丰满熟女人妻一区二区三,成人区人妻精品一熟女,japanese日本熟妇多毛

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

How to use the ANY and ALL operators in MySQL

ANY returns the result that at least one value in the subquery meets the condition. 2. ALL requires that the condition holds all return values ??of the subquery; ANY is equivalent to SOME, =ANY is equivalent to IN, !=ALL is equivalent to NOTIN; use ANY to judge "at least one match", ALL judges "must match all values", and pay attention to the impact of NULL values ??on ALL. Both only support single-column subqueries.

Aug 25, 2025 pm 02:09 PM

Designing Scalable Database Schemas with MySQL

Designing a scalable MySQLschema requires following the following key points: 1. Clarify core business needs, avoid over-design, first implement the main process, and then expand on demand; 2. Use paradigms and anti-paradigms reasonably, standardize core data, moderate redundancy in common query fields and maintain consistency through triggers or application layers; 3. It is recommended to use self-incremental integers for the primary key, and the index is created based on query conditions, pay attention to the leftmost matching principle of combined indexes and field length control; 4. Plan the sub-table strategy in advance to reserve the possibility of splitting, but wait until the data volume is large before implementing horizontal or vertical sub-tables.

Aug 25, 2025 pm 02:00 PM

how to use explain in mysql

MySQL's EXPLAIN is an important tool used to analyze SQL query execution plans. 1. It uses EXPLAIN before the SELECT statement to show how the query is executed; 2. Key fields include id (operation unique identifier), type (connection type, common values ??from best to worse are system to ALL), key (actual index), rows (number of scan lines), Extra (extra information such as Usingfilesort); 3. Common optimization suggestions include checking whether the type is ALL (full table scan), confirming whether the key is used correctly, avoiding Usingfilesort or Usingtemporary, reducing complex JOINs and

Aug 25, 2025 pm 01:10 PM

How to use the OR operator in MySQL

In MySQL, the OR operator is used for record filtering in a WHERE clause that satisfies at least one condition. 1. The basic syntax of OR is SELECTcolumn1, column2FROMtable_nameWHEREcondition1ORcondition2. As long as any condition is true, the line will be returned. 2. For example, when querying dept='Sales'ORsalary>58000, Alice, Bob and Charlie are included because one of the conditions is met, while Diana does not meet any conditions are excluded. 3. When mixing OR and AND, AND has higher priority and must use brackets to clarify the logical relationship.

Aug 25, 2025 am 10:54 AM

mysql

How to write a correlated subquery in MySQL

AcorrelatedsubqueryinMySQLdependsontheouterqueryandexecutesonceperrowfromtheouterquery.2.ItiswrittenintheSELECT,WHERE,orFROMclauseandreferencesacolumnfromtheouterqueryusingaliaseslikee1ande2.3.Exampleusecasesincludefindingemployeesearningmorethanthei

Aug 25, 2025 am 08:45 AM

mysql Subquery

Optimizing MySQL for IoT and Time-Series Data

Using MySQL to process IoT and time series data requires optimization. First, design time and device-based primary keys such as (device_id, created_at), avoid increasing the ID, and partitioning according to time range to improve query efficiency; second, enable InnoDB row or table compression, set innodb_compression_level, and separate old data to save storage space; third, create (device_id, created_at) composite index, avoid over-index, use over-index and pre-aggregation to reduce query load; finally, adjust innodb_write_io_threads, increase innodb_log_file_size

Aug 25, 2025 am 07:50 AM

How to use the HAVING clause in MySQL

HAVING is used to filter the aggregation results after grouping. It must be used after GROUPBY and is suitable for conditions containing aggregation functions such as COUNT and SUM; 1. Use HAVING to filter the aggregated data, such as SUM (amount)>2500; 2. It can be shared with WHERE. WHERE filters rows first, HAVING and then filters the group; 3. If you use the aggregation conditions in WHERE, you will get an error, and you should use HAVING instead; 4. HAVING can refer to alias in SELECT and support multi-condition combinations, such as HAVINGavg_amount>900ANDnum_sales>=2; 5. HAVIN is not available without GROUPBY.

Aug 25, 2025 am 07:48 AM

How to use the JSON_OBJECT function in MySQL

JSON_OBJECT() is used in MySQL to create JSON objects from a list of key-value pairs, and is suitable for generating structured JSON data directly from a query. 1. The basic syntax is JSON_OBJECT(key1, value1, key2, value2,...), where the key must be a string or an expression that can be converted into a string, and the value can be any expression; 2. Simple examples such as SELECTJSON_OBJECT('name','Alice','age',30) return {"name":"Alice","age":30}; 3. Can combine table count

Aug 25, 2025 am 07:14 AM

How to use CROSS JOIN in MySQL?

CROSSJOIN is used in MySQL to generate Cartesian products of two tables, that is, each row of the first table and each row of the second table; 1. Used when all combinations of two sets of data need to be generated (such as product color and size); 2. Applicable to tables that have no direct association but need to be fully combined; 3. The basic syntax is SELECT*FROMtable1CROSSJOINtable2, equivalent to implicit writing but clearer; 4. In the example, the color table and the size table cross-connection generate 6 combinations; 5. Use it with caution, because 1000×1000 rows will produce millions of rows; 6. Do not use the ON clause because there is no matching key required; 7. The results can be filtered through the WHERE clause, but excessive filtering may indicate that

Aug 25, 2025 am 04:33 AM

Troubleshooting MySQL Performance Schema Configuration

PerformanceSchema has not collected data, so instruments and consumers need to be checked and enabled; 2. The performance declines significantly after activation, and eventhistory should be enabled and restricted as needed; 3. The table structure is missing or inaccessible, so version and permissions need to be confirmed; 4. The configuration restart is invalid, and global switches need to be set in the configuration file. If the query is empty, first confirm whether SELECT*FROMperformance_schema.setup_instruments and setup_consumers enable the corresponding modules. If the file I/O needs to be turned on, UPDATE; if the performance is degraded, you should avoid full opening of low-level instru.

Aug 25, 2025 am 04:12 AM

How to Use Common Table Expressions (CTEs) in MySQL?

CTEsinMySQL8.0 aretemporaryresultsetsdefinedwiththeWITHclausethatenhancequeryreadabilityandmaintainability.1.AsimpleCTEcalculatesaveragesalaryandfiltersemployeesearningmoreusingCROSSJOIN.2.MultipleCTEscanbeusedinonequery,suchascalculatingdepartmentav

Aug 25, 2025 am 03:45 AM

What is the difference between != and in MySQL?

InMySQL,!=andarefunctionallyidentical,bothmeaning"notequalto"andproducingthesameresultswithnoperformancedifference;forexample,SELECTFROMusersWHEREstatus!='active'andSELECTFROMusersWHEREstatus'active'returnthesamerowswherestatusisnot'active'

Aug 25, 2025 am 12:35 AM

How to manage sessions in MySQL?

MySQLdoesnothaveabuilt-insessionmanagementsystemlikewebapplications,butitsupportssession-levelvariablesandconnections,andcanstoreapplicationsessiondata.1.Formanagingdatabasesessions,useSHOWPROCESSLISTtoviewactiveconnections,KILL[thread_id]toterminate

Aug 24, 2025 pm 02:11 PM

mysql

What is a subquery in MySQL?

AsubqueryinMySQLisaquerynestedwithinanotherquery,usedtoretrievedataforfilteringorcomputationintheouterquery.Itexecutesfirstandreturnsresultsthattheouterqueryuses,appearinginclauseslikeSELECT,FROM,WHERE,orHAVING.Subqueriescanreturnasinglevalue(scalar)

Aug 24, 2025 pm 01:22 PM

mysql Subquery