poronovideos黑人极品,av综合网男人的天堂,爱情岛论坛亚洲永久入口口

Article Tags

All
web3.0
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- All
- PHP Tutorial
- Python Tutorial
- Golang
- XML/RSS Tutorial
- C#.Net Tutorial
- C++
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
Database
- All
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- All
- Mac OS
- Linux Operation and Maintenance
- Apache
- Nginx
- CentOS
- Docker
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- All
- VSCode
- sublime
- notepad
- git
- composer
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- All
- Laravel
- YII
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- All
- IIS
- SEO
- Premiere
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- All
- AI
- It Industry
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- All
- WordPress
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- All
- javaTutorial
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- All
- Windows Series
- LINUX
- MAC
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
Hardware Tutorial
Mobile Tutorial
- All
- Mobile News
- iPhone
- Android Phone
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
Mobile Game Tutorial

Home

Technical Articles

Database

How to use SHOW PROCESSLIST to see running queries in MySQL

ToseecurrentlyrunningqueriesinMySQL,usetheSHOWPROCESSLISTcommand;thisdisplaysactivethreadswithdetailslikeuser,host,querystate,andexecutiontime,whereIdisthethreadID,Usertheaccountrunningthequery,Hosttheclientaddress,dbtheselecteddatabase,Commandtheope

Aug 07, 2025 pm 07:48 PM

What are the benefits of using a connection pool with MySQL?

UsingaconnectionpoolwithMySQLimprovesperformancebyreusingexistingconnections,reducingtheoverheadofrepeatedconnectionestablishmentandloweringlatency.2.Itenablesbetterresourcemanagementbylimitingconcurrentconnections,preventingthedatabasefromhittingmax

Aug 07, 2025 pm 07:42 PM

How to use the IN operator in MySQL

Use the IN operator to simplify multi-value matching query and improve readability; 1. Use IN to filter records in the specified list with literal values; 2. Use NOTIN to exclude specific values, but be careful that NULL will cause abnormal results; 3. Dynamic filtering can be implemented in combination with subqueries, such as obtaining a list of IDs that meet the conditions through subqueries; 4. In terms of performance, small to medium lists are suitable for IN, and large lists are recommended to replace them with JOIN, and it is necessary to ensure that the subquery column is indexed to avoid NOTIN and subqueries that may return NULL. At this time, NOTEXISTS should be used instead. In short, IN makes multi-value logic more concise, but NULL and performance issues need to be handled with caution.

Aug 07, 2025 pm 07:21 PM

mysql IN操作符

How to alter an existing table in SQL?

Use the ALTERTABLE statement to modify the table structure, 1. Add columns: ALTERTABLEtable_nameADDcolumn_namedata_type[constraints]; 2. Delete columns: ALTERTABLEtable_nameDROPCOLUMNcolumn_name (the data will be deleted permanently); 3. Modify column data type: MODIFY for MySQL, ALTERCOLUMNTYPE for PostgreSQL/SQLServer/Oracle; 4. Rename columns: RENAMECOLUMN for MySQL and PostgreSQL, SQLSe

Aug 07, 2025 pm 07:16 PM

sql 修改表

What is the purpose of the DISTINCT keyword in SQL?

ThepurposeoftheDISTINCTkeywordinSQListoremoveduplicaterowsfromtheresultset,returningonlyuniquevalues.1.DISTINCTfiltersoutrepeatedcombinationsofvaluesintheselectedcolumns,ensuringeachrowintheoutputisunique.2.Itoperatesontheentirecombinationofselectedc

Aug 07, 2025 pm 07:09 PM

What are Common Table Expressions (CTEs) in SQL and how are they used?

CTEsimproveSQLreadabilityandsimplifycomplexqueriesbybreakingthemintologicalsteps.1.Theysimplifycomplexqueriesbyreplacingnestedsubquerieswithcleartemporaryresultsets,asshownwhenfindingemployeesearningabovetheirdepartment’saveragesalary.2.Theyenablerec

Aug 07, 2025 pm 07:07 PM

How to escape single quotes in SQL?

To correctly handle single quotes in SQL, you need to represent single quotes in strings with two single quotes, such as 'O''Connor', which is the standard method for most databases; 1. Use two single quotes in strings to represent a literal single quote; 2. Avoid relying on backslash escapes because their behavior depends on database schema settings; 3. The best practice is to use parameterized queries, and the database driver automatically and safely handle escapes, prevent SQL injection and simplify code.

Aug 07, 2025 pm 06:53 PM

Troubleshooting MySQL Storage Space Issues

If MySQL storage space is insufficient, you need to confirm the disk usage first and then handle it in a targeted manner. 1. Use df-h to check whether the /var/lib/mysql partition is fully loaded; 2. Locate a database that takes up a large space through SQL query; 3. Further query specific large tables and consider archiving or cleaning; 4. View and clean log files, such as binary logs; 5. Configure expire_logs_days to achieve automatic cleaning; 6. Execute OPTIMIZETABLE to release the free space after deleting data; 7. Regularly clean temporary tables, historical logs and useless data; 8. Use partition tables and slice them by time; 9. Reasonably set up automatic cleaning strategies; 10. Regularly check storage status and plan expansion in advance.

Aug 07, 2025 pm 06:14 PM

mysql storage

What is the difference between a primary key and a unique key in SQL?

PrimarykeydoesnotallowNULLvalues,whileuniquekeyallowsoneNULL;2.Atablecanhaveonlyoneprimarykeybutmultipleuniquekeys;3.Primarykeyautomaticallycreatesaclusteredindex,whereasuniquekeycreatesanon-clusteredindex;4.Primarykeyisusedforidentifyingrowsandinfor

Aug 07, 2025 pm 06:01 PM

How to calculate percentile in SQL?

UsePERCENTILE_CONT(p)forexactpercentilesinPostgreSQL,SQLServer,Oracle,andMySQL8.0 ;2.UseAPPROX_PERCENTILE(col,p)forapproximateresultsinBigQueryandSpark;3.Fordatabaseswithoutbuilt-insupport,manuallycalculatepercentilesusingROW_NUMBER(),COUNT(),andinte

Aug 07, 2025 pm 05:46 PM

How do you build and execute a dynamic SQL statement safely?

Dynamic SQL can be safely executed using parameterized queries, validating whitelists, the principle of minimum permissions, and avoiding string splicing. 1. Always use parameterized execution (such as sp_executesql) to pass user data; 2. Use whitelist verification for table names, column names, etc. that cannot be parameterized and safely referenced with functions such as QUOTENAME(); 3. Limit database account permissions to reduce the impact of potential attacks; 4. Prohibit directly splicing users to input into SQL strings; 5. Priority is given to using static queries or views instead of dynamic SQL. All user input should be considered untrusted and secured through defense in depth.

Aug 07, 2025 pm 05:41 PM

How can you audit database activity in SQL?

Usebuilt-indatabaseauditfeatureslikeSQLServerAuditforSQLServer,pgAuditforPostgreSQL,andtheAuditLogPluginforMySQLtotrackuseractionsandstorelogssecurely.2.EnableSQLServerordatabaselogssuchaserrorlogsorgeneralquerylogstomonitoractivity,butlimituseofhigh

Aug 07, 2025 pm 05:28 PM

sql 數(shù)據(jù)庫(kù)審計(jì)

phpMyAdmin manage relations between tables

EnsuretablesusetheInnoDBstorageenginebycheckingtheOperationstabandselectingInnoDB.2.CreateforeignkeyconstraintsviatheRelationviewintheStructuretabbylinkingacolumn(e.g.,user_id)toareferencedcolumninanothertable(e.g.,users.id),settingONUPDATE/ONDELETEr

Aug 07, 2025 pm 05:19 PM

Can you explain the role of Oracle background processes like PMON, SMON, DBWn, LGWR, and CKPT?

Key background processes of Oracle database include PMON, SMON, DBWn, LGWR, and CKpt. PMON cleans up failed user processes, rolls back uncommitted transactions, frees resources and registers instance information; SMON is responsible for instance recovery, applies redo logs, and merges free space; DBWn writes dirty data in the buffer to data files, batch processing to reduce I/O; LGWR writes the redo log buffer to disk to ensure that transaction security records are submitted; CKpt coordinates checkpoints, notifies DBWn to write data and updates checkpoint information. These processes jointly ensure the efficient operation of the database and the consistency of data.

Aug 07, 2025 pm 04:59 PM

oracle Background process