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Technical Articles

Database

Mysql Tutorial

How to disable foreign key checks temporarily in MySQL?

To temporarily disable MySQL's foreign key check, you must first set SETFOREIGN_KEY_CHECKS=0; the specific steps are: 1. Execute SETFOREIGN_KEY_CHECKS=0; disable the check; 2. Execute related operations such as building tables or inserting data; 3. Execute SETFOREIGN_KEY_CHECKS=1; re-enable the check; this setting only affects the current session, must be manually restored to ensure data integrity, and should be used with caution to avoid data inconsistencies. In addition, TRUNCATE operations may still be restricted in some storage engines.

Aug 20, 2025 pm 03:32 PM

mysql foreign key

Optimizing MySQL for Data Archiving and Historical Reporting

TooptimizeMySQLfordataarchivingandhistoricalreporting,firstseparateactiveandhistoricaldata,thenapplyspecializedstorageandindexingstrategies.1.Archiveolddatabypartitioningtablesbytime,movinghistoricaldatatodedicatedtablesordatabasesusingautomationduri

Aug 20, 2025 pm 02:08 PM

mysql Data archiving

What is the GROUP_CONCAT() function in MySQL?

GROUP_CONCAT() is used in MySQL to concatenate multiple row values into a single string and group them by specifying columns or conditions. Its basic syntax is GROUP_CONCAT(column_name[ORDERBYcolumn_nameASC/DESC][SEPARATOR'custom_separator']), which is separated by commas by default. It supports ORDERBY sorting, SEPARATOR custom separator, DISTINCT deduplication, and is limited by the group_concat_max_len system variable. The default is 1024 characters, which can be separated by SETSESSIONgroup_co

Aug 20, 2025 pm 01:43 PM

How to use the REPLACE statement in MySQL

REPLACEinMySQLdeletesandinsertsarowifaduplicateuniquekeyexists,ratherthanupdatingit.2.Itshouldbeusedwhenensuringarecordwithspecificdataexists,suchasinconfigurationsettingsorcaching.3.SyntaxoptionsincludeREPLACEINTO...VALUES,SET,orSELECT.4.Unspecified

Aug 20, 2025 pm 12:19 PM

How to use auto-increment in MySQL

Auto-incrementinMySQLautomaticallygeneratesuniqueidentifiersforprimarykeys.1.DefineAUTO_INCREMENTintablecreationwithaprimarykeyintegercolumn.2.InsertrowswithoutspecifyingtheAUTO_INCREMENTcolumnbyomittingit,usingNULL,orDEFAULT.3.Retrievethelastinserte

Aug 20, 2025 am 11:23 AM

mysql 自增長

Building High-Performance Applications with MySQL Connectors

Selecting the right MySQLConnector and using it correctly can improve application performance and security. Pay attention to connection pool configuration, parameterized query and network settings. 1. Select the officially supported connector according to the language, such as Connector/J for Java, Connector/Python for Python, to ensure compatibility and security. 2. Use connection pools (such as HikariCP, SQLAlchemy) to multiplex connections and set the maximum number of connections, connection timeout and idle timeout time reasonably to optimize performance. 3. Always use parameterized queries to prevent SQL injection and improve query execution efficiency, such as using cursor.execute(& in Python

Aug 20, 2025 am 10:38 AM

mysql Performance optimization

How to use the GROUP BY clause in MySQL

GROUPBY can group the same data, often combined with aggregation functions such as COUNT() and SUM() for statistics; 2. When grouping in a single column, the same value is combined according to the specified column and the results of each group are calculated; 3. When grouping in multiple columns, grouping according to the combined values of multiple columns in turn; 4. WHERE is used to filter rows before grouping, and HAVING is used to filter the aggregate results after grouping; 5. When ONLY_FULL_GROUP_BY mode is enabled, the non-aggregated columns in SELECT must appear in GROUPBY, otherwise an error will be reported; therefore, when using GROUPBY, the syntax compliance should be ensured to achieve effective summary and analysis of the data.

Aug 20, 2025 am 07:44 AM

How to manage password expiration policies for MySQL users?

MySQLdoesnotenforcepasswordexpirationbydefault;youmustconfigureitmanuallyusingbuilt-infeatures.1.SetaglobalexpirationpolicywithSETGLOBALdefault_password_lifetime=90;andconfiguredefault_password_lifetime=90inmy.cnfforpersistence.2.Forceimmediatepasswo

Aug 20, 2025 am 07:37 AM

What are window functions in MySQL?

WindowfunctionsinMySQLwereintroducedinMySQL8.0andallowcalculationsacrossasetofrowsrelatedtothecurrentrowwithoutcollapsingtheresultintoasinglerow,enablingthedisplayofbothdetailedandaggregateddatasimultaneously,suchasshowingeachemployee'ssalaryalongsid

Aug 20, 2025 am 06:46 AM

mysql Window Functions

What is the information_schema.tables view used for in MySQL?

Theinformation_schema.tablesviewinMySQLprovidesmetadataaboutalltablesandviews,allowinguserstoquerytablenames,schemas,types,storageengines,rowcounts,andsizes;itisessentialfordatabaseinspection,administrativetasks,andtooldevelopment,withkeycolumnsinclu

Aug 20, 2025 am 06:33 AM

mysql

How to check if a database exists in MySQL

UseSHOWDATABASESLIKE'database_name'toquicklycheckforadatabase'sexistencebyname,returningaresultifitexists;2.QueryINFORMATION_SCHEMA.SCHEMATAwithSELECTSCHEMA_NAMEFROMINFORMATION_SCHEMA.SCHEMATAWHERESCHEMA_NAME='database_name'toprogrammaticallyverifyex

Aug 20, 2025 am 04:19 AM

mysql database

How to create a new user and grant permissions from the command line in MySQL?

Log in to the MySQL administrator account: Use the mysql-uroot-p command and enter the password to enter MySQLshell; 2. Create a new user: execute CREATEUSER'username'@'host'IDENTIFIEDBY'password'; specify the user name, host and strong password; 3. Grant permissions: use GRANTpermission_typeONdatabase_name.table_nameTO'username'@'host'; assign necessary permissions such as ALLPRIVILEGES, SELECT, etc.; 4. Refresh permissions: run FLUSHPRIVILEGES;

Aug 20, 2025 am 04:11 AM

How to handle temporary tables in MySQL?

Temporary tables are used in MySQL to store intermediate results in complex queries or data processing, and their life cycle is limited to the current session. 1. Use CREATETEMPORARYTABLE to create temporary tables, such as CREATETEMPORARYTABLEtemp_sales(idINTPRIMARYKEY,amountDECIMAL(10,2),sale_dateDATE)); 2. Temporary tables are only automatically deleted when the current session is visible and the session ends; 3. If the temporary table has the same name as the permanent table, the name in the current session points to the temporary table, and attention should be paid to avoid accidental occlusion; 4. Support indexes, primary keys and constraints to improve performance; 5. Commonly used in stored procedures or functions

Aug 20, 2025 am 03:45 AM

How to create a spatial index in MySQL

TocreateaspatialindexinMySQL,usetheSPATIALkeywordwithCREATEINDEXonaspatialcolumn.2.EnsurethetableusesInnoDBorMyISAMstorageengine,withInnoDBrecommended.3.Thecolumnmustbeofspatialtype(e.g.,POINT,LINESTRING,POLYGON,GEOMETRY)anddefinedasNOTNULL.4.Spatial

Aug 20, 2025 am 01:29 AM