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  • Choosing Appropriate Data Types in MySQL
    Choosing Appropriate Data Types in MySQL
    Selecting the right data type in MySQL can improve performance and storage efficiency. 1. Select fixed-length CHAR or variable-length VARCHAR according to the field length, and use TINYINT in the status field first; 2. Use DATE, DATETIME or TIMESTAMP as required for the time type to avoid using INT to store timestamps; 3. Use TEXT/BLOB to give priority to VARCHAR to reduce I/O overhead; 4. Use ENUM type or independent table to enumerate values to improve data standardization and query efficiency.
    Mysql Tutorial . Database 291 2025-07-13 02:53:00
  • what is a covering index in mysql
    what is a covering index in mysql
    Overwrite indexes in MySQL are indexes that contain all columns required for a query, thus avoiding access to actual table data. It reduces I/O by eliminating table searches and improves query speed. For example, when SELECTidFROMusersWHEREstatus='active' is executed, if there is a composite index of (status,id), it constitutes an overlay index. The best scenarios for using overlay indexes include: 1. Query involves only a small number of columns; 2. Aggregated queries such as COUNT or SUM; 3. High-frequency conditional queries. To identify an overwrite index opportunity, view the Extra column in the EXPLAIN output. If “Usingindex” is displayed, the overwrite index is used. All the query should be included when designing
    Mysql Tutorial . Database 577 2025-07-13 02:47:50
  • how to create user in mysql
    how to create user in mysql
    To create MySQL users, you need to pay attention to syntax and permission settings. First, use CREATEUSER to specify the user name, host name and password, such as CREATEUSER'testuser'@'localhost'IDENTIFIEDBY'password123'; if you want to allow any IP to log in, change localhost to %. Secondly, the permissions are allocated through the GRANT command, such as GRANTALLPRIVILEGESONtestdb.*TO'testuser'@'localhost'; Common permissions include SELECT, INSERT, UPDATE, DELETE, CREATE, DROP and AL
    Mysql Tutorial . Database 641 2025-07-13 02:47:01
  • mysql user defined functions (udf)
    mysql user defined functions (udf)
    MySQLUDF is a user-defined function written in C/C and compiled into a shared library and registered with MySQL for efficient implementation of specific logic. 1. UDF is suitable for computing operations such as string processing, mathematical operations, etc., and the execution efficiency is higher than that of stored procedures; 2. The creation steps include writing code, compiling into .so files, placing them in MySQL accessible directory, and registering and using them through CREATEFUNCTION; 3. When using them, you need to pay attention to compatibility, stability, debugging difficulty and deployment complexity. It is recommended to only be used when high-performance requirements and SQL is difficult to implement; 4. Alternative solutions include storage functions, triggers, application layer processing or MySQL plug-in system, which can be selected according to actual needs.
    Mysql Tutorial . Database 677 2025-07-13 02:45:20
  • mysql date_add function
    mysql date_add function
    MySQL's DATE_ADD function is used to add a specified time interval to a date or time value. Its basic syntax is DATE_ADD(date,INTERVALexprunit), where date is the original date or time, INTERVAL is the keyword, expr is the increased number, and unit is the time unit such as DAY, MONTH, etc. 1. It is often used to calculate future time points, such as one day's reminder after registration, member validity period, etc.; 2. It can be used in combination with other functions, such as using CURDATE() to obtain yesterday's data, or NOW() to query future appointments; 3. When using it, you need to pay attention to the correctness of the date format, unit spelling, negative number use and cross-month/year boundary issues. Mastering this function helps
    Mysql Tutorial . Database 658 2025-07-13 02:45:01
  • Using the MySQL Shell for administration and scripting
    Using the MySQL Shell for administration and scripting
    The method of MySQLShell to connect to the database is to use the mysqlsh command to start and enter connection information, or directly specify user@host:port on the command line; 1. The startup method is flexible, supports interactive input or directly specifying parameters; 2. Pay attention to SSL settings and authentication methods, especially when remote connections, to ensure the correct permissions and passwords; 3. After entering the shell, it is SQL mode by default, and can perform regular SQL operations; 4. Support switching to JS or Python mode to write complex scripts to realize automated tasks; 5. Script writing requires attention to mode selection, output format, exception handling and file saving; 6. Provide practical tips, such as viewing the current mode, switching paths, multi-instance connections, and checking help articles
    Mysql Tutorial . Database 629 2025-07-13 02:43:51
  • mysql use random order
    mysql use random order
    Using ORDERBYRAND() to implement random sorting is suitable for small data volumes or temporary requirements, but has poor performance. The problem is that the full table scans and generates random numbers for each row and then sorts it, resulting in extremely low efficiency when queries are large data or high-frequency. Alternatives include: 1. Pre-random numbering; 2. Random ID range sampling; 3. Pagination cache; 4. Maintaining random pools separately. Which method to choose depends on business requirements and data structure.
    Mysql Tutorial . Database 777 2025-07-13 02:32:10
  • mysql transaction commit rollback
    mysql transaction commit rollback
    Transactions are the mechanism in MySQL to ensure data consistency, and have ACID characteristics (atomicity, consistency, isolation, and persistence). The core is to ensure that a set of SQL operations are either successful or all failed. commit is used to confirm all changes in the transaction and write to the database, and rollback is used to undo operations in the transaction and restore to the initial state. Note when using: 1. The default automatic commit needs to be closed for manual control; 2. Transactions cannot be nested, but partial rollback can be simulated by save points; 3. Long transactions affect performance as short as possible; 4. DDL statements will implicitly submit transactions; 5. Forgot to commit or the exception is not processed may lead to lock waiting or data inconsistency; 6. Multi-connection operations need to pay attention to transaction independence. Master these
    Mysql Tutorial . Database 223 2025-07-13 02:26:11
  • how to use sqlalchemy with mysql
    how to use sqlalchemy with mysql
    The steps to operate MySQL using SQLAlchemy are as follows: 1. Install dependencies and configure connections; 2. Define the model or use native SQL; 3. Perform database operations through session or engine. First, you need to install sqlalchemy and mysql-connector-python, and then create an engine in the format create_engine('mysql mysqlconnector://user:password@host/database_name'). Then you can describe the table structure by defining the model class and use Base.metadata.create_all(engine)
    Mysql Tutorial . Database 665 2025-07-13 02:24:30
  • mysql temporary table vs memory table
    mysql temporary table vs memory table
    Temporary tables are tables with limited scope, and memory tables are tables with different storage methods. Temporary tables are visible in the current session and are automatically deleted after the connection is disconnected. Various storage engines can be used, which are suitable for saving intermediate results and avoiding repeated calculations; 1. Temporary tables support indexing, and multiple sessions can create tables with the same name without affecting each other; 2. The memory table uses the MEMORY engine, and the data is stored in memory, and the restart is lost, which is suitable for cache small data sets with high frequency access; 3. The memory table supports hash indexing, and does not support BLOB and TEXT types, so you need to pay attention to memory usage; 4. The life cycle of the temporary table is limited to the current session, and the memory table is shared by all connections. When choosing, it should be decided based on whether the data is private, whether high-speed access is required and whether it can tolerate loss.
    Mysql Tutorial . Database 554 2025-07-13 02:23:50
  • Securing MySQL installations with SSL/TLS connections
    Securing MySQL installations with SSL/TLS connections
    To configure MySQL's SSL/TLS encrypted connection, first generate a self-signed certificate and correctly configure the server and client settings. 1. Use OpenSSL to generate CA private key, CA certificate, server private key and certificate request, and sign the server certificate yourself; 2. Place the generated certificate file in the specified directory, and configure the ssl-ca, ssl-cert and ssl-key parameters in my.cnf or mysqld.cnf and restart MySQL; 3. Force SSL on the client, restrict users from connecting only through SSL through the GRANTUSAGE command, or specify the --ssl-mode=REQUIRED parameter when connecting; 4. After logging in, execute \s to check SSL status confirmation
    Mysql Tutorial . Database 778 2025-07-13 02:16:02
  • mysql show all tables in database
    mysql show all tables in database
    There are three common ways to view all tables under a database in MySQL. 1. Use USEdatabase_name; execute SHOWTABLES after switching the database; list all tables in the current database; 2. When not switching the database, execute SHOWTABLESFROMdatabase_name; view the tables of the specified database; 3. Query INFORMATION_SCHEMA.TABLES to obtain more detailed table information, such as types and engines, you need to use SELECTtable_name, table_type, engineFROMinformation_schema.tablesWHEREtable_
    Mysql Tutorial . Database 170 2025-07-13 02:13:50
  • Working with spatial data types and functions in MySQL
    Working with spatial data types and functions in MySQL
    MySQL supports spatial data types such as GEOMETRY, POINT, LINESTRING, POLYGON, etc., which can be inserted in WKT format; to create tables with spatial indexes, use SPATIALINDEX and specify engines such as InnoDB; common functions include ST_AsText, ST_GeomFromText, ST_Distance, ST_Contains, etc.; optimization suggestions include adding spatial indexes, avoiding full table scanning, using range filtering, maintaining SRID consistency and combining accurate distance algorithms.
    Mysql Tutorial . Database 318 2025-07-13 02:10:01
  • how to check which storage engine is used in mysql
    how to check which storage engine is used in mysql
    The method of viewing the storage engine of MySQL is as follows: 1. You can use the command SHOWVARIABLESLIKE'default_storage_engine'; 2. You can use the storage engine used to view a certain table to view the storage engine through SHOWCREATETABLE or query information_schema.TABLES; 3. You can use SELECTTABLE_NAME,ENGINEFROMinformation_schema.TABLESWHERETABLE_SCHEMA='your_database'; 4. Other methods include on the command line
    Mysql Tutorial . Database 690 2025-07-13 02:00:35

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