亚洲国产日韩欧美一区二区三区,精品亚洲国产成人av在线,国产99视频精品免视看7,99国产精品久久久久久久成人热,欧美日韩亚洲国产综合乱

current location：Home > Technical Articles > Daily Programming > Mysql Knowledge

  • What is the purpose of the USE statement in MySQL?
    What is the purpose of the USE statement in MySQL?
    TheUSEstatementinMySQLselectsadefaultdatabaseforthecurrentsession,allowingsubsequentoperationstobeperformedwithinthatdatabasecontextwithoutneedingtofullyqualifytablenames;forexample,runningUSEsalessetsthesalesdatabaseasdefault,soquerieslikeSELECTFROM
    Mysql Tutorial . Database 909 2025-08-27 07:02:00
  • What is the purpose of SQL_CALC_FOUND_ROWS in MySQL?
    What is the purpose of SQL_CALC_FOUND_ROWS in MySQL?
    SQL_CALC_FOUND_ROWSwasusedtogetthetotalrowcountofaquerywithoutLIMITafterrunningaLIMITquery,enablingaccuratepaginationtotals;however,itwasdeprecatedinMySQL8.0andremovedin8.0.23duetoperformanceissues,asitforcedMySQLtoprocessallrowsdespitelimitingresult
    Mysql Tutorial . Database 218 2025-08-27 06:34:01
  • How to use INSERT IGNORE in MySQL?
    How to use INSERT IGNORE in MySQL?
    INSERTIGNOREinMySQLallowsinsertingrowswhileskippingerrorslikeduplicatekeysorNULLviolations,makingitidealforbulkinsertsordatasyncing;itconvertserrorsintowarningsinsteadofstoppingexecution,sousingSHOWWARNINGSafterwardrevealsskippedrowsduetoconstraints,
    Mysql Tutorial . Database 505 2025-08-27 05:01:01
  • What are transactions in MySQL?
    What are transactions in MySQL?
    MySQLtransactionsaresequencesofSQLstatementstreatedasasingleunitofworkthateitherfullycompletesoriscompletelyundone,ensuringdataintegrityandconsistencythroughtheACIDproperties—Atomicity,Consistency,Isolation,andDurability—whereInnoDBstorageenginesuppo
    Mysql Tutorial . Database 1033 2025-08-27 02:43:01
  • How to enable the slow query log in MySQL
    How to enable the slow query log in MySQL
    To enable MySQL slow query logs, first check the current status: 1. Execute SHOWVARIABLESLIKE'slow_query_log'; if OFF, it needs to be enabled; 2. Check the log path and threshold: SHOWVARIABLESLIKE'slow_query_log_file'; and SHOWVARIABLESLIKE'long_query_time'; 3. It is recommended to modify the configuration file (such as /etc/my.cnf), and add it under [mysqld]: slow_query_log=ON, slow_query_log_file=/var/log/mysql/m
    Mysql Tutorial . Database 506 2025-08-26 07:14:00
  • How to find the Nth highest salary in a MySQL table?
    How to find the Nth highest salary in a MySQL table?
    The use of LIMIT and OFFSET is suitable for simple queries and N is known, but does not support dynamic variables; 2. The window function using DENSE_RANK() can correctly handle duplicate values, and it is recommended to use in dynamic N scenarios in modern MySQL versions; 3. The use of related subqueries is suitable for older versions of MySQL that do not support window functions, but have poor performance; the most recommended method is DENSE_RANK(), which is suitable for most production environments due to its accuracy, flexibility and efficiency.
    Mysql Tutorial . Database 588 2025-08-26 06:42:01
  • 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 440 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 948 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 206 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 229 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 917 2025-08-25 14:17:01

Tool Recommendations

jQuery enterprise message form contact code

jQuery enterprise message form contact code is a simple and practical enterprise message form and contact us introduction page code.
form button
2024-02-29

HTML5 MP3 music box playback effects

HTML5 MP3 music box playback special effect is an mp3 music player based on HTML5 css3 to create cute music box emoticons and click the switch button.

HTML5 cool particle animation navigation menu special effects

HTML5 cool particle animation navigation menu special effect is a special effect that changes color when the navigation menu is hovered by the mouse.
Menu navigation
2024-02-29

jQuery visual form drag and drop editing code

jQuery visual form drag and drop editing code is a visual form based on jQuery and bootstrap framework.
form button
2024-02-29

Organic fruit and vegetable supplier web template Bootstrap5

An organic fruit and vegetable supplier web template-Bootstrap5
Bootstrap template
2023-02-03

Bootstrap3 multifunctional data information background management responsive web page template-Novus

Bootstrap3 multifunctional data information background management responsive web page template-Novus
backend template
2023-02-02

Real estate resource service platform web page template Bootstrap5

Real estate resource service platform web page template Bootstrap5
Bootstrap template
2023-02-02

Simple resume information web template Bootstrap4

Simple resume information web template Bootstrap4
Bootstrap template
2023-02-02

Cute summer elements vector material (EPS PNG)

This is a cute summer element vector material, including the sun, sun hat, coconut tree, bikini, airplane, watermelon, ice cream, ice cream, cold drink, swimming ring, flip-flops, pineapple, conch, shell, starfish, crab, Lemons, sunscreen, sunglasses, etc., the materials are provided in EPS and PNG formats, including JPG previews.
PNG material
2024-05-09

Four red 2023 graduation badges vector material (AI EPS PNG)

This is a red 2023 graduation badge vector material, four in total, available in AI, EPS and PNG formats, including JPG preview.
PNG material
2024-02-29

Singing bird and cart filled with flowers design spring banner vector material (AI EPS)

This is a spring banner vector material designed with singing birds and a cart full of flowers. It is available in AI and EPS formats, including JPG preview.
banner picture
2024-02-29

Golden graduation cap vector material (EPS PNG)

This is a golden graduation cap vector material, available in EPS and PNG formats, including JPG preview.
PNG material
2024-02-27

Home Decor Cleaning and Repair Service Company Website Template

Home Decoration Cleaning and Maintenance Service Company Website Template is a website template download suitable for promotional websites that provide home decoration, cleaning, maintenance and other service organizations. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-05-09

Fresh color personal resume guide page template

Fresh color matching personal job application resume guide page template is a personal job search resume work display guide page web template download suitable for fresh color matching style. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-29

Designer Creative Job Resume Web Template

Designer Creative Job Resume Web Template is a downloadable web template for personal job resume display suitable for various designer positions. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-28

Modern engineering construction company website template

The modern engineering and construction company website template is a downloadable website template suitable for promotion of the engineering and construction service industry. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-28