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Home

Technical Articles

Database

Mysql Tutorial

How to manage character encoding issues like utf8mb4 in MySQL?

To properly handle character encoding issues in MySQL, utf8mb4 must be used to support full UTF-8 characters such as emoji and 4-byte Unicode. 1. Use the utf8mb4 character set and utf8mb4_unicode_ci collation when creating or modifying the database; 2. Update the encoding of existing tables and columns to utf8mb4 through the ALTERTABLE and MODIFY commands; 3. Set the default character set of client, mysql and mysqld parts to utf8mb4 in the MySQL configuration file, and enable character-set-client-handshake=FALSE; 4.

Aug 17, 2025 am 04:52 AM

How to reset the root password in MySQL

StoptheMySQLserviceusingtheappropriatecommandforyoursystem.2.StartMySQLinsafemodewith--skip-grant-tablesand--skip-networkingtodisableauthenticationandremoteaccess.3.ConnecttoMySQLasrootwithoutapassword.4.ResettherootpasswordusingALTERUSERforMySQL5.7.

Aug 17, 2025 am 04:36 AM

How to work with date and time functions in MySQL?

MySQLsupportsDATE,TIME,DATETIME,TIMESTAMP,andYEARdatatypesforhandlingdateandtimevalues,withfunctionslikeNOW(),CURDATE(),andCURTIME()toretrievecurrentdateandtime,extractionfunctionssuchasYEAR(),MONTH(),andDAYNAME()toobtainspecificparts,DATE_FORMAT()fo

Aug 17, 2025 am 04:27 AM

mysql datetime function

How to create a function in MySQL

Tocreateauser-definedfunctioninMySQL,usetheCREATEFUNCTIONstatementwithpropersyntaxandDELIMITER.2.Definethefunctionwithaname,parameters,returntype,andcharacteristicslikeDETERMINISTICorREADSSQLDATA.3.WritethefunctionlogicwithinBEGIN...ENDblock,ensuring

Aug 17, 2025 am 02:54 AM

Optimizing MySQL for Large-Scale User Registrations

Tohandlelarge-scaleuserregistrationsinMySQL,useInnoDBasthestorageengineforrow-levellockingandcrashrecovery,avoidMyISAMduetotable-levellocking,enableinnodb_file_per_tableforeasiermanagement,andusefastdiskslikeSSDsorNVMe.Optimizetheschemabykeepingtheus

Aug 17, 2025 am 01:32 AM

What is the difference between CHAR and VARCHAR in MySQL?

CHAR is a fixed length, VARCHAR is a variable length; CHAR will fill the specified length with spaces and may waste spaces, while VARCHAR only uses the actual required space and retains the tail spaces; CHAR is up to 255 characters, VARCHAR can reach 65535; usually short and fixed length use CHAR, and variable length use VARCHAR.

Aug 17, 2025 am 01:27 AM

How to write a loop in a MySQL stored procedure

MySQLstoredproceduressupportthreelooptypes:1.WHILEcheckstheconditionbeforeeachiteration,makingitidealforuncertainiterationcounts;2.REPEATexecutesatleastonceandcheckstheconditionafterward;3.LOOPprovidesmanualcontrolusingLEAVEtoexitandITERATEtoskiptoth

Aug 17, 2025 am 12:10 AM

cycle

How to find tables with a specific column name in MySQL?

To find a table containing a specific column name, you should query the INFORMATION_SCHEMA.COLUMNS table; execute SELECTTABLE_NAMEFROMINFORMATION_SCHEMA.COLUMNSWHERECOLUMN_NAME='your_column_name'ANDTABLE_SCHEMA='your_database_name'; you can find all tables containing that column in the specified database, such as looking for tables containing an email column in sales_db; to search across all databases, omit the TABLE_SCHEMA condition and select to return TABLE_NAME at the same time.

Aug 16, 2025 am 11:29 AM

How to pivot data in MySQL (rows to columns)?

To implement row-to-column conversion (i.e. pivot table) in MySQL, conditional aggregation is required to be combined with GROUPBY; 1. Use SUM (CASE...) or MAX (CASE...) combined with GROUPBY to convert row data into columns, which is suitable for known column values; 2. When the column value is not fixed, dynamic SQL is generated through GROUP_CONCAT and executed with PREPARE, pay attention to adjusting group_concat_max_len; 3. IF can be used to replace CASE to simplify syntax, but CASE is still recommended; always use aggregate function, missing values are filled with 0 or NULL, text data is MAX instead of SUM, and finally perspective is completed through grouping and conditional logic.

Aug 16, 2025 am 10:54 AM

How to implement pagination in MySQL

Using LIMIT and OFFSET is the basic method of MySQL paging, which is suitable for small and medium-sized data volumes; for large-scale data or deep paging, index column-based key set paging (such as WHEREid>last_seen_id) should be used to improve performance. Both methods need to ensure the consistency of sorting through ORDERBY. The final choice depends on whether the application scenario needs random page jumps or supports infinite scrolling.

Aug 16, 2025 am 10:50 AM

How to get the last inserted ID in MySQL?

To get the last inserted ID in MySQL, you should use the LAST_INSERT_ID() function. This function returns the last self-increment ID in the current session after insertion. It has session security and is not affected by other clients. It can still obtain the correct result even after executing other queries. If no insertion occurs, it will return 0. For multi-line insertion, return the first generated ID, such as executing INSERTINTOusers(name,email)VALUES('JohnDoe','john@example.com'); followed by SELECTLAST_INSERT_ID(); to obtain the ID of the newly inserted user. When using PHP, you can use $mysqli-&

Aug 16, 2025 am 10:38 AM

mysql

How to use MATCH() AGAINST() for full-text search in MySQL

FULLTEXT index must be created for the text column first, otherwise MATCH()...AGAINST() will report an error; 2. After creating the index, you can use natural language mode, Boolean mode or query extension to search. The natural language mode is sorted by correlation by default. Boolean mode supports operators such as , -, "", *, etc., and query extensions can automatically include related words; 3. Note that MySQL ignores words and common stop words with less than 4 characters by default, and only MyISAM and InnoDB (5.6) support it; 4. To improve performance, FULLTEXT index should be used on text columns to avoid using MATCH() in complex expressions, and Boolean mode is preferred for large data sets, and finally

Aug 16, 2025 am 10:30 AM

How to create a stored procedure in MySQL

To create MySQL stored procedures, you need to use the CREATEPROCEDURE statement and process the delimiter correctly; 1. Use DELIMITER$$ to change the delimiter; 2. Create stored procedures with parameters (IN, OUT, INOUT), including SQL logic in BEGIN...END; 3. Use DELIMITER; restore the delimiter; 4. Use CALL statement to call stored procedures; 5. Complex logic can be implemented in combination with IF, WHILE and other control structures; 6. It is recommended to use DROPPROCEDUREIFEXISTS to avoid duplicate errors; 7. Keep the naming clear and add comments to improve readability. After the entire process is completed, the stored procedure can be successfully created and called.

Aug 16, 2025 am 10:26 AM

mysql stored procedure

What is the purpose of the foreign key ON DELETE CASCADE in MySQL?

ThepurposeoftheONDELETECASCADEoptioninaforeignkeyconstraintinMySQListoautomaticallydeleterowsinachildtablewhenthecorrespondingrowintheparenttableisdeleted,ensuringreferentialintegritybypropagatingdeletionsfromtheparenttothechildtable;forexample,delet

Aug 16, 2025 am 09:47 AM