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  • where is my.cnf file on mac
    where is my.cnf file on mac
    MySQL configuration file my.cnf is usually located on macOS /etc/my.cnf, /usr/local/etc/my.cnf or ~/.my.cnf on macOS; 1. Confirm the location and check whether the startup command has --defaults-file parameters; 2. Use SHOWVARIABLESLIKE'config' to query the actual loading path; 3. Manually check whether the common path exists; if you cannot find the default template or new file, the restart service will take effect after adding the basic configuration; when modifying, you need to back up the original file, pay attention to syntax, permissions, restart and avoid multiple file conflicts.
    Mysql Tutorial . Database 147 2025-06-25 19:57:10
  • setup mysql on mac for local development
    setup mysql on mac for local development
    Installing MySQL on Mac can be completed through Homebrew, running brewinstallmysql and starting the service; then executing mysql_secure_installation to set the root password, delete anonymous users, prohibit remote login, etc.; then creating a development database and exclusive users to improve security; when connecting, you can use command lines, GUI tools or application code to configure it, and pay attention to troubleshooting password errors, improper host configuration, etc. 1. Install MySQL and start the service; 2. Initialize security settings; 3. Create database and users; 4. Select the appropriate way to connect; 5. Solve common connection problems. The whole process is simple but you need to pay attention to permissions and configuration details.
    Mysql Tutorial . Database 576 2025-06-25 19:41:10
  • What are the transaction isolation levels in MySQL, and which is the default?
    What are the transaction isolation levels in MySQL, and which is the default?
    MySQL's default transaction isolation level is RepeatableRead, which prevents dirty reads and non-repeatable reads through MVCC and gap locks, and avoids phantom reading in most cases; other major levels include read uncommitted (ReadUncommitted), allowing dirty reads but the fastest performance, 1. Read Committed (ReadCommitted) ensures that the submitted data is read but may encounter non-repeatable reads and phantom readings, 2. RepeatableRead default level ensures that multiple reads within the transaction are consistent, 3. Serialization (Serializable) the highest level, prevents other transactions from modifying data through locks, ensuring data integrity but sacrificing performance;
    Mysql Tutorial . Database 866 2025-06-23 15:05:11
  • What is the difference between DATABASE and SCHEMA in MySQL?
    What is the difference between DATABASE and SCHEMA in MySQL?
    InMySQL,thetermsdatabaseandschemaarenearlyinterchangeable,butcarrysubtlecontextualdifferences.2.Adatabaseisatop-levelcontainerfordataobjectsliketables,views,andprocedures,createdwithCREATEDATABASE.3.AschemainMySQLreferstoeitherthedatabaseitself—often
    Mysql Tutorial . Database 993 2025-06-22 16:45:11
  • How to check and change a table's storage engine?
    How to check and change a table's storage engine?
    To view or modify the storage engine of MySQL tables, you can use the following methods: 1. Use SHOWCREATETABLEyour_table_name; view the storage engine of a single table; 2. Use SELECTTABLE_NAME,ENGINEFROMinformation_schema.TABLESWHERETABLE_SCHEMA='your_database_name'; batch view the storage engine of all tables in the database; 3. Use ALTERTABLEyour_table_nameENGINE=new_engine_name; modify the storage engine of tables, if changed to My
    Mysql Tutorial . Database 230 2025-06-21 13:41:10
  • Why does ORDER BY sometimes make a query slow?
    Why does ORDER BY sometimes make a query slow?
    The main reasons for slowing SQL queries by adding ORDERBY include lack of indexes, excessive result sets, mixed use of JOIN and sorting, and temporary table processing problems. 1. The lack of index will cause the database to perform full sorting. Indexes should be created for the sorting sequence. Composite indexes should be used when WHERE is involved; 2. Large result sets increase the memory or disk I/O burden, and can limit the number of rows to be returned through LIMIT, avoid SELECT*, and use key set paging optimization; 3. The mixing of JOIN and ORDERBY may cause indexes to be invalid. It is necessary to ensure that the connection and sorting sequence have indexes, and try to adjust the JOIN order or get the primary key first and then associate; 4. The use of ORDERBY in subqueries may cause temporary tables to affect performance, and the sorting can be moved into subqueries and materialized derivatives.
    Mysql Tutorial . Database 783 2025-06-20 20:46:10
  • How can I tell if my query is using an index?
    How can I tell if my query is using an index?
    You can check whether the query uses an index by looking at the execution plan. In most SQL systems, the query execution method can be analyzed using the EXPLAIN or EXPLAINANALYZE command; 1. If the output shows IndexScan or Usingindexcondition, it means that the index is used; 2. If SeqScan or type:ALL appears, the index is not used; 3. In MySQL, the Extra column shows Usingwhere; Usingindex means that the overlay index is used; 4. The key column is NULL, the index is not used; 5. The lower the rows value, the better, which means the number of rows that the optimizer expects to scan; 6. The composite index needs to be paid attention to
    Mysql Tutorial . Database 582 2025-06-20 13:33:10
  • What are the information_schema and performance_schema databases used for?
    What are the information_schema and performance_schema databases used for?
    information_schema and performance_schema are MySQL system databases used to store metadata and performance metrics respectively. information_schema provides database structure information, such as tables, columns, permissions, etc., which cannot be modified and only contains structural metadata; performance_schema records performance data during the server runtime, such as query waiting, resource consumption, etc., and specific instruments are required to enable specific instruments to obtain detailed information. Use the former to dynamically query the database object structure, while the latter can be used to troubleshoot performance bottlenecks. The two have different uses but complementary, and mastering their usage is crucial to managing and optimizing MySQL.
    Mysql Tutorial . Database 585 2025-06-20 13:09:10
  • What is the principle behind a database connection pool?
    What is the principle behind a database connection pool?
    Aconnectionpoolisacacheofdatabaseconnectionsthatarekeptopenandreusedtoimproveefficiency.Insteadofopeningandclosingconnectionsforeachrequest,theapplicationborrowsaconnectionfromthepool,usesit,andthenreturnsit,reducingoverheadandimprovingperformance.Co
    Mysql Tutorial . Database 843 2025-06-20 01:07:31
  • What are the ACID properties of a MySQL transaction?
    What are the ACID properties of a MySQL transaction?
    MySQL transactions follow ACID characteristics to ensure the reliability and consistency of database transactions. First, atomicity ensures that transactions are executed as an indivisible whole, either all succeed or all fail to roll back. For example, withdrawals and deposits must be completed or not occur at the same time in the transfer operation; second, consistency ensures that transactions transition the database from one valid state to another, and maintains the correct data logic through mechanisms such as constraints and triggers; third, isolation controls the visibility of multiple transactions when concurrent execution, prevents dirty reading, non-repeatable reading and fantasy reading. MySQL supports ReadUncommitted and ReadCommi.
    Mysql Tutorial . Database 299 2025-06-20 01:06:01
  • What is a B-Tree index?
    What is a B-Tree index?
    B-Treeindexesmatterbecausetheyenablefastandefficientdataretrievalindatabasesbymaintainingsorteddataandallowinglogarithmictimecomplexityforsearch,insertion,anddeletionoperations.Theyautomaticallybalancethemselvestopreventperformancedegradationasdatais
    Mysql Tutorial . Database 455 2025-06-20 01:02:50
  • What are Common Table Expressions (CTEs) and how to use the WITH clause?
    What are Common Table Expressions (CTEs) and how to use the WITH clause?
    CTE (CommonTableExpression) is a way in SQL for defining temporary result sets, which are defined by the WITH keyword and exist only during the current query execution. Its core role is to simplify complex query structures and improve readability and maintenance. The main uses of CTE include: 1. Simplify nested queries to make multi-layer logic clear and separate; 2. Support recursive queries, suitable for processing hierarchical or tree-like data structures; 3. Replace views, providing temporary logical abstraction without changing the database structure. When using it, you should pay attention to: the scope of action of CTE is limited to the queries that follow. Multiple CTEs can be defined and naming conflicts can be avoided. The performance is comparable to subqueries and does not guarantee improvement in execution efficiency. Choose CTE or temporary table
    Mysql Tutorial . Database 822 2025-06-20 01:02:11
  • How to check the MySQL server version?
    How to check the MySQL server version?
    To view the MySQL server version, it can be implemented in various ways, as follows: 1. Execute mysql-V using the command line; 2. Log in to the MySQL client and run SELECTVERSION(); or enter status; (abbreviated as \s); 3. Execute SHOWVARIABLESLIKE'version'; obtain more accurate version information; 4. Execute SQL query version number through database connection in the program, as shown in the Python sample code.
    Mysql Tutorial . Database 957 2025-06-20 00:59:31
  • How to use the CASE WHEN statement in a query?
    How to use the CASE WHEN statement in a query?
    TheSQLCASEWHENstatementisusedtohandleconditionallogicinqueriesbyreturningdifferentresultsbasedonspecifiedconditions.Itfunctionslikeanif-elsestatementandcanbeappliedinSELECT,WHERE,ORDERBY,andHAVINGclauses.Forexample,itcanclassifysalesas“Low”,“Medium”,
    Mysql Tutorial . Database 892 2025-06-20 00:59:11

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