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- How to use the IF() function in MySQL?
- The answer is that MySQL's IF() function is used to execute conditional logic in SQL queries, and the syntax is IF(condition, value_if_true, value_if_false); it returns the corresponding value according to the conditions, and is often used to generate calculated columns in SELECT statements, such as judging whether the score passes, processing NULL value replacement, or implementing multi-level scoring through nesting to improve query flexibility.
- Mysql Tutorial . Database 814 2025-09-15 04:39:01
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- How to delete records from a MySQL table?
- TodeleterecordsinMySQL,useDELETEFROMtable_nameWHEREcondition;alwaysspecifyaWHEREclausetoavoidunintendeddataloss,andtestwithSELECTfirst.Forallrows,DELETEremovesdatabutkeepsstructure,whileTRUNCATEisfasterandresetsauto-increment.Backupdataandusetransact
- Mysql Tutorial . Database 669 2025-09-15 03:34:01
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- How to find the size of a MySQL database?
- Use SQL query information_schema to get the MySQL database size. 1. Check the specified database size: SELECTtable_schemaAS'DatabaseName',ROUND(SUM(data_length index_length)/1024/1024,2)AS'Size(MB)'FROMinformation_schema.TABLESWHEREtable_schema='your_database_name'GROUPBYtable_schema; 2. Check all database sizes: SELEC
- Mysql Tutorial . Database 921 2025-09-15 03:17:00
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- How to call a stored procedure in MySQL?
- UseCALLprocedure_name()toexecuteastoredprocedureinMySQL.Forprocedureswithparameters,passinputvaluesdirectly,anduseuser-definedvariableslike@varforOUTorINOUTparameters.Alwaysincludeparentheses,ensurecorrectparametertypes,andverifyEXECUTEprivileges.Exa
- Mysql Tutorial . Database 987 2025-09-15 01:54:01
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- How to kill a running query in MySQL?
- RunSHOWFULLPROCESSLISTtoidentifytherunningqueryandnoteitsId.2.UseKILL[connection_id]toterminatetheconnectionandstopthequery,oruseKILLQUERY[connection_id]inMySQL5.7 tostoponlythequerywhilekeepingtheconnectionalive.3.Ensureyouhavethenecessaryprivileges
- Mysql Tutorial . Database 957 2025-09-15 00:29:00
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- How to use ROW_NUMBER() in MySQL
- MySQL8.0 and above support the ROW_NUMBER() window function and can be used directly; for earlier versions (such as 5.7 and earlier), it needs to be implemented through user variable simulation. 1. In MySQL8.0, use ROW_NUMBER()OVER (PARTITIONBY column ORDERBY column) to assign a unique sequence number to each row, such as ranking in descending order of amounts within the department; 2. In MySQL
- Mysql Tutorial . Database 173 2025-09-14 06:32:00
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- How to install MySQL on macOS
- InstallHomebrewusingtheprovidedterminalcommand,then2.installMySQLviabrewinstallmysql,3.startMySQLwithbrewservicesstartmysqlforautomaticbackgroundlaunch,and4.securetheinstallationusingmysql_secure_installationtosetarootpassword,removeanonymoususers,di
- Mysql Tutorial . Database 637 2025-09-14 06:11:00
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- Understanding MySQL Stored Procedure Debugging Techniques
- The key to debugging MySQL stored procedures is outputting intermediate values, logging, external tool debugging and exception handling. 1. Use SELECT output variables such as SELECTv_counterASdebug_counter; it is convenient to view the process status but requires cleaning of debugging information. 2. Create a log table sp_debug_log insert execution information to retain debugging records. 3. Use MySQLWorkbench and other tools to set breakpoints and gradually perform analysis of variable changes. 4. Declare exception handlers such as DECLAREEXITHANDLERFORSQLEXCEPTION catch errors and roll back transactions. These methods can be used in combination to efficiently troubleshoot problems in stored procedures.
- Mysql Tutorial . Database 337 2025-09-14 05:43:00
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- How to create a stored procedure in MySQL?
- Use the CREATEPROCEDURE statement to create stored procedures in MySQL, define logical blocks through DELIMITER, support parameter passing, and simplify repetitive tasks.
- Mysql Tutorial . Database 880 2025-09-14 04:41:01
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- How to use variables in a MySQL query?
- Use variables to store and reuse values, simplifying complex queries. 2. The variable starts with @ and assigns values ??with SET or SELECT, such as SET@name='John' or SELECT@total:=COUNT()FROMusers. 3. Variables can be referenced in subsequent queries, such as SELECTFROMusersWHEREage>@age.
- Mysql Tutorial . Database 378 2025-09-14 02:58:00
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- What is the wait_timeout variable in MySQL?
- Thewait_timeoutvariableinMySQLdetermineshowlongaserverthreadwaitsforactivityonanon-interactiveconnectionbeforeclosingit,withadefaulttypicallysetto28800seconds;ithelpsmanageresourcesbyclosingidleconnections,canbeadjustedgloballyorpersessionusingSETGLO
- Mysql Tutorial . Database 168 2025-09-14 02:42:01
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- How to kill a running process in MySQL?
- First, use SHOWPROCESSLIST or query information_schema.PROCESSLIST to obtain the ID of the running process, and then use KILL[ID] to terminate the process. KILLQUERY[ID] can only terminate the query and retain the connection. Pay attention to permission requirements and avoid accidentally killing critical threads.
- Mysql Tutorial . Database 600 2025-09-14 01:37:01
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- How to update records in a MySQL table?
- UsetheUPDATEstatementtomodifyexistingdatainMySQL.Specifythetablename,setnewcolumnvalues,anduseWHEREtotargetspecificrows—omittingitupdatesallrows.Forexample,UPDATEusersSETemail='john_new@example.com'WHEREid=5;changesonlyonerecord.Multiplecolumnscanbeu
- Mysql Tutorial . Database 229 2025-09-14 01:18:01
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- How to use wildcards in MySQL
- The%wildcardmatcheszeroormorecharacters,suchas'J%'fornamesstartingwithJ,'%son'fornamesendingwithson,and'%ar%'fornamescontaining'ar'.2.Thewildcardmatchesexactlyonecharacter,suchas'_an'forthree-letternameswith'an'inthelasttwopositions,and'A___y'forfive
- Mysql Tutorial . Database 406 2025-09-13 06:20:00
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