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- Explain Prefix Indexes in MySQL and their trade-offs.
- Prefix index is used in MySQL to optimize query for long string columns. 1) Reduce index size and improve query speed. 2) It may lead to a decrease in selectivity and is not applicable to ORDERBY or GROUPBY. 3) Selecting the appropriate prefix length requires testing and adjustment to balance performance and selectivity.
- Mysql Tutorial . Database 316 2025-04-04 00:10:51
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- How does InnoDB perform crash recovery?
- InnoDB achieves crash recovery through the following steps: 1. Log playback: read redolog and apply modifications that are not written to the data file to the data page. 2. Roll back uncommitted transactions: Through undolog, roll back all uncommitted transactions to ensure data consistency. 3. Dirty page recovery: handles dirty page writing that is not completed before crash to ensure data integrity.
- Mysql Tutorial . Database 407 2025-04-04 00:06:30
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- What is a covering index in MySQL?
- Overriding indexes can significantly improve MySQL query performance. 1) Overwrite index is defined as an index containing all columns required for query, reducing I/O operations. 2) Its working principle uses the B-Tree structure to directly obtain data from the index to avoid returning to tables. 3) Basic usages such as SELECTusername, emailFROMusersWHEREusername='alice', advanced usages can be used for complex query and aggregation operations.
- Mysql Tutorial . Database 239 2025-04-04 00:03:41
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- How to interpret MySQL EXPLAIN output for query optimization? (key types like ref, range, index, ALL)
- MySQL's EXPLAIN command is used to show the query execution plan and help optimize queries. 1) The ref type is used for index search, 2) The range type is used for range query, 3) The index type represents full index scan, 4) The ALL type represents full table scan, which is the slowest.
- Mysql Tutorial . Database 764 2025-04-03 00:18:30
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- What is index merge optimization in MySQL?
- Index merge optimization is a query optimization strategy for MySQL that allows multiple indexes to be used in a single query to speed up data retrieval. Its working principle includes: 1. Index merge intersection, used for AND relationship conditions; 2. Index merge union, used for OR relationship conditions; 3. Index merge sort, used for OR conditions that need to be sorted. This optimization can significantly reduce the number of rows scanned, thereby improving query performance.
- Mysql Tutorial . Database 449 2025-04-03 00:16:31
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- How does index cardinality affect query performance in MySQL?
- Index cardinality has a significant impact on MySQL query performance. High cardinality indexes can locate data faster and optimize queries; low cardinality indexes may lead to full table scanning. Query performance can be effectively improved by regularly updating statistics, selecting the appropriate index type, avoiding over-index and using over-index.
- Mysql Tutorial . Database 376 2025-04-03 00:09:10
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- How does connection pooling improve MySQL performance?
- Connection pooling can significantly improve MySQL performance. 1) It reduces the number of connection creation and closing times by pre-creating and maintaining a set of connections. 2) Initialize the connection pool when the application starts, get the connection from the pool when requested, and return it after use. 3) Configuring the connection pool size, setting timeouts and health checks, managing transactions, and ensuring code readability and maintenance are best practices for implementation.
- Mysql Tutorial . Database 337 2025-04-03 00:02:50
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- What is the MySQL Slow Query Log and how do you use it effectively?
- MySQLSlowQueryLog is a tool for recording queries whose execution time exceeds a set threshold. 1) Enable slow query logs and set thresholds; 2) View slow query log files; 3) Use mysqldumpslow tool to analyze slow queries; 4) Clean the log files regularly and adjust the thresholds; 5) Improve database performance by analyzing logs and using indexes.
- Mysql Tutorial . Database 1026 2025-04-03 00:01:31
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- Explain MySQL semi-synchronous replication.
- MySQL semi-synchronous replication balances data consistency and performance by waiting for at least one slave library to confirm before the master library returns to the client. 1) Enable semi-synchronous replication on the main library: SETGLOBALrpl_semi_sync_master_enabled=1;2) Enable semi-synchronous replication on the slave library: SETGLOBALrpl_semi_sync_slave_enabled=1; This method not only improves data consistency, but does not seriously affect performance like synchronous replication.
- Mysql Tutorial . Database 898 2025-04-02 19:21:10
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- How do you detect and handle deadlocks in MySQL?
- Methods for detecting and handling deadlocks in MySQL include: 1. Use the SHOWENGINEINNODBSTATUS command to view deadlock information; 2. Use the data_locks table of performance Schema to monitor the lock status; 3. Ensure that transactions acquire locks in the same order to avoid holding locks for a long time; 4. Optimize transaction design and lock strategies, and adjust the deadlock detection switch if necessary.
- Mysql Tutorial . Database 828 2025-04-02 19:13:10
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- Explain different types of MySQL indexes (B-Tree, Hash, Full-text, Spatial).
- MySQL supports four index types: B-Tree, Hash, Full-text, and Spatial. 1.B-Tree index is suitable for equal value search, range query and sorting. 2. Hash index is suitable for equal value searches, but does not support range query and sorting. 3. Full-text index is used for full-text search and is suitable for processing large amounts of text data. 4. Spatial index is used for geospatial data query and is suitable for GIS applications.
- Mysql Tutorial . Database 953 2025-04-02 19:05:10
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- Difference between clustered index and non-clustered index (secondary index) in InnoDB.
- The difference between clustered index and non-clustered index is: 1. Clustered index stores data rows in the index structure, which is suitable for querying by primary key and range. 2. The non-clustered index stores index key values and pointers to data rows, and is suitable for non-primary key column queries.
- Mysql Tutorial . Database 980 2025-04-02 18:25:11
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- Explain InnoDB Full-Text Search capabilities.
- InnoDB's full-text search capabilities are very powerful, which can significantly improve database query efficiency and ability to process large amounts of text data. 1) InnoDB implements full-text search through inverted indexing, supporting basic and advanced search queries. 2) Use MATCH and AGAINST keywords to search, support Boolean mode and phrase search. 3) Optimization methods include using word segmentation technology, periodic rebuilding of indexes and adjusting cache size to improve performance and accuracy.
- Mysql Tutorial . Database 1186 2025-04-02 18:09:10
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- What are the key features and improvements in the latest version of MySQL?
- MySQL 8.0 enhances performance and security with features like atomic DDL, roles, and improved JSON support, aiding developers with large datasets.Character count: 159
- Mysql Tutorial . Database 541 2025-03-31 11:04:27
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