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- How to get the row count for all tables in a MySQL database?
- Use INFORMATION_SCHEMA to quickly obtain the estimated row count of each table in the MySQL database, which is suitable for MyISAM and InnoDB; and the exact row count can be obtained through COUNT(*) query, but the speed is slow, which is suitable for scenarios with high accuracy requirements.
- Mysql Tutorial . Database 706 2025-09-12 00:10:01
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- How to Configure the MySQL Buffer Pool for Optimal Performance?
- To optimize MySQL performance, the InnoDB buffer pool must be configured correctly. First, set innodb_buffer_pool_size to 70-80% of the RAM of the dedicated server, such as 16GB of memory to 12G, to ensure that the cache hit rate exceeds 95%. Second, when the buffer pool is large, set innodb_buffer_pool_instances to 8 to reduce contention; then, enable innodb_buffer_pool_dump_at_shutdown and innodb_buffer_pool_load_at_startup to quickly restore cached data after restart; finally, monitor the buffer pool hit rate regularly,
- Mysql Tutorial . Database 848 2025-09-11 14:10:01
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- How to update a view in MySQL
- Toupdateaview'sdefinitioninMySQL,useALTERVIEWorCREATEORREPLACEVIEWtomodifyitsunderlyingquery.2.Toupdatedatathroughaview,useUPDATE,INSERT,orDELETEstatementsiftheviewisupdatable,whichrequiresittonotuseDISTINCT,GROUPBY,HAVING,aggregates,JOINs,subqueries
- Mysql Tutorial . Database 652 2025-09-11 11:01:00
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- How to get table schema information in MySQL?
- UseDESCRIBEorDESCtoquicklyviewcolumndetailslikename,type,andkeyinfo.2.QueryINFORMATION_SCHEMA.COLUMNSforcustomizable,detailedmetadata.3.UseSHOWCREATETABLEtoseethefulltablecreationSQL.4.UseSHOWINDEXtoretrieveindexinformation.
- Mysql Tutorial . Database 932 2025-09-11 10:48:02
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- What is the performance_schema database in MySQL?
- Theperformance_schemadatabaseinMySQLprovidesreal-timeperformancemonitoringanddiagnosticsbytrackingserveractivitiessuchasSQLstatementexecution,threadbehavior,fileI/O,tableaccess,locks,memoryusage,andwaitevents;unlikeINFORMATION_SCHEMA,whichstoresmetad
- Mysql Tutorial . Database 397 2025-09-11 10:26:01
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- How to Deal with 'Too Many Connections' Error in MySQL?
- CheckcurrentconnectionusagewithSHOWVARIABLESLIKE'max_connections'andSHOWSTATUSLIKE'Threads_connected'toconfirmifthelimitisreached.2.TemporarilyincreasethelimitusingSETGLOBALmax_connections=500toallowimmediateconnections.3.Optimizeapplicationbehaviorb
- Mysql Tutorial . Database 532 2025-09-11 09:36:02
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- How to create a foreign key in MySQL?
- TocreateaforeignkeyinMySQL,defineacolumnreferencinganothertable’sprimaryoruniquekeyusingFOREIGNKEYinCREATETABLEorALTERTABLE,ensuringmatchingdatatypes,InnoDBengine,andindexedreferencedcolumns.
- Mysql Tutorial . Database 296 2025-09-11 09:25:01
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- How to check the status of MySQL replication
- RunSHOWSLAVESTATUS\Gonthereplicatocheckreplicationstatus.2.VerifySlave_IO_Running:Yes,Slave_SQL_Running:Yes,Seconds_Behind_Masterislowor0,andnoerrorsinLast_Errororrelatedfields.3.Useperformance_schemaqueriesinMySQL5.7 fordetailedthreadstatus.4.Option
- Mysql Tutorial . Database 807 2025-09-11 00:01:13
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- Building ETL Pipelines with MySQL and Other Data Sources
- TobuildanETLpipelinethatpullsdatafrommultiplesources,transformsit,andloadsitintoMySQL,followthesesteps:1)Understandyourdatasources,includingMySQL(assourceortarget),APIs,CSVfiles,andotherdatabases.2)ChooseappropriatetoolslikePythonwithPandas/SQLAlchem
- Mysql Tutorial . Database 535 2025-09-10 06:53:00
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- How to use cursors in MySQL stored procedures
- When using cursors, you must first declare the variable, then declare the cursor, and finally declare the processor. 1. Declare the variable and NOTFOUND processor; 2. Declare the cursor and associate the SELECT statement; 3. Open the cursor; 4. Get data in the loop and process it; 5. Close the cursor; it must be executed in this order and ensure that resources are cleaned. Cursors are only used in scenarios that must be processed line by line. Due to the low performance, set operations should be used to complete tasks first and end with a complete sentence structure.
- Mysql Tutorial . Database 485 2025-09-10 06:52:01
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- How to create a primary key in MySQL?
- Defining primary keys can ensure data integrity. When creating tables, you can use PRIMARYKEY constraints to specify single column or multiple column key combinations, such as CREATETABLEusers(idINTPRIMARYKEY, nameVARCHAR(50)); for existing tables, use ALTERTABLEusersADDPRIMARYKEY(id), but the columns must be unique and non-empty; compound primary keys are suitable for multi-column combination unique scenarios, such as PRIMARYKEY(order_id, product_id); use ALTERTABLEusersDROPPRIMARYKEY to remove primary keys.
- Mysql Tutorial . Database 581 2025-09-10 06:50:00
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- How to use regular expressions in MySQL with REGEXP
- MySQL supports basic regular expression matching using REGEXP or RLIKE operators for performing pattern-based string searches in SQL queries. 1. You can use REGEXP to implement pattern filtering in the WHERE clause. For example, SELECTFROMusersWHEREemailREGEXP'gmail' can match the lines in which the email field contains "gmail", which is not case sensitive by default; 2. Common regular elements include. (any single character), ^ (starting of string), $ (end of string), (zero or more precedent characters), (one or more),? (zero or one), [abc] (character set), [a-z] (character specimen
- Mysql Tutorial . Database 703 2025-09-10 06:34:01
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- How to use comments in MySQL queries?
- MySQL supports a variety of comment syntax to improve the readability and maintainability of SQL code. 1. Use single-line comments - (subsequent to spaces) or #, the content from the mark to the end of the line will be ignored; 2. Use /.../ for multiple lines and can be used to comment or disable code blocks, or can be used to inline comments; 3. Use /!.../ for conditional comments, the contents will be executed by MySQL but ignored by other databases, and can also be specified versions such as /!50001.../ only in MySQL 5.0.1 and above; 4. Comments can be used to document descriptions of complex queries, temporarily disable code, debugging, or writing tutorial examples, so as to help others and future selves understand SQL logic more clearly.
- Mysql Tutorial . Database 189 2025-09-10 05:20:01
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- How to find the Nth highest value in a table in MySQL
- To find the N-highest value in the table, it is recommended to use the DENSE_RANK() function, 1. Use LIMIT and OFFSET: suitable for scenarios without duplicates or small datasets, the syntax is SELECTDISTINCT column name FROM table name ORDERBY column name DESCLIMIT1OFFSETN-1; 2. Use DENSE_RANK(): suitable for processing duplicate values ??to ensure that there is no gap in ranking, the syntax is SELECT column name FROM (SELECT column name, DENSE_RANK() OVER (ORDERBY column name DESC) ASrnkFROM table name) tWHERErnk=N; 3. Use subquery: suitable for MySQL8.0 below
- Mysql Tutorial . Database 610 2025-09-10 04:18:00
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