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Technical Articles

Database

What is AUTO_INCREMENT in MySQL?

AUTO_INCREMENTinMySQLautomaticallygeneratesauniqueintegerforacolumn,typicallyusedforprimarykeys,ensuringeachnewrowreceivesasequentialidentifierwithoutmanualinput;itrequiresthecolumntobeaninteger,NOTNULL,andindexed,allowsonlyonepertable,incrementsfrom

Aug 28, 2025 am 07:35 AM

mysql

How to use table hints in SQL?

Table prompts are used to override the default behavior of the query optimizer. 1. Use WITH(hint_name) syntax to specify prompts after the table name, such as SELECT*FROMtable_nameWITH(NOLOCK)WHEREcondition; 2. Common prompts include NOLOCK (allow dirty reading), READPAST (skip locked rows), HOLDLOCK (keep shared lock), UPDLOCK (using update lock), XLOCK (get exclusive lock), INDEX() (forcing specific indexes), FORCESEEK (force index lookup) and FORCESCAN (force scan); 3. Only in performance tuning, blocking issues, index optimization or

Aug 28, 2025 am 07:07 AM

sql

How to set up SSL/TLS for secure MySQL connections

CheckSSLstatususingSHOWVARIABLESLIKE'%ssl%';ensurehave_sslisYESandssl_ca,ssl_cert,ssl_keypointtovalidfiles;verifyconnectionwithSHOWSTATUSLIKE'Ssl_cipher';2.GenerateSSLcertificatesusingOpenSSLbycreatingaCAwithopensslgenrsaandopensslreq,thengenerateser

Aug 28, 2025 am 06:45 AM

How to use the STUFF function for string manipulation in SQL?

STUFF function is used to delete characters with specified positions and lengths in a string and insert new characters, 1. For example, STUFF('123-456-7890', 5, 3, 'XXX') returns '123-XXX-7890'; 2. Insert can be achieved by setting the length to 0, such as STUFF('HelloWorld', 6, 0, 'Beautiful') returns 'HelloBeautifulWorld'; 3. Replace empty strings to delete characters, such as STUFF('abcdef', 2, 3, '') returns 'af'; 4. Can be nested for complex formatting, such as adding spaces to credit card numbers to return '1234567890123456'

Aug 28, 2025 am 05:47 AM

sql STUFF函數(shù)

How to delete records from a table based on a join in SQL?

MySQL and SQLServer support DELETEt1FROMt1JOINt2 syntax to directly delete associated records; 2. PostgreSQL and Oracle recommend using DELETEFROMt1WHEREEXISTS subquery method; 3. DELETEFROMt1WHEREidIN (SELECT...) can be used in simple scenarios, but pay attention to the limitations of MySQL on subquery; 4. Before deleting all databases, SELECT should be used to verify and use transactions to protect data to avoid error deletion.

Aug 28, 2025 am 05:03 AM

What are some common performance tuning techniques for SQL queries?

UseindexesstrategicallyonWHERE,JOIN,ORDERBY,andGROUPBYcolumns,createcompositeindexesformulti-columnfilterswithproperorder,avoidover-indexing,andremoveunusedindexes.2.Optimizequerystructurebyselectingonlyneededcolumns,replacingsubquerieswithJOINs,usin

Aug 28, 2025 am 03:43 AM

How to show all tables in a database in MySQL

UsetheUSEstatementtoselectadatabase,replacingyour_database_namewiththeactualname:USEyour_database_name;2.RunSHOWTABLES;tolistalltablesintheselecteddatabase.3.Alternatively,useSHOWTABLESINyour_database_nametolisttableswithoutswitchingdatabases.4.Optio

Aug 28, 2025 am 02:25 AM

How to Implement Geospatial Queries in MongoDB

Answer: To implement MongoDB geospatial query, you need to create a 2dsphere index and use operators such as $near, $geoWithin and $geoIntersects to perform proximity, region and intersection query.

Aug 28, 2025 am 02:22 AM

How to enable the general query log in MySQL

CheckcurrentstatususingSHOWVARIABLESLIKE'general_log';ifOFF,proceed.2.EnabletemporarilywithSETGLOBALgeneral_log='ON';andsetoutputviaSETGLOBALlog_output='FILE';or'TABLE'.3.Forpermanentenablement,addgeneral_log=1,general_log_file=/var/log/mysql/general

Aug 28, 2025 am 01:56 AM

How to analyze and repair tables in MySQL

Use ANALYZETABLE to update index statistics to optimize query execution plan, which is suitable for large amounts of data changes or as regular maintenance; 2. Use CHECKTABLE to detect whether the table is damaged. MyISAM table has significant effect. InnoDB usually handles automatically but can also be checked. EXTENDED can be selected for deep scan; 3. If damage is found, use REPAIRTABLE to repair MyISAM table. InnoDB recommends that it be restored through innodb_force_recovery or backup, and backup must be restored before repair; 4. Best practices include regular maintenance, priority use of InnoDB, and automated analysis, inspection and repair operations through mysqlcheck tool to ensure the number of

Aug 28, 2025 am 01:41 AM

How to Handle Large Datasets in MongoDB

Properschemadesign,indexing,sharding,andqueryoptimizationareessentialforhandlinglargeMongoDBdatasets.Embedrelateddataforco-accessedfields,usereferencesforlargeorindependentlyupdateddata,andavoidunboundedarrays.Createstrategicindexesonfrequentlyquerie

Aug 28, 2025 am 01:40 AM

What to do if Navicat crashes frequently?

TofixNavicatcrashing,firstupdateorreinstallthelatestversion,thendisableplugins,clearcacheandconfigfiles,checksystemcompatibility,andcontactsupportwithcrashlogsifneeded.1.Checkforupdates,uninstallcurrentversion,andperformacleaninstall.2.Temporarilydis

Aug 28, 2025 am 01:37 AM

How to create relationships in the Designer view in phpMyAdmin

EnsuretablesusetheInnoDBengine,asforeignkeysarenotsupportedinMyISAM;convertviatheOperationstabifneeded.2.Createacolumninthechildtablewiththesamedatatypeandsizeastheparenttable’sprimarykey,andindexthecolumnviatheStructuretab.3.OpentheDesignerviewbysel

Aug 28, 2025 am 01:24 AM

數(shù)據(jù)庫關(guān)系

How to add a foreign key constraint in SQL

Toaddaforeignkeywhencreatingatable,usetheFOREIGNKEYclausewithintheCREATETABLEstatement,linkingacolumntoaprimaryoruniquekeyinanothertable.2.Toaddaforeignkeytoanexistingtable,useALTERTABLEwithADDCONSTRAINT,specifyingtheforeignkeycolumnanditsreferencedc

Aug 28, 2025 am 12:59 AM