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Technical Articles

Database

Mysql Tutorial

How to work with different character sets and collations in MySQL

To properly handle multilingual text, you must use the utf8mb4 character set and ensure that the settings at all levels are consistent. 1. Understand character sets and sorting rules: utf8mb4 supports all Unicode characters, utf8mb4_unicode_ci is used for general case-insensitive sorting, utf8mb4_bin is used for binary precise comparison; 2. Set default character sets and sorting rules at the server level through configuration files or SETGLOBAL; 3. Specify CHARACTERSETutf8mb4 and COLLATEutf8mb4_unicode_ci when creating a database, or modify it with ALTERDATABASE; 4. Character sets and sorting can also be defined at the table and column levels.

Sep 07, 2025 am 03:17 AM

mysql character set

How to connect to a MySQL server using Python

To connect to MySQL server using Python, you need to first install mysql-connector-python or PyMySQL library, and then use the correct credentials to establish the connection. 1. Install the library: Use pipinstallmysql-connector-python or pipinstallPyMySQL. 2. Use mysql-connector-python connection: pass in host, port, user, password and database parameters through mysql.connector.connect() method, and handle exceptions in the try-except block. Execute after the connection is successful.

Sep 07, 2025 am 01:09 AM

How to delete data from a table in MySQL

To delete data from MySQL tables, you must use DELETE statements and operate with caution. 1. The basic syntax is DELETEFROMtable_nameWHERE condition; it must include a WHERE clause to specify the deletion condition, otherwise all rows will be deleted, such as DELETEFROMusersWHEREid=5; records with id 5 will be deleted. 2. Multiple rows can be deleted through wider conditions, such as DELETEFROMusersWHEREage

Sep 07, 2025 am 01:00 AM

mysql delete data

How to format the output of the mysql command-line client

Use\Gtodisplayresultsverticallyforbetterreadabilityofwiderows,especiallywhenviewingsinglerecordswithmanycolumns;2.Use--tableor--verticalcommand-lineoptionstoforcedefaulttableorverticaloutputwhenstartingtheclient;3.Use--batch(-B)modetoproducetab-separ

Sep 06, 2025 am 07:24 AM

How to create a user in MySQL?

To create a MySQL user, use the CREATEUSER statement and grant permissions. 1. Create a user using CREATEUSER'username'@'host'IDENTIFIEDBY'password'; such as 'john'@'localhost' or 'anna'@'%'. 2. Grant necessary permissions through statements such as GRANTALLPRIVILEGESONdatabase_name.*TO'user'@'host'; or GRANTSELECT. 3. Execute FLUSHPRIVILEGES; make the permissions take effect. 4. It is recommended to use a strong password, follow the principle of minimum permissions, and refer to it if necessary

Sep 06, 2025 am 06:53 AM

mysql Create user

How to use variables in MySQL stored procedures

DeclarevariablesusingDECLAREatthestartofablockwithdatatypeslikeINT,VARCHAR,etc.,andoptionalDEFAULTvalues.2.AssignvaluesusingSETforexpressionsorSELECT...INTOforqueryresults,ensuringthequeryreturnsonerow.3.UsevariablesincontrolstructureslikeIF,CASE,orl

Sep 06, 2025 am 06:42 AM

mysql stored procedure

What is the difference between LEFT JOIN and RIGHT JOIN in MySQL?

LEFTJOIN retains all rows on the left table, and RIGHTJOIN retains all rows on the right table. The two can be converted to each other by swapping the table order. For example, SELECTu.name, o.amountFROMuserssuRIGHTJOINordersoONu.id=o.user_id is equivalent to SELECTu.name, o.amountFROMordersoLEFTJOINuserssuONu.id=o.user_id. In actual use, LEFTJOIN is more common and easy to read, so RIGHTJOIN is less used, and the logic should be clear when selecting.

Sep 06, 2025 am 05:54 AM

mysql join

How to use the MAX function in MySQL

TheMAX()functionreturnsthehighestvalueinaspecifiedcolumn.2.Itcanbeusedwithnumericdata,dates,orstrings,returningthelatestdateoralphabeticallylaststring.3.UseMAX()withWHEREtofilterrowsbeforefindingthemaximum.4.UseMAX()withGROUPBYtofindthemaximumvaluepe

Sep 06, 2025 am 04:47 AM

mysql max function

What is a composite primary key in MySQL?

AcompositeprimarykeyinMySQLusesmultiplecolumnstouniquelyidentifyarow,suchas(student_id,course_id)inanenrollmentstable,wherethecombinationensuresuniquenessbecauseneithercolumnalonecan;thisenforcesNOTNULLconstraintsonbothcolumns,createsasingleclustered

Sep 06, 2025 am 03:03 AM

How to use prepared statements in MySQL

Using preprocessing statements can effectively prevent SQL injection and improve performance. The answer is to separate SQL structure and data to achieve safe and efficient query execution. 1. In MySQL native commands, use PREPARE, SET, EXECUTE and DEALLOCATE statements to define and execute preprocessing statements, such as PREPAREstmt_nameFROM'SELECT*FROMusersWHEREid=?'; 2. In PHP's MySQLi, use prepare() to create a statement, bind_param() to bind parameters, execute() to execute, and finally close the statement; 3. In PHP's PDO, support naming placeholders such as:id,

Sep 05, 2025 am 08:04 AM

How to force a query to use a specific index in MySQL

USEINDEXsuggestsanindexbutallowsMySQLtoignoreitifatablescanisbetter;2.FORCEINDEXrequirestheuseofaspecificindexandpreventstablescans,whichcanimproveperformancewhentheoptimizermakespoorchoicesbutmaydegradeperformanceifmisused;3.IGNOREINDEXpreventsMySQL

Sep 05, 2025 am 06:53 AM

How to get a list of columns for a table in MySQL

To obtain the column name of the MySQL table, there are three methods: 1. Use DESCRIBEtable_name to quickly view the basic information of the column, which is suitable for manual queries; 2. Use SHOWCOLUMNSFROMtable_name to support database and column name filtering, which is suitable for use in scripts; 3. Query the INFORMATION_SCHEMA.COLUMNS table, which can flexibly obtain detailed column information and be used in programmatic scenarios, which is a standard cross-database practice. Just select the appropriate method according to the usage scenario.

Sep 05, 2025 am 04:47 AM

What is the difference between TRUNCATE and DELETE with no WHERE clause?

TRUNCATEisfasterandmoreefficientthanDELETEwithnoWHEREclausebecauseitdeallocatesdatapagesandminimallylogstheoperation,whileDELETElogseachrowdeletionindividually,makingitslower;TRUNCATEresetsidentitycounters,doesnotfiretriggers,andmayberestrictedbyfore

Sep 05, 2025 am 04:35 AM

delete truncate

How to change a user's password in MySQL

ForMySQL5.7.6andlater,useALTERUSER'username'@'host'IDENTIFIEDBY'new_password';2.Forolderversions,useSETPASSWORDFOR'username'@'host'=PASSWORD('new_password');3.Tochangeyourownpassword,useALTERUSERUSER()IDENTIFIEDBY'new_password';4.Alternatively,usethe

Sep 05, 2025 am 04:29 AM