аⅴ资源天堂资源库在线,xxxx18hd亚洲hd护士,a级国产乱理伦片

Article Tags

All
web3.0
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- All
- PHP Tutorial
- Python Tutorial
- Golang
- XML/RSS Tutorial
- C#.Net Tutorial
- C++
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
Database
- All
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- All
- Mac OS
- Linux Operation and Maintenance
- Apache
- Nginx
- CentOS
- Docker
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- All
- VSCode
- sublime
- notepad
- git
- composer
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- All
- Laravel
- YII
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- All
- IIS
- SEO
- Premiere
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- All
- AI
- It Industry
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- All
- WordPress
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- All
- javaTutorial
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- All
- Windows Series
- LINUX
- MAC
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
Hardware Tutorial
Mobile Tutorial
- All
- Mobile News
- iPhone
- Android Phone
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
Mobile Game Tutorial

Home

Technical Articles

Database

Mysql Tutorial

What is the information_schema database in MySQL?

information_schemaisaread-onlyvirtualdatabaseinMySQLthatprovidesmetadataaboutallotherdatabases;itcontainssystemviewslikeTABLES,COLUMNS,andSCHEMATAforqueryingdatabasestructure,enablingtaskssuchasfindingtableswithspecificcolumnsorlistingindexinformatio

Sep 08, 2025 am 12:57 AM

How to query a parent-child hierarchy in MySQL

MySQL supports querying parent-child hierarchy structures depending on the version: ① MySQL8.0 can use recursive CTE to traverse downwards (such as querying all subordinates of a manager) or trace upwards (such as the path from employees to CEO); ② Old versions need to use stored procedures to simulate recursion with temporary tables; ③ can load full data at the application layer to build a tree structure; ④ Optimization scheme includes using closure tables or path enumerations (such as storage /1/3/7/paths) to improve query performance, where path enumerations quickly obtain subtrees through LIKE matching, which is suitable for large-scale hierarchical data.

Sep 08, 2025 am 12:25 AM

How to use indexes to improve performance in MySQL

Using indexes can significantly improve MySQL query performance and avoid full table scanning; 2. Indexes are suitable for accelerating WHERE, JOIN, ORDERBY and GROUPBY operations, but will increase write operation overhead and storage consumption; 3. Single columns, composite, prefix, unique or overlay indexes should be created according to query requirements, pay attention to the column order of composite indexes; 4. Avoid using functions and data types on index columns to mismatch or violate the leftmost prefix principle to ensure effective use of indexes; 5. Regularly use EXPLAIN to analyze query execution plans, remove unused or duplicated indexes, and update table statistics to optimize index effects.

Sep 07, 2025 am 06:04 AM

mysql database index

What is binary logging in MySQL?

BinarylogginginMySQLisessentialforreplication,point-in-timerecovery,andauditingasitrecordsalldataandstructurechangeslikeINSERT,UPDATE,DELETE,andDDLstatements,whileexcludingSELECTandnon-modifyingtransactions;itstoreseventsinbinaryformatcontainingSQLst

Sep 07, 2025 am 05:58 AM

mysql

How to perform an UPDATE from a SELECT statement in MySQL?

SELECT cannot be used directly in UPDATE in MySQL, but it can be implemented by combining UPDATE with JOIN, subquery or derived tables. The most effective method is to use UPDATE...JOIN, for example, UPDATEemployeesJOINsalariesONemployees.id=salaries.employee_idSETemployees.salary=salaries.amount; if you need to avoid the limitation of querying the same table when modifying the table, you can wrap the subqueries in the derived table; it is usually recommended to use the JOIN method, because it is concise, efficient and easy to understand, and you should always test SELEC first in the end.

Sep 07, 2025 am 05:44 AM

How to monitor a MySQL server

Enable slow query logs and analysis to monitor query performance; 2. Monitor key indicators such as connection number, buffer pool hit rate, lock waiting and replication delay; 3. Use tools such as PerformanceSchema, PMM, Prometheus to achieve visual monitoring; 4. Set alarm rules to promptly discover CPU, disk, connection number and replication delay abnormalities; 5. Regularly conduct log rotation, query mode review and index usage analysis to optimize long-term performance; effective MySQL monitoring should combine real-time observation, historical trend analysis and automated alarms to prevent problems in advance.

Sep 07, 2025 am 05:04 AM

What are user-defined functions in MySQL?

User-definedfunctions(UDFs)inMySQLarecustomfunctionscreatedbyuserstoextenddatabasefunctionality,withthemostcommontypebeingstoredfunctionswritteninSQL.Thesefunctionsreturnasinglescalarvalue,canbedeterministicornon-deterministic,andsupportinputparamete

Sep 07, 2025 am 04:25 AM

mysql 用戶自定義函數(shù)

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