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Home

Technical Articles

Database

Mysql Tutorial

MySQL Enterprise Edition vs Community Edition Features

MySQLCommunityEdition is a free, open source version suitable for medium-sized applications; EnterpriseEdition is a paid version that provides additional tools, plug-ins and official support. 1.EnterpriseEdition includes performance monitoring tools (such as MySQLEnterpriseMonitor), online backup tools (MySQLEnterpriseBackup), and security enhancements (MySQLEnterpriseSecurity), while CommunityEdition lacks these advanced tools. 2.EnterpriseEdition provides database auditing and fine-grained access

Aug 13, 2025 am 10:10 AM

How to implement a search with multiple optional parameters in MySQL

UseconditionalWHEREclauseswithOR?ISNULLtohandleoptionalparametersbyallowingeachfiltertobeskippediftheparameterisNULL,ensuringsafepreparedstatementusage.2.BuilddynamicSQLinapplicationcodetoincludeonlytheprovidedfilters,improvingindexutilizationandquer

Aug 13, 2025 am 10:09 AM

MySQL Data Dictionary and Information Schema Exploration

Information Schema is a system database provided by MySQL, which contains read-only virtual tables, used to display metadata, such as querying which tables the database can execute SELECTTABLE_NAMEFROMinformation_schema.TABLESWHERETABLE_SCHEMA='your_database_name'; Common uses include: 1. Use COLUMNS table to check column information; 2. Use STATISTICS table to check index information; 3. Use VIEWS table to check view definitions; 4. Use TABLES and COLLATIONS tables to check character sets and sorting rules. Data Dictionary (DataD

Aug 13, 2025 am 09:09 AM

How to schedule a job using the MySQL event scheduler

To use the MySQL event scheduler to schedule tasks, you must first enable the event scheduler. You can turn on by executing SETGLOBALevent_scheduler=ON; and it is recommended to add event_scheduler=ON to the configuration file to persist. Then create a scheduled event, such as performing a log cleanup task once a night at midnight every day, and use a CREATEEVENT statement definition, such as CREATEEVENTIFNOTEXISTSdaily_log_cleanupONSCHEDULEEVERY1DAY1DAYSTARTSTIMESTAMP(CURDATE() INTERVAL1DAY,'00:00:

Aug 13, 2025 am 07:12 AM

How to configure MySQL to run on a different port?

Modify the MySQL running port to edit the configuration file my.cnf (Linux/macOS) or my.ini (Windows), and set port=new port number under the [mysqld] paragraph; 2. Restart MySQL service after saving the file: Linux uses sudosystemctlrestartmysql, Windows uses netstopmysql and netstartmysql; 3. Verify that the port has taken effect through sudonestat-tulnp|grepmysqld or mysql-uroot-p-P new port-host=127.0.0.1; 4. Ensure that the firewall opens the new port

Aug 13, 2025 am 06:07 AM

mysql 端口配置

How to analyze and repair tables in MySQL?

Analyzeandrepairtableswhenqueriesslowdown,errorsindicatecorruption,oraftercrashes,especiallyforMyISAMtables.2.RunANALYZETABLEtoupdateindexstatisticsandimprovequeryoptimizerdecisions,lockingthetablebriefly.3.UseREPAIRTABLEtofixMyISAMcorruption,withopt

Aug 13, 2025 am 04:32 AM

How to rollback a transaction in MySQL

To roll back transactions in MySQL, you must use a transaction-enabled storage engine such as InnoDB. 1. Confirm the table to use InnoDB: SHOWCREATETABLEyour_table_name; if not InnoDB, execute ALTERTABLEyour_table_nameENGINE=InnoDB; 2. Start the transaction explicitly: use STARTTRANSACTION or BEGIN; 3. Execute SQL statements such as UPDATEaccountsSETbalance=balance-100WHEREuser_id=1; and UPDATEaccountsSETbalance

Aug 13, 2025 am 03:26 AM

mysql 事務(wù)回滾

How to rename a table in MySQL?

TorenameatableinMySQL,usetheRENAMETABLEstatement,whichchangesthetable'snamebyupdatingmetadatawithoutalteringthedata,ensuringafastoperation;forexample,executeRENAMETABLEold_table_nameTOnew_table_nametorenameasingletable,orincludemultiplerenamesinoneco

Aug 13, 2025 am 03:03 AM

mysql 重命名表

How to use self join in MySQL

AselfjoininMySQLinvolvesjoiningatablewithitselfusingaliasestocomparerowswithinthesametable,particularlyusefulforhierarchicalorrelationaldata;forexample,tofindemployeesandtheirmanagers,useaLEFTJOINwithtablealiases:1.Aliasthetableas'e'foremployeesand'm

Aug 13, 2025 am 12:47 AM

How to use UNION and UNION ALL in MySQL?

UNIONremovesduplicateswhileUNIONALLincludesallrows,evenduplicates;2.UseUNIONwhendistinctresultsareneeded,suchascombininguserlistswithoutredundancy;3.UseUNIONALLwhenperformanceiscriticalordataisalreadyunique,likeaggregatinglogs;4.Bothrequirethesamenum

Aug 13, 2025 am 12:28 AM

How to use the ON DUPLICATE KEY UPDATE statement in MySQL

ONDUPLICATEKEYUPDATE is used in MySQL to handle unique key conflicts. 1. When there is a primary key or unique constraint conflict in the insert row, an update is performed instead of an error is reported; 2. Use VALUES (column) to refer to the insert value, and can update specific fields in combination with expressions; 3. Applicable to counters, upsert operations and batch data import; 4. Only trigger unique key conflicts, and updates each row at most once; 5. Different from INSERTIGNORE (ignore) and REPLACE (delete and insert), it is more efficient and safe; 6. It is necessary to ensure that the table has a correct unique index, and pay attention to the self-increment field behavior; this mechanism reduces database round trips and improves performance.

Aug 12, 2025 pm 04:04 PM

How to use aggregate functions in MySQL?

The aggregation function in MySQL is used to calculate the data and return a single value, often used in conjunction with the GROUPBY clause to summarize the data. 1. The COUNT() function can count row counts. COUNT(*) contains NULL values. COUNT(column name) only counts non-NULL values; 2. SUM() and AVG() respectively calculate the sum and average of the numeric columns, and can control the decimal places in combination with the ROUND() function; 3. MAX() and MIN() return the maximum and minimum values, which are suitable for numerical, date and other types; 4. Use GROUPBY to group by specified columns, and apply aggregate functions to each group to implement classification statistics; 5. Use the HAVING clause to filter the results after grouping, and WHERE is used for row filtering before grouping

Aug 12, 2025 pm 04:01 PM

mysql aggregate function

How to use the IN operator in MySQL?

TheINoperatorinMySQLchecksifavaluematchesanyinaspecifiedlist,simplifyingmultipleORconditions;itworkswithliterals,strings,dates,andsubqueries,improvesqueryreadability,performswellonindexedcolumns,supportsNOTIN(withcautionforNULLs),andcanbecombinedwith

Aug 12, 2025 pm 03:46 PM

mysql IN操作符

Designing MySQL Databases for Billing and Subscription Services

When designing MySQL databases for billing and subscription services, the core goal is to ensure data accuracy, scalability, and query efficiency. 1. Use the intermediate table user_subscriptions to manage many-to-many relationships between users and subscription plans, and support history; 2. Bills record each deduction information, and indexes are established according to user_id and due_date for easy query; 3. Payment records separate table payments, supporting multiple payment methods and refund processing; 4. Automatically update subscription status through timed tasks, generate bills and trigger notifications; 5. Reasonably design index and table structure to improve performance and maintenance. Good database design helps the system stay stable and efficient when user growth and function expansion

Aug 12, 2025 pm 03:00 PM