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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
What is the best way to back up and restore a SQL database?
Logical backup is preferred for PostgreSQL and MySQL production environments: pg_dump/mysqldump combined with scripted recovery; attention must be paid to details such as consistency, permissions, parallelism, and verification. Physical backup is fast but highly complex and must be tested regularly.
Feb 03, 2026 am 04:09 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 write and debug stored procedures in Navicat for SQL Server
Navicat supports writing and debugging SQL Server stored procedures. Although there is no integrated debugger for SSMS, it can be effectively debugged through methods such as PRINT statements, temporary SELECT, parameterized tests, and TRY...CATCH error capture. It combines syntax highlighting and code completion to improve development efficiency.
Feb 03, 2026 am 04:02 AM
How to use Navicat for MariaDB? (Open-source DB guide)
Navicat is proprietary software and is not open source; when connecting to MariaDB, you need to select the "MariaDB" type, and pay attention to authentication plug-in compatibility (such as avoiding unix_socket of root@localhost), TCP user permission configuration, and SQL import restrictions.
Feb 03, 2026 am 03:59 AM
How to use Redis with Django for session management?
To configure Django to use Redis to manage sessions, you need to install django-redis and set CACHES to point to Redis; 2. Set SESSION_ENGINE to cache and SESSION_CACHE_ALIAS to default to store session data in Redis; 3. Start the Redis service and test the connection; 4. Create a view to verify the session counting function, and confirm the data storage through redis-cli.
Feb 03, 2026 am 03:57 AM
How to use the SUBSTRING function to extract text in SQL?
SUBSTRINGextractsastringportionfromastartposition(1-based)andoptionallength,usedforparsingdomains,codes,ortimestamps;syntaxvariesbyDB(e.g.,SUBSTRinMySQL/SQLite),andedgecaseslikeNULLs,negatives,orUTF-8requirecaution.
Feb 03, 2026 am 03:53 AM
How to find all tables that contain a specific column name in SQL?
PostgreSQL queries information_schema.columns to find the email column. SQL Server uses LOWER() to avoid case problems. MySQL uses LIKE with caution to prevent mismatches. Commands such as DESCRIBE cannot search across tables.
Feb 03, 2026 am 03:11 AM
How to implement full-text search with RediSearch
RediSearchenhancesRediswithfast,in-memoryfull-textsearch,supportingcomplexqueriesandautocomplete;installviaRedisStackorloadasamodule,createanindexwithFT.CREATEspecifyingfieldsliketitleandauthor,insertdatausingHSET,thensearchwithFT.SEARCHusingcriteria
Feb 03, 2026 am 03:09 AM
How to write a SQL query to get the current date and time?
Thesimplestcross-databasewayisSELECTCURRENT_TIMESTAMP;,whichisANSISQLcompliantandworksinPostgreSQL,SQLServer,Oracle,andSQLite,unlikedatabase-specificfunctionslikeNOW()(MySQL/PostgreSQLonly)orGETDATE()(SQLServeronly).
Feb 03, 2026 am 02:58 AM
How to use TRY...CATCH for Error Handling in SQL? (SQL Server Example)
SQLServer’sTRY...CATCHhandlesruntimeerrors(severity11–19)gracefullybytransferringcontroltoCATCHonerror,enablinguseofERROR_*functionsfordiagnosticsandrequiringXACT_STATE()checksforpropertransactionhandling.
Feb 03, 2026 am 02:52 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
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