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- What is the purpose of the DISTINCT keyword in MySQL?
- TheDISTINCTkeywordinMySQLremovesduplicaterowsfromqueryresults,returningonlyuniquevaluesbasedontheselectedcolumns;itworksbytreatingrowsasduplicatesonlyifallselectedcolumnvaluesareidentical,includingNULLsasequal,andisappliedtosinglecolumnstoeliminatere
- Mysql Tutorial . Database 1020 2025-09-04 07:15:00
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- How to use the CURTIME function in MySQL
- CURTIME()returnsthecurrenttimeinHH:MM:SSformatwithoutthedate;1.UseSELECTCURTIME()togetthecurrentsystemtime;2.IncludeaprecisionargumentlikeCURTIME(3)forfractionalsecondsuptomicroseconds;3.InsertCURTIME()intoTIMEtypecolumnstorecordstarttimes;4.Useitinf
- Mysql Tutorial . Database 826 2025-09-04 06:51:01
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- How to handle NULL values in MySQL?
- UseISNULLorISNOTNULLtocheckforNULLvaluesbecausestandardcomparisonswith=or!=returnunknown;2.ApplyCOALESCE()orIFNULL()toreplaceNULLswithdefaultvaluesinresults;3.WrapnullablecolumnsinfunctionslikeCOALESCE()duringarithmetictopreventNULLoutcomes;4.Enforce
- Mysql Tutorial . Database 398 2025-09-04 06:47:01
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- How to create a user in MySQL
- Create a MySQL user first, first use the administrator account to log in, execute CREATEUSER to specify the user name, host and password, then give the corresponding permissions through the GRANT statement, and finally run FLUSHPRIVILEGES to take effect, 1. Connect to MySQL: mysql-uroot-p; 2. Create a user: CREATEUSER'username'@'host'IDENTIFIEDBY'password'; 3. Grant permissions: GRANTprivilege_typeONdatabase_name.table_nameTO'username'@'host'; 4. Refresh permissions: FLU
- Mysql Tutorial . Database 953 2025-09-04 02:42:01
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- How to select a database in MySQL
- UsetheUSEdatabase_name;commandtoselectadatabaseinMySQL,replacingdatabase_namewiththedesireddatabase.2.ListavailabledatabaseswithSHOWDATABASES;ifunsurewhichonesexist.3.VerifythecurrentlyselecteddatabaseusingSELECTDATABASE();whichreturnstheactivedataba
- Mysql Tutorial . Database 998 2025-09-04 00:06:01
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- How to convert a string to uppercase or lowercase in MySQL
- ToconvertastringtouppercaseorlowercaseinMySQL,usetheUPPER()andLOWER()functions.1.UseUPPER(str)toconvertastringtouppercase,e.g.,SELECTUPPER('helloworld')returnsHELLOWORLD,orapplyittoacolumnlikeSELECTUPPER(name)FROMusers.2.UseLOWER(str)toconvertastring
- Mysql Tutorial . Database 472 2025-09-03 07:01:01
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- What is the OPTIMIZE TABLE command in MySQL?
- OPTIMIZETABLEisusedtoreorganizephysicalstorageandreclaimunusedspaceafterlargedeletionsorupdates,particularlyinInnoDBandMyISAMtables;itrebuildsthetablebycopyingonlylivedata,defragmentsstorage,updatesindexstatistics,resetsauto-incrementcountersinsomeca
- Mysql Tutorial . Database 561 2025-09-03 05:54:00
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- How to optimize the MySQL server configuration for performance
- Setinnodb_buffer_pool_sizeto70–80%ofRAM(e.g.,12Gon16GBRAM)andconfigureinnodb_buffer_pool_instancesto1per1GBofbufferpool(e.g.,8for12G);keepkey_buffer_sizesmall(32–64M)unlessusingMyISAMheavily;increasetmp_table_sizeandmax_heap_table_sizeto256Mifdisk-ba
- Mysql Tutorial . Database 310 2025-09-03 05:04:00
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- How to use Common Table Expressions (CTEs) in MySQL
- ACTEisdefinedusingtheWITHclauseandactsasatemporaryresultsetforasinglequery.2.SimpleCTEsimprovereadabilitybyisolatingcalculationslikeaveragesalary.3.MultipleCTEscanbeusedinonequery,separatedbycommas,tobreaklogicintostepssuchascomputingaveragesandranki
- Mysql Tutorial . Database 624 2025-09-03 04:15:00
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- How to import a CSV file into MySQL
- Using LOADDATAINFILE is the fastest way to import CSV files into MySQL. 1. Ensure that the CSV file is formatted correctly and placed in MySQL accessible paths or use LOCAL options; 2. Create a table in MySQL that matches the CSV structure; 3. Execute the LOADDATAINFILE command and set the correct separator, quotes and line breaks, and enable local_infile if necessary; 4. If the file is local, use LOADDATALOCALINFILE; in addition, graphical import can be performed through phpMyAdmin. Pay attention to file permissions, field matching, data type, character encoding and other issues to ensure successful import.
- Mysql Tutorial . Database 828 2025-09-03 04:11:00
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- How to manage time zones in MySQL?
- Use TIMESTAMP data types and configure time zone support to effectively manage time zones in MySQL. Specific practices include: prioritizing TIMESTAMP over DATETIME to achieve automatic time zone conversion, setting the server time zone to UTC to avoid daylight saving time problems, loading the time zone table through mysql_tzinfo_to_sql to support named time zones, setting the session time zone according to user location to automatically adjust the time, using the CONVERT_TZ() function for explicit time zone conversion, and always storing timestamps in the UTC time zone to ensure data consistency, and ultimately ensuring the accuracy of time applications across regions.
- Mysql Tutorial . Database 658 2025-09-03 02:09:01
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- How to insert if not exists in MySQL (UPSERT)
- UseINSERTIGNOREtoinsertarowonlyifitdoesn'texist,silentlyskippingduplicatesbasedonauniqueconstraint;2.UseINSERT...ONDUPLICATEKEYUPDATEtoupsert,insertingifnotexistsorupdatingifitdoes;3.AvoidREPLACEINTOasitdeletesandreinserts,potentiallycausingdatalosso
- Mysql Tutorial . Database 653 2025-09-03 00:47:00
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- How to perform a boolean full-text search in MySQL
- To perform Boolean full text search, you must first create a FULLTEXT index, and then use MATCH()...AGAINST() with INBOOLEANMODE and Boolean operators; 1. Make sure that FULLTEXT index has been created for the search column, which can be implemented through ALTERTABLE or CREATETABLE; 2. Use MATCH()...AGAINST('searchterms'INBOOLEANMODE) syntax to perform searches; 3. Use (must include), - (must exclude), "(exact phrase), * (prefix wildcard), () (group), ~ (optional downright) and other operators to accurately control the results; 4
- Mysql Tutorial . Database 692 2025-09-03 00:26:01
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- How to get the current date and time in MySQL?
- To get the current date and time, you should use the NOW() function because it returns the date and time when the statement starts to execute; if it needs to be precise to the time of the function execution moment, use SYSDATE(); use CURDATE() when only the date is needed, and use CURTIME() when only the time is needed; these functions can be used to query, insert or set default values, such as CREATETABLElogs(idINTPRIMARYKEY, messageTEXT, created_atDATETIMEDEFAULTNOW());, NOW() is usually recommended unless the real-time feature of SYSDATE() is required.
- Mysql Tutorial . Database 656 2025-09-02 08:27:01
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