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Technical Articles

Database

Mysql Tutorial

How to optimize mysql memory? What are the key parameters?

The core of MySQL memory optimization is to rationally configure key parameters to improve performance. 1. Adjust innodb_buffer_pool_size to 50%~80% of physical memory. For example, the 32GB server can be set to 24GB, and combine multiple instances to reduce contention. 2. Control the connection memory. The thread_stack is recommended to not be less than 192KB. The sort_buffer_size is set to 1MB~2MB to avoid memory waste. 3. Configure the global memory parameters tmp_table_size and max_heap_table_size to 128M to avoid temporary table drops. 4. Maintain the monitoring tool through SHOWENGINEINNODBSTATUS and monitoring tools

Jun 04, 2025 pm 06:21 PM

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What is mysql transaction? How to ensure data consistency?

The ACID characteristics of a transaction refer to atomicity, consistency, isolation and persistence. Atomicity ensures that all operations in a transaction are done or not; consistency ensures that the database is transferred from one consistent state to another; isolation prevents mutual interference when multiple transactions are executed concurrently; persistence ensures that the results of the transaction are permanently saved after the transaction is committed. Transactions ensure data consistency through redolog, undolog and lock mechanisms. RedoLog is used for crash recovery, UndoLog supports rollback and MVCC, and the lock mechanism controls concurrent access to avoid dirty reading, non-repeatable reading and phantom reading. Correct use of transactions requires reasonable control of transaction boundaries and the appropriate isolation level is selected. For example, READCOMMITTED is suitable for most scenarios, REPEA

Jun 04, 2025 pm 06:18 PM

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What are the mysql data types? How to choose the right type?

Choosing the right MySQL data type can save storage space, improve query performance and ensure data accuracy. Common data types are divided into numerical types (such as INT, DECIMAL), string types (such as CHAR, VARCHAR), and date and time types (such as DATE, DATETIME, TIMESTAMP). Several key points should be followed when choosing: 1. Save storage space, such as TINYINT in the status field; 2. Improve query efficiency, give priority to the use of fixed-length types; 3. Avoid accuracy loss, use DECIMAL in the amount field; 4. Pay attention to the difference in default behavior, such as TIMESTAMP automatically handles time zones. Common scenario recommendations: Use INTUNSIGNED or BIGINT for user ID,

Jun 04, 2025 pm 06:15 PM

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Command to create a table in mysql Detailed explanation of the new data table command

Create tables in MySQL using the CREATETABLE command. The specific steps include: 1) Defining the table name and column, such as CREATETABLEusers(idINTAUTO_INCREMENTPRIMARYKEY,usernameVARCHAR(50)NOTNULLUNIQUE,emailVARCHAR(100)NOTNULLUNIQUE,passwordVARCHAR(255)NOTNULL,created_atTIMESTAMPDEFAULTCURRENT_TIMESTAMP); 2) Add constraints, such as FOREIGNKEY; 3)

Jun 04, 2025 pm 06:12 PM

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Resolve errors when PHP updates MySQL database data

To resolve the errors in PHP when updating MySQL database data, you can use the following steps: 1. Check for SQL syntax errors and ensure that the table name, field name and WHERE conditions are correct. 2. Verify the database connection configuration to ensure that the user name and password are correct. 3. Confirm that the database user has sufficient permissions. 4. Use preprocessing statements to prevent SQL injection and reduce syntax errors. 5. Application transactions ensure data consistency. 6. Improve the error handling mechanism to avoid program crashes. 7. Regularly update the database configuration. 8. Consider using ORM tools to simplify code and reduce errors.

Jun 04, 2025 pm 06:09 PM

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MySQL command line operation list Complete guide to using terminal mode

Using the MySQL database in terminal mode can be performed through the following steps: 1. Connect to the MySQL server and use the command mysql-uusername-p. 2. Create databases and tables, using the CREATEDATABASE and CREATETABLE commands. 3. Execute the SQL script and import the script using the source command. 4. Query the data and use DESCRIBE or SHOWCREATETABLE to view the table structure. 5. Optimize queries and use EXPLAIN to analyze the execution plan. 6. Process large-scale data, using LIMIT and OFFSET to process it in batches. Through these steps, the database can be managed and operated efficiently.

Jun 04, 2025 pm 06:06 PM

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A complete list of commonly used commands for mysql databases 30 most commonly used commands for administrators

MySQL administrators should master 30 key commands: 1. SHOWDATABASES view all databases; 2. USE SHOWTABLES view tables in the database; 3. DESCRIBE view table structure; 4. INSERT/UPDATE/DELETE operation data; 5. SELECT query data; 6. mysqldump backup and recovery database; 7. EXPLAIN analysis query execution plan; 8. CREATEUSER/GRANT/REVOKE/DROPUSER manage users and permissions; 9. SHOWPROCESSLIST/SHOWENGINE/CHECK/REPAIR/OPTIM

Jun 04, 2025 pm 06:03 PM

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Create tables and add new data in mysql. Complete process of creating table inserts

The steps to create a table and insert data in MySQL are as follows: 1. Create a table: Use the CREATETABLE statement to define the table name and structure, such as CREATETABLEusers(...). 2. Insert data: Use the INSERTINTO statement to add data, such as INSERTINTOusers(...)VALUES(...). Mastering these operations can improve database management skills and manage data efficiently in real projects.

Jun 04, 2025 pm 06:00 PM

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How to create a table in mysql

When creating tables in MySQL, you need to pay attention to the following points: 1. Select the appropriate data type, such as VARCHAR (50) for the user name, and VARCHAR (100) for the mailbox. 2. Use constraints such as PRIMARYKEY, UNIQUE, NOTNULL to maintain data integrity. 3. Add indexes to commonly used query fields to improve query performance. 4. Consider the scalability of the table and reserve future expansion requirements. 5. Use AUTO_INCREMENT to generate a unique primary key to improve insertion efficiency.

Jun 04, 2025 pm 05:57 PM

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MySQL Views: Performances concerns

MySQLviewscanimpactperformancenegativelyifnotmanagedcorrectly.1)Viewsarecomputedon-the-fly,leadingtopotentialslowdownswithcomplexqueries.2)Properindexingofunderlyingtablesiscrucialforefficiency.3)Simplifyingviewsandhandlingcomplexityattheapplicationl

Jun 04, 2025 am 12:17 AM

MySQL Triggers: Are they secured?

MySQLtriggerscanbesecuredwithcarefulmanagement.1)Usetheprincipleofleastprivilege.2)Conductregularaudits.3)Implementsecurecodingpractices.4)Enhancemonitoringandlogging.Thesestrategieshelpmitigaterisksassociatedwithtriggers.

Jun 04, 2025 am 12:17 AM

MySQL Views: is possible to index a View?

MySQL does not support creating indexes for views directly. Performance can be improved by: 1. Create and regularly update materialized view charts and index them; 2. Create indexes on tables that view dependencies; 3. Optimize query statements to improve efficiency.

Jun 04, 2025 am 12:16 AM

What is the Maximum Number of Triggers Allowed per Table in MySQL?

MySQLallowsuptosixtriggerspertable,derivedfromthreeoperations(INSERT,UPDATE,DELETE)eachhavingBEFOREandAFTERtriggers.Usingtriggerseffectivelyinvolveskeepingthemsimple,consideringperformanceimpacts,thoroughdocumentation,andextensivetestingtomanagedatab

Jun 04, 2025 am 12:16 AM

How Many BEFORE and AFTER Triggers Can I Define in MySQL?

In MySQL, each table can define a BEFORE and an AFTER trigger for each specific operation (INSERT, UPDATE, DELETE). This means that for a table you can have the following combinations: 1.BEFOREINSERT, 2.AFTERINSERT, 3.BEFOREUPDATE, 4.AFTERUPDATE, 5.BEFOREDELETE, 6.AFTERDELETE.

Jun 04, 2025 am 12:12 AM