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Technical Articles

Database

How to Design a Normalized Database Schema in MySQL?

Understandthenormalforms:FirstNormalForm(1NF)requiresatomicvaluesanduniquerecords;SecondNormalForm(2NF)eliminatespartialdependenciesbyensuringnon-keyattributesdependontheentireprimarykey;ThirdNormalForm(3NF)removestransitivedependenciessonon-keyattri

Aug 05, 2025 am 01:26 AM

What is the Value Generator feature in Navicat?

Navicat'sValueGeneratorisatoolthatautomatesthecreationofrealistictestdatafordatabasetables.1.Ithelpsfilltableswithsampledatabasedonpredefinedrules,suchasgeneratingnames,emails,dates,ornumbers.2.Userscancustomizegenerationmethodspercolumn,setvaluerang

Aug 05, 2025 am 12:24 AM

How to Secure a MySQL Installation on a New Server?

Runmysql_secure_installationtosetrootpassword,removeanonymoususers,disableremoterootlogin,andremovetestdatabase.2.Ensurerootcanonlyconnectfromlocalhostbydroppingremoterootaccountsandcreatinglocalhost-onlyrootordedicatedadminusers.3.Createapplication-

Aug 05, 2025 am 12:20 AM

Troubleshooting MySQL Slow Query Issues and Root Causes

To solve the problem of slow MySQL query, the key is to locate bottlenecks and then perform targeted optimization. 1. First check whether the slow query log is enabled. If it is not enabled, you need to set slow_query_log=1, long_query_time=1 in the configuration file and specify the log path, and then restart or dynamically load the configuration; 2. Analyze the content of the slow query log, use the mysqldumpslow tool to sort by execution time, pay attention to problems such as not using indexes, returning too much data, and complex JOINs; 3. Use EXPLAIN to analyze the query execution plan, check the type, possible_keys, key, rows and Extra fields, and determine whether full table scans or high overhead occur.

Aug 05, 2025 am 12:19 AM

How to edit data in phpMyAdmin

ToeditdatainphpMyAdmin,loginandselectthedatabaseandtablefromthesidebar.2.Clickthepenciliconnexttothedesiredrow,modifythefieldvalueswhilerespectingdatatypes,andclickGotosave.3.Forbulkedits,usetheSQLtabwithanUPDATEstatement,ensuringaproperWHEREclauseto

Aug 04, 2025 pm 04:16 PM

What is the role of the information_schema database in MySQL?

Theinformation_schemaisaread-onlysystemdatabaseinMySQLthatprovidesmetadataaboutallotherdatabasesandobjects.1.Itservesasacentralsourceofmetadata,containingdetailsaboutdatabases,tables,columns,indexes,views,routines,triggers,anduserprivileges;forexampl

Aug 04, 2025 pm 03:47 PM

mysql 信息模式

Leveraging MySQL CHECK Constraints in MySQL 8.0

The CHECK constraint in MySQL8.0 does not really work because it parses but ignores the constraint; 1. It retains CHECK for compatibility and future extensions; 2. CHECK can be used as a document description; 3. Alternative methods include using triggers, application layer verification and stored procedures; 4. When using it, be careful not to rely on it for data verification. Multiple CHECK constraints are invalid, and migration scripts require additional processing, and some tools may prompt that they do not support it.

Aug 04, 2025 pm 03:35 PM

How to handle cascading deletes and updates with foreign keys in MySQL?

CascadingdeletesandupdatesinMySQLautomaticallymaintainreferentialintegritybypropagatingchangesfromparenttochildtables.2.UseONDELETECASCADEtoautomaticallydeletechildrecordswhenaparentrecordisdeleted,andONUPDATECASCADEtoupdatecorrespondingforeignkeyval

Aug 04, 2025 pm 03:33 PM

How to format dates in MySQL using DATE_FORMAT?

Date formatting in MySQL is implemented by the DATE_FORMAT() function, which converts datetime values into strings of the specified format. 1. The basic syntax is DATE_FORMAT(date,format), where date is a valid date expression and format is a string containing a format starting with %. 2. Common format characters include: %Y (four-digit year), %m (two-digit month), %d (two-digit day), %H (24-hour hours), %i (minutes), %p (AM/PM), etc. 3. Sample application: Use '%M%d,%Y' to output "January05,2025", '%m/%d/%Y' to generate the beauty of "01/05/2025"

Aug 04, 2025 pm 03:01 PM

SQL Server Distributed Transactions

A distributed transaction is a set of operations performed between multiple databases or servers, ensuring that all operations are either successful or fail. Its core is to ensure cross-system data consistency and rely on MSDTC service coordination. The steps to enable: 1. Ensure the server accesses MSDTC; 2. Open the firewall port; 3. Set up the linked server to enable distributed transactions; 4. Use the BEGINDISTRIBUTEDTRANSACTION command. Common problems include timeout deadlock, DTC configuration errors, and performance degradation. Solutions include reducing transaction operations, checking network configuration, and avoiding unnecessary queries and connection pool interference. Whether to use it depends on the scene. High consistency across systems is suitable for use. Otherwise, local transactions or asynchronous operations are recommended.

Aug 04, 2025 pm 02:59 PM

What is a FULL OUTER JOIN in SQL and how does it differ from other joins?

AFULLOUTERJOINreturnsallrowsfrombothtables,includingmatchedandunmatchedrecords,withNULLswherenomatchexists.1.ItcombinesmatchingrowslikeanINNERJOIN.2.ItincludesunmatchedrowsfromthelefttablewithNULLsforrighttablecolumns.3.Itincludesunmatchedrowsfromthe

Aug 04, 2025 pm 02:58 PM

Database Statistics and Their Impact on SQL Query Plans

The accuracy of database statistics directly affects the optimization effect of SQL query plan. Statistics are metadata about the distribution of tables and index data, including the number of rows, the number of different values, data distribution and index selectivity, etc., for the optimizer to estimate the cost of execution paths and select the optimal plan. Inaccurate statistical information will lead to problems such as misselecting the full table scan, unused indexes, improper parallel planning, and unreasonable association order. Maintenance methods include: 1. Regular update of statistical information; 2. Pay attention to high-frequency query columns; 3. Avoid over-update; 4. Use sampling to reduce overhead; 5. Pay attention to partition table configuration. Determining whether it is a statistical information problem can be achieved by checking the changes in the execution plan, index usage, result set estimation deviation and recent data changes. Mastering statistical information maintenance strategies can show

Aug 04, 2025 pm 02:45 PM

數(shù)據(jù)庫統(tǒng)計 SQL查詢計劃

What are the limitations of MySQL VIEWs?

MySQLviewshaveseverallimitationsthataffectperformanceandfunctionality:1.Theyincurperformanceoverheadbecausetheyarevirtualandre-executethebasequeryeachtime,leadingtoslowresponsesoncomplexjoinsorlargedatasets;2.Theyarenotalwaysupdatable,asMySQLrestrict

Aug 04, 2025 pm 02:28 PM

視圖限制

Oracle vs SQL Server performance comparison

Oraclegenerallyperformsbetterinlarge-scale,high-concurrencyenvironmentsduetoadvancedscalabilityfeatureslikeRACandsuperiorhandlingofcomplexworkloads,whileSQLServerexcelsinWindowsandAzureecosystemswitheasieradministrationandstrongOLTPperformance;1.Fore

Aug 04, 2025 pm 02:21 PM