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- How to use the REGEXP operator for pattern matching in MySQL?
- MySQL's REGEXP operator is used to perform regular expression pattern matching, which is more powerful than LIKE. 1. The basic syntax is SELECTcolumn_nameFROMtable_nameWHEREcolumn_nameREGEXP'pattern', which can be replaced by RLIKE; 2.^ represents the beginning of a string, $ represents the end,. To match any single character, special characters such as \\., such as \\.; 3. Common patterns include [abc] matching characters in brackets, [a-z] matching range, [^abc] matching characters in non-branches, (abc|def) matching multiple options; 4. Example: ^john matches strings starting with john, \\.
- Mysql Tutorial . Database 898 2025-08-24 09:20:01
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- What is database replication in MySQL?
- MySQLreplicationimprovesdataavailability,reliability,andperformancebycopyingdatafromamasterservertooneormoreslaveservers;itenableshighavailabilitywithfailoversupport,offloadsbackupsandreadqueriestoslaves,andreduceslatencythroughgeographicdistribution
- Mysql Tutorial . Database 141 2025-08-24 08:50:00
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- How to use the INFORMATION_SCHEMA database in MySQL
- INFORMATION_SCHEMA is a read-only system database used in MySQL to access database metadata, which contains information about tables, columns, indexes, permissions, etc.; 1. It provides views such as TABLES, COLUMNS, SCHEMATA, etc. to describe the database structure; 2. You can query all databases through SELECTSCHEMA_NAMEFROMINFORMATION_SCHEMA.SCHEMATA, or list tables and views in the specified database through TABLES table; 3. Use COLUMNS table to obtain column details of the table, such as column names, data types, and whether null values ??are allowed, etc.; 4. Get index information through STATISTICS table, KEY_
- Mysql Tutorial . Database 945 2025-08-24 08:11:01
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- How to get the list of users in a MySQL database?
- TogetalistofusersinaMySQLdatabase,executeSELECTUser,HostFROMmysql.user;afterconnectingwithaprivilegedaccount.2.Thisqueryretrievestheusernameandallowedconnectionhostfromthemysql.usertable,showingdetailslikeroot@localhostoradmin@%.3.Foradditionaluserin
- Mysql Tutorial . Database 338 2025-08-24 06:35:00
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- What is the table_open_cache setting in MySQL?
- Thetable_open_cachesettinginMySQLspecifiesthemaximumnumberofopentableinstancesthatcanbecachedtoreducetheoverheadofrepeatedlyopeningandclosingtables,improvingperformancebyreusingtablehandles;itisdistinctfromtable_definition_cache,whichcachestablemetad
- Mysql Tutorial . Database 591 2025-08-24 06:05:01
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- How to audit user activity in MySQL
- EnableGeneralQueryLogfortemporary,full-queryloggingwithhighperformanceoverhead.2.UseMySQLEnterpriseAuditpluginforrobust,filtered,JSON-formattedauditinginEnterpriseEdition.3.InstallMariaDBAuditPlugininCommunityEditionforcomprehensiveloggingofconnectio
- Mysql Tutorial . Database 825 2025-08-24 03:38:01
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- What is the MySQL Slow Query Log and How to Use It?
- TheMySQLSlowQueryLogshouldbeenabledtoidentifyandoptimizeslow-performingqueries,asitrecordsqueriesexceedingaspecifiedexecutiontimeandhelpsimprovedatabaseperformance.1.Enabletheslowquerylogbysettingslow_query_log=ONintheconfigurationfileorviaSETGLOBALs
- Mysql Tutorial . Database 188 2025-08-24 01:34:01
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- How to perform a self-join in MySQL?
- Aself-joininMySQLisaJOINwhereatableisjoinedwithitselfusingaliasestocomparerowswithinthesametable,commonlyusedforhierarchicaldatalikeemployeesandmanagersorfindingrelatedrecordssuchasemployeessharingthesamemanager,anditrequirestablealiases(e.g.,t1,t2)t
- Mysql Tutorial . Database 1026 2025-08-24 00:26:01
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- How to create a foreign key in MySQL
- TocreateaforeignkeyinMySQL,useCREATETABLEwithFOREIGNKEYreferencingaparenttable’sprimarykey,ensuringreferentialintegrity.2.Forexistingtables,useALTERTABLEADDCONSTRAINTtoaddaforeignkeywithoptionalnaming.3.RequirementsincludeusingInnoDBstorageengine,mat
- Mysql Tutorial . Database 212 2025-08-23 16:41:00
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- How to Create and Manage Users and Privileges in MySQL?
- Create a new user requires the use of the CREATEUSER statement to specify the user name, host and password, such as CREATEUSER'jane'@'localhost'IDENTIFIEDBY'SecurePass123!'; 2. Grant permissions to use GRANT statements, such as GRANTSELECT, INSERTONmydb.productsTO'jane'@'localhost', and execute FLUSHPRIVILEGES to make the changes take effect immediately; 3. View user permissions to use SHOWGRANTSFOR'username'@'host'; 4. Modify permissions to revoke specific or
- Mysql Tutorial . Database 229 2025-08-23 16:13:01
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- How to get the number of rows in a MySQL table?
- To get the number of rows in the MySQL table, the most common method is to use the COUNT() function; 1. Use COUNT() to count all rows, which is the most standard and reliable method, including rows containing NULL values. For example, SELECTCOUNT()FROMusers will return the total number of rows in the users table; 2. Use COUNT(1), the result is the same as COUNT(). Some developers use it out of habit, but there is no difference in performance in MySQL; 3. If you only count the number of rows that are not NULL in a specific column, you can use SELECTCOUNT(column_name)FROMtable_name, which will exclude rows with the column NULL; 4. You can combine WHER
- Mysql Tutorial . Database 765 2025-08-23 16:10:00
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- How to use the ENUM data type in MySQL
- ENUMinMySQLisastringobjectthatrestrictsacolumntoapredefinedlistofvalues.1.DefineENUMbylistingallowedvalues:CREATETABLEtasks(statusENUM('pending','in_progress','completed','cancelled')DEFAULT'pending');2.Insertonlyvalidstringvalues,oranerroroccursfori
- Mysql Tutorial . Database 388 2025-08-23 15:54:00
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- How to use aggregate functions in MySQL
- MySQL's aggregation function is used to calculate data and return a single value, often used in combination with GROUPBY. 1. The main functions include COUNT() (count), SUM() (sum), AVG() (average), MAX() (maximum) and MIN() (minimum), where NULL values ??are ignored except COUNT(). 2. Basic usages are as follows: COUNT() counts the total number of rows, SUM(amount) calculates the total sales, AVG(amount) calculates the average sales, MAX and MIN obtain the highest and lowest values ??respectively. 3. Use GROUPBY to group and aggregate by category, such as counting total sales by region and calculating average prices by product. 4. Make
- Mysql Tutorial . Database 561 2025-08-23 14:24:01
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- How to import a CSV file into a MySQL table?
- ThemostefficientwaytoimportaCSVfileintoaMySQLtableisusingtheLOADDATAINFILEstatement,providedthefileisaccessibletotheserverandsecure_file_privsettingsallowit;2.Beforeimporting,ensuretheCSVisproperlyformattedwithconsistentdelimiters,thetargettableexist
- Mysql Tutorial . Database 660 2025-08-23 09:27:01
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