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  • What is the SQL mode in MySQL?
    What is the SQL mode in MySQL?
    SQLmodeinMySQLdefineshowtheserverinterpretsSQLstatementsbycontrollingdatavalidation,syntaxcompliance,andhandlingofinvalidormissingdata,withcommonmodesincludingSTRICT_TRANS_TABLESfordataintegrity,ONLY_FULL_GROUP_BYforstandardGROUPBYbehavior,NO_ZERO_DA
    Mysql Tutorial . Database 441 2025-08-26 05:37:01
  • What is the difference between a temporary table and a table variable in MySQL?
    What is the difference between a temporary table and a table variable in MySQL?
    MySQLdoesnotsupporttablevariableslikeSQLServer;2.Theonlybuilt-inoptionfortemporaryresultsetsinMySQLisCREATETEMPORARYTABLE;3.Temporarytablesaresession-specific,supportindexesandjoins,andareautomaticallydroppedwhenthesessionends;4.User-definedvariables
    Mysql Tutorial . Database 254 2025-08-26 04:51:01
  • How to get the list of databases on a MySQL server?
    How to get the list of databases on a MySQL server?
    To get the database list on the MySQL server, the most common method is to use the SHOWDATABASES command, and after logging in to MySQL, execute SHOWDATABASES; it can display all databases that the current user has permission to access, and system databases such as information_schema, mysql, performance_schema and sys are usually listed; in addition, the same results can be obtained by querying the INFORMATION_SCHEMA.SCHEMATA table, which is suitable for scenarios where filtering or scripting operations are required, such as using SELECTSCHEMA_NAMEFROMINFORMATION_SCHEMA_SCHEMA_
    Mysql Tutorial . Database 949 2025-08-26 04:17:01
  • What is the role of my.cnf or my.ini file in MySQL?
    What is the role of my.cnf or my.ini file in MySQL?
    Themy.cnformy.inifileisessentialforcustomizingMySQLbehavior,asitallowsadministratorstocontrolserversettings,optimizeperformance,managelogs,andapplyconfigurationstospecificcomponents;withoutit,MySQLrunsondefaults,limitingperformance,security,andmonito
    Mysql Tutorial . Database 658 2025-08-26 03:49:01
  • What is a foreign key in MySQL?
    What is a foreign key in MySQL?
    AforeignkeyinMySQLisacolumnorsetofcolumnsthatreferencesaprimaryoruniquekeyinanothertabletoenforcereferentialintegrity;itensuresdataconsistencybyallowingonlyvalidvaluesfromthereferencedtable,preventsaccidentaldeletionofrelatedrecordsdependingonconstra
    Mysql Tutorial . Database 210 2025-08-26 02:49:01
  • What is the difference between COUNT(*) and COUNT(column) in MySQL?
    What is the difference between COUNT(*) and COUNT(column) in MySQL?
    COUNT()countsallrowsincludingthosewithNULLvalues,whileCOUNT(column)onlycountsrowswherethespecifiedcolumnisnotNULL.1.COUNT()includeseveryrowregardlessofNULLsandisusedtogetthetotalnumberofrows.2.COUNT(column)excludesNULLsinthespecifiedcolumnandisusedto
    Mysql Tutorial . Database 231 2025-08-26 00:56:01
  • How to use IF statements in MySQL
    How to use IF statements in MySQL
    MySQL supports two conditional logic processing methods: 1. Use the IF() function in the query, with the syntax of IF(condition, value_if_true, value_if_false), which is suitable for SELECT, UPDATE and other statements, such as returning "Pass" or "Fail" based on student scores; 2. Use IF statements in stored procedures, with the syntax of IFTHENELSEIFELSEENDIF, which is used for complex control processes, such as judging the inventory quantity and returning different messages; the two cannot be mixed, IF() is recommended for simple conditions, IF statements are used for complex logic, and CASE is recommended for multi-layer conditions to improve readability.
    Mysql Tutorial . Database 775 2025-08-25 14:55:01
  • How to partition a large table in MySQL
    How to partition a large table in MySQL
    To effectively partition MySQL large tables, first select the appropriate partition type, such as RANGE for time series data; secondly select the partition key that matches the query pattern and make sure it is included in the primary key; then regularly manage partitions, such as adding new partitions and deleting old partitions; finally ensure performance through query optimization and monitoring. 1. Select RANGE, LIST, HASH or KEY partitions, and the time data is recommended RANGE or RANGECOLUMNS; 2. The partition key should match high-frequency query conditions and avoid frequent update columns; 3. Regularly use ALTERTABLE to add, delete or reorganize partitions; 4. Ensure that the query contains partition keys to enable partition pruning, and verify the execution plan through EXPLAIN; pay attention to Inn
    Mysql Tutorial . Database 918 2025-08-25 14:17:01
  • Troubleshooting MySQL High Availability Failover
    Troubleshooting MySQL High Availability Failover
    MySQL failover problems are usually caused by master-slave replication exceptions, inaccurate detection mechanisms, VIP configuration errors, or inconsistent data. 1. The abnormal master-slave replication status will cause no available switching nodes. You need to check the Slave_IO/SQL_Running status, replication delay and errors; 2. The inaccurate fault detection mechanism may cause misjudgment, and multi-dimensional detection should be used and reasonable timeout and retry should be set; 3. The VIP does not drift correctly or the application connection configuration will cause the new master library to be still unable to access after the switch. You need to confirm the VIP binding, DNS update and connection pool reconnection mechanism; 4. The risk of data inconsistency after the switch can be alleviated through semi-synchronous replication, GTID checking and relaylog compensation mechanisms to ensure that the data before and after the switch is complete and consistent.
    Mysql Tutorial . Database 326 2025-08-25 14:10:01
  • How to use the ANY and ALL operators in MySQL
    How to use the ANY and ALL operators in MySQL
    ANY returns the result that at least one value in the subquery meets the condition. 2. ALL requires that the condition holds all return values ??of the subquery; ANY is equivalent to SOME, =ANY is equivalent to IN, !=ALL is equivalent to NOTIN; use ANY to judge "at least one match", ALL judges "must match all values", and pay attention to the impact of NULL values ??on ALL. Both only support single-column subqueries.
    Mysql Tutorial . Database 677 2025-08-25 14:09:01
  • Designing Scalable Database Schemas with MySQL
    Designing Scalable Database Schemas with MySQL
    Designing a scalable MySQLschema requires following the following key points: 1. Clarify core business needs, avoid over-design, first implement the main process, and then expand on demand; 2. Use paradigms and anti-paradigms reasonably, standardize core data, moderate redundancy in common query fields and maintain consistency through triggers or application layers; 3. It is recommended to use self-incremental integers for the primary key, and the index is created based on query conditions, pay attention to the leftmost matching principle of combined indexes and field length control; 4. Plan the sub-table strategy in advance to reserve the possibility of splitting, but wait until the data volume is large before implementing horizontal or vertical sub-tables.
    Mysql Tutorial . Database 331 2025-08-25 14:00:03
  • how to use explain in mysql
    how to use explain in mysql
    MySQL's EXPLAIN is an important tool used to analyze SQL query execution plans. 1. It uses EXPLAIN before the SELECT statement to show how the query is executed; 2. Key fields include id (operation unique identifier), type (connection type, common values ??from best to worse are system to ALL), key (actual index), rows (number of scan lines), Extra (extra information such as Usingfilesort); 3. Common optimization suggestions include checking whether the type is ALL (full table scan), confirming whether the key is used correctly, avoiding Usingfilesort or Usingtemporary, reducing complex JOINs and
    Mysql Tutorial . Database 883 2025-08-25 13:10:01
  • How to use the OR operator in MySQL
    How to use the OR operator in MySQL
    In MySQL, the OR operator is used for record filtering in a WHERE clause that satisfies at least one condition. 1. The basic syntax of OR is SELECTcolumn1, column2FROMtable_nameWHEREcondition1ORcondition2. As long as any condition is true, the line will be returned. 2. For example, when querying dept='Sales'ORsalary>58000, Alice, Bob and Charlie are included because one of the conditions is met, while Diana does not meet any conditions are excluded. 3. When mixing OR and AND, AND has higher priority and must use brackets to clarify the logical relationship.
    Mysql Tutorial . Database 954 2025-08-25 10:54:00
  • How to write a correlated subquery in MySQL
    How to write a correlated subquery in MySQL
    AcorrelatedsubqueryinMySQLdependsontheouterqueryandexecutesonceperrowfromtheouterquery.2.ItiswrittenintheSELECT,WHERE,orFROMclauseandreferencesacolumnfromtheouterqueryusingaliaseslikee1ande2.3.Exampleusecasesincludefindingemployeesearningmorethanthei
    Mysql Tutorial . Database 581 2025-08-25 08:45:02

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