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Technical Articles

Database

How to use prepared statements in MySQL

Using preprocessing statements can effectively prevent SQL injection and improve performance. The answer is to separate SQL structure and data to achieve safe and efficient query execution. 1. In MySQL native commands, use PREPARE, SET, EXECUTE and DEALLOCATE statements to define and execute preprocessing statements, such as PREPAREstmt_nameFROM'SELECT*FROMusersWHEREid=?'; 2. In PHP's MySQLi, use prepare() to create a statement, bind_param() to bind parameters, execute() to execute, and finally close the statement; 3. In PHP's PDO, support naming placeholders such as:id,

Sep 05, 2025 am 08:04 AM

How to find the mode (most frequent value) in SQL?

TofindthemodeinSQL,firstgroupbythecolumnandcountthefrequencyofeachvalue.2.Then,identifythemaximumfrequencyusingasubqueryorwindowfunctiontofilterforthemostfrequentvalue(s).3.UseasubqueryapproachforcompatibilityacrossallSQLdialectsorwindowfunctionslike

Sep 05, 2025 am 07:41 AM

How to find all tables with a specific column name in SQL?

To find all tables containing specific column names, it can be done by querying the system metadata table, the most common method is to use INFORMATION_SCHEMA.COLUMNS. 1. In standard SQL, execute SELECTTABLE_NAMEFROMINFORMATION_SCHEMA.COLUMNSWHERECOLUMN_NAME='your_column_name' to return all table names in the specified column. If you need to define a specific schema or database, you can add the TABLE_SCHEMA or TABLE_CATALOG conditions. 2. In SQLServer, you can use sys.columns and sys.ta

Sep 05, 2025 am 07:13 AM

sql 查找表

How to force a query to use a specific index in MySQL

USEINDEXsuggestsanindexbutallowsMySQLtoignoreitifatablescanisbetter;2.FORCEINDEXrequirestheuseofaspecificindexandpreventstablescans,whichcanimproveperformancewhentheoptimizermakespoorchoicesbutmaydegradeperformanceifmisused;3.IGNOREINDEXpreventsMySQL

Sep 05, 2025 am 06:53 AM

How to Ensure Durability of Writes in MongoDB

ToensuredurablewritesinMongoDB,usewriteconcernw:"majority"toconfirmwritesonamajorityofreplicasetmembers,enablejournaling(storage.journal.enabled:true)toprotectagainstcrashes,anddeployaproperlyconfiguredthree-memberreplicasetforfaulttoleranc

Sep 05, 2025 am 06:52 AM

mongodb Data persistence

How to Use MongoDB for E-commerce Applications

MongoDBisidealfore-commerceduetoitsflexibledocumentmodel,enablingefficientproductcatalogmanagementwithschema-freeJSON-likedocuments;itsupportsembeddeddataandarraysforproductvariants,specifications,andimages,whileindexingenhancesqueryperformanceonfiel

Sep 05, 2025 am 06:46 AM

mongodb e-commerce

How to insert data into a table with an identity column in SQL

ToinsertdataintoaSQLServertablewithanidentitycolumn,omittheidentitycolumnintheINSERTstatementforautomaticvaluegeneration,oruseSETIDENTITY_INSERTONtotemporarilyallowexplicitvalues,insertthedesireddataincludingtheidentityvalue,thenturnitoffwithSETIDENT

Sep 05, 2025 am 06:37 AM

How to improve SQL query performance?

UseindexeseffectivelybycreatingthemonWHERE,JOIN,ORDERBY,andGROUPBYcolumns,usingcompositeindexesformulti-columnfilters,andavoidingover-indexingtoreducewriteoverhead.2.Optimizequerystructurebyselectingonlyneededcolumns,avoidingfunctionsonindexedcolumns

Sep 05, 2025 am 06:15 AM

Query optimization sql performance

How to copy a database in phpMyAdmin

TocopyadatabaseinphpMyAdmin,firstcheckifthe"CopyDatabaseto"featureisavailableundertheOperationstab,selectthesourcedatabase,enterthenewdatabasename,choose"Structureanddata"withCREATE/DROPoptions,andclickGo.2.Ifthatoptionisunavailab

Sep 05, 2025 am 05:50 AM

How to rebuild an index in Oracle

UseALTERINDEXindex_nameREBUILDtorebuildanindex,whichcreatesanewcompactversionandreplacestheoldone;2.Optionallyspecifystorageparametersliketablespaceorblocksizeduringrebuild;3.UseALTERINDEXindex_nameREBUILDONLINEtoallowconcurrentDMLoperations,thoughit

Sep 05, 2025 am 05:41 AM

oracle 索引重建

How to get a list of columns for a table in MySQL

To obtain the column name of the MySQL table, there are three methods: 1. Use DESCRIBEtable_name to quickly view the basic information of the column, which is suitable for manual queries; 2. Use SHOWCOLUMNSFROMtable_name to support database and column name filtering, which is suitable for use in scripts; 3. Query the INFORMATION_SCHEMA.COLUMNS table, which can flexibly obtain detailed column information and be used in programmatic scenarios, which is a standard cross-database practice. Just select the appropriate method according to the usage scenario.

Sep 05, 2025 am 04:47 AM

What is the difference between TRUNCATE and DELETE with no WHERE clause?

TRUNCATEisfasterandmoreefficientthanDELETEwithnoWHEREclausebecauseitdeallocatesdatapagesandminimallylogstheoperation,whileDELETElogseachrowdeletionindividually,makingitslower;TRUNCATEresetsidentitycounters,doesnotfiretriggers,andmayberestrictedbyfore

Sep 05, 2025 am 04:35 AM

delete truncate

How to change a user's password in MySQL

ForMySQL5.7.6andlater,useALTERUSER'username'@'host'IDENTIFIEDBY'new_password';2.Forolderversions,useSETPASSWORDFOR'username'@'host'=PASSWORD('new_password');3.Tochangeyourownpassword,useALTERUSERUSER()IDENTIFIEDBY'new_password';4.Alternatively,usethe

Sep 05, 2025 am 04:29 AM

How to optimize a query with indexes in SQL

IdentifyslowqueriesusingEXPLAINtodetectfulltablescansandinefficientoperations.2.CreateindexesoncolumnsusedinWHERE,JOIN,andORDERBYclausestospeedupdataretrieval,butavoidover-indexingtopreventslowingdownwrites.3.Usecompositeindexesformulti-columnfilters

Sep 05, 2025 am 04:26 AM

index sql optimization