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How to find which MySQL queries are causing high CPU usage?
Use SHOWPROCESSLIST to identify long-running queries, analyze execution plans in combination with slow query logs (long_query_time=0), EXPLAINFORMAT=TREE, locate OS-level thread hotspots with pidstat/perf, and distinguish sporadic loads from systemic inefficiencies through tools such as pt-query-digest.
Feb 03, 2026 am 04:30 AM
How to concatenate multiple columns into one string in MySQL?
MySQL’sCONCAT()joinsmultiplestringslefttorightandreturnsNULLifanyargumentisNULL;useCONCAT_WS()toskipNULLs,COALESCE/IFNULLtoreplacethem,TRIMtohandlewhitespace,generatedcolumnsforindexing,andexplicitcastingforcollation/encodingsafety.
Feb 03, 2026 am 04:25 AM
How to connect to a MySQL database with Node.js? (mysql2 Example)
mysql2 is the modern recommended solution for Node.js to connect to MySQL. It supports Promise, connection pooling and prepared statements. It is recommended to use createPool instead of createConnection. Sensitive information should be read from environment variables, and errors and connection closures should be properly handled.
Feb 03, 2026 am 04:05 AM
How to use recursive CTEs to query hierarchical data in MySQL?
MySQL 8.0.1 and above support recursive CTE, but previous versions such as 5.7 do not support it; the syntax requirements must include anchor query and recursive members, use UNIONALL to connect, and pay attention to loop detection, performance optimization and index use.
Feb 03, 2026 am 02:47 AM
How to configure the MySQL query cache for better performance?
MySQL 8.0 has completely removed the query cache. Enabling query_cache_type will report an "Unknownsystem variable" error. Because of its shortcomings such as global mutex locks and full table update failures, it has been replaced by more efficient solutions such as Redis, index optimization, and application layer caching.
Feb 03, 2026 am 02:37 AM
How to use Partitions in MySQL? (Handling Big Data)
MySQL partitioning logically divides a single table into multiple physical partitions to improve query performance. However, irrelevant data can be skipped through partition pruning only when the query conditions match the partition key (such as time range), otherwise it may be slower.
Feb 03, 2026 am 02:16 AM
How to connect a PHP application to a MySQL database?
Using mysqli_connect() requires explicit error handling, explicit parameter passing, immediate setting of the utf8mb4 character set, and external credentials; queries must use mysqli_prepare() to prevent SQL injection; connections require mysqli_ping() detection and timeout; the character set must be strictly consistent between the client and the server.
Feb 03, 2026 am 01:38 AM
How to use the EXPLAIN command to analyze a MySQL query?
EXPLAINshowsMySQL’squeryexecutionplan,notresults:itrevealsindexusage(key/possible_keys),jointypes(type),rowestimates(rows/filtered),andwarningslike“Usingfilesort”;EXPLAINANALYZEaddsactualruntimemetricsbutexecutesthequery.
Feb 02, 2026 am 05:14 AM
How to monitor MySQL performance with Performance Schema?
Key PerformanceSchema tables include events_statements_summary_by_digest (locating slow/error SQL), events_waits_summary_global_by_event_name (identifying global waiting bottlenecks), table_io_waits_summary_by_table (discovering hotspot tables), and replication_applier_status_by_worker (troubleshooting parallel replication delays).
Feb 02, 2026 am 05:06 AM
How to get the first and last day of the current month in MySQL?
MySQL uses DATE_SUB(CURDATE(),INTERVAL(DAYOFMONTH(CURDATE())-1)DAY) to obtain the first day of the month, and LAST_DAY(CURDATE()) to obtain the last day of the month. The combination of the two can safely obtain the boundary date of the month.
Feb 02, 2026 am 04:22 AM
How to properly use transactions (commit and rollback) in MySQL?
UseSTARTTRANSACTIONforatomicmulti-statementoperationslikefundtransfers;itimplicitlydisablesautocommitpersessionuntilCOMMITorROLLBACK,avoidsforgottenrollbacks,andpreventsdangerouspartialupdates—unlikedefaultautocommitmode.
Feb 02, 2026 am 03:44 AM
How to work with the binary log (binlog) in MySQL?
MySQLbinaryloggingisdisabledbydefault;verifywithSELECT@@log_bin,@@binlog_formatorSHOWVARIABLESLIKE'log_bin%';enableviamy.cnfsettingslog-binandbinlog-format(preferROW),thenrestart.
Feb 02, 2026 am 03:37 AM
How to quickly install MySQL on Windows 11?
UseMySQLInstallerinsteadofmanualZIPextractionbecauseitautomaticallyhandlesdependencies,serviceregistration,andPATHsetup;skippingitcausesmissingmysqldservice,noauto-start,and“mysqldnotrecognized”errors.
Feb 02, 2026 am 03:26 AM
How to compare two tables and find the differences in MySQL?
UseLEFTJOINwithISNULLtofindrowsintableAmissingfromtableB:SELECTa.*FROMtable_aaLEFTJOINtable_bbONa.id=b.idWHEREb.idISNULL;forreliable,readableresultsregardlessofconstraints.
Feb 02, 2026 am 12:50 AM
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