force the optimizer to use the specified index. By adding these prompts to SQL queries, query performance can be significantly improved, but you need to avoid selecting wrong indexes and overuse of FORCEINDEX, and debugging through EXPLAIN statements.

Apr 07, 2025 am 12:06 AM

mysql optimization Query Tips

Strategies for optimizing COUNT(*) queries on large InnoDB tables.

Optimizing COUNT(*) queries for InnoDB tables can be done by the following methods: 1. Using approximation values to estimate the total number of rows through random sampling; 2. Creating indexes to reduce the scan range; 3. Using materialized views, pre-calculate the results and refresh them regularly to improve query performance.

Apr 06, 2025 am 12:10 AM

mysql optimization

How does innodb_flush_log_at_trx_commit affect performance and durability?

The value of innodb_flush_log_at_trx_commit determines how InnoDB handles redolog's flush operation: 1. When the value is 1, the disk is flushed every transaction commit to ensure the highest data durability, but may affect performance. 2. When the value is 0, refresh it once every second to improve performance but may lose data for the last second. 3. When the value is 2, it is written to the operating system cache. The performance is between the first two, but there is still a risk of data loss.

Apr 06, 2025 am 12:07 AM

Database performance